1995

•

Iowa Turfgrass

Research Report
Department of Horticulture
Department of Plant Pathology
Department of Entomology
Cooperative Extension
IOWA STATE UNIVERSITY
In Cooperation with the
Iowa Turfgrass Institute

w

a

State University

OF S C I E N C E A N D T E C H N O L O G Y

University Extension

FG-463[july 1995

Introduction
N. E. Christians and D. D. Minner

The following research report is the 16th yearly publication of the results of turfgrass research projects
performed at Iowa State University. Copies of information in earlier reports are available from most of
the county extension offices in Iowa.
The 1994 season was nearly perfect for growth of cool-season grasses. It was a much better year than
1993 which was extremely wet.
For the fifth year, this research report contains a section titled "Environmental Research.” This section
is included to inform the public of our many research projects that are aimed at the many
environmental issues that face our turf industry. Of particular interest in this section are a number of
reports on the use of natural products as substitutes for synthetic herbicides.
In February 1995, Dr. Dave Minner filled the Extension and Research position that was open for one
year following Dr. Mike Agnew's departure. Mike now works for Ciba as a Senior Technical Support
Specialist and continues to support turf research at ISU through Ciba-Geigy Corporation. Dr. Minner
received his B.S. from the University of Delaware, M.S. from the University of Maryland, and Ph.D.
from Colorado State University. Before joining ISU, Dave was the Extension Turfgrass Specialist at
the University of Missouri for 10 years. Some of the research projects that Dr. Minner is developing
at Iowa State are:
1.
2.
3.
4.

Rubber topdressing to improve traffic tolerance,
Synthetic stabilizers for sand based athletic fields,
Calcined clay topdressing to reduce heat and dry spot on putting greens, and
Sub surface forced air systems for managing sand base putting greens.

Dave, and his wife Beth, also have an active interest in ornamental grasses and prairie restoration.
They have 4 children, Meghan and David 10, Sarah 8, and Chandler 6. Dave enjoys most sports and
looks forward to hunting and fishing in Iowa.
We would like to acknowledge Richard Moore, who became superintendent of the ISU Horticulture
Research Station in 1994; Jim Dickson, manager of the turf research area; Bryan Unruh, Ph.D.
graduate student; Dave Gardener, MS graduate research assistant; Dianna Liu, Post Doctoral
researcher; Barbara Bingaman, Post Doctoral researcher; Doug Campbell, research associate, and all
others employed at the field research area in the past year for their efforts in building the turf program.
Special thanks to Lori Westrum for her work in typing and helping to edit this publication.
Edited by Nick Christians and David Minner, Iowa State University, Department of Horticulture.

Table of Contents

Turfgrass Research Area Maps

1

Environmental Data

4

Species and Cultivar Trials
Results of Kentucky Bluegrass Regional Cultivar Trials - 1994

6

Recovery of Kentucky Bluegrass Cultivars Following
Summer Dormancy - 1994

12

National Perennial Ryegrass Study - 1994

13

Regional Fine Fescue Cultivar Evaluation - 1994

16

Shade Adaptation Study - 1994

18

USGA Buffalograss Trial - 1994

20

Green Height Bentgrass Cultivar Trial (Native Soil) - 1994

21

Fairway Height Bentgrass Study - 1994

22

Herbicide and Growth Regulator Studies
Preemergence Weed Control Study - 1994

23

Postemergence Crabgrass Control Study - 1994

26

1994 Dithiopyr Pre- and Postemergence Weed Control Study

29

Broadleaf Weed Control Study - 1994

32

The Effect of Two Adjuvants on Plant Response to Primo

37

Plant Growth Regulators Applied at Low Volumes of Water

39

The Effect of Spring Applications of Ethofumesate (Prograss) on a
Golf Course Fairway at Indian Creek Country Club in Nevada, Iowa

41

Turfgrass Disease and Insect Research
Evaluation of Fungicides for Control of Snow Molds on Creeping
Bentgrass at Nashua, Iowa - 1994-95

42

Evaluation of Fungicides for Control of Pink and Gray Snow Mold
at the ISU Horticulture Farm, Gilbert, IA - 1994-95
Evaluation of Fungicides for Control of Brown Patch in Creeping
Bentgrass - 1994

Y7

Evaluation of Fungicides for Control of Dollar Spot in 'Penncross'
Bentgrass - 1994

50

Evaluation of Fungicides for Control of Leaf Spot in 'Park'
Bluegrass - 1994

53

Percolation Depth and Persistence of Bacillus thuringiensis japonensis
in Soil under Various Application and Irrigation Regimes

55

Pythium Root Diseases and Disease Complexes of Creeping Bentgrass

56

Fertilizer Trials and Soil Studies
Kentucky Bluegrass Response to Fertilizer - 1994

59

Polymer Coated Urea Fertilizer Study - 1994

63

Natural Organic Rate Study - 1994

69

Natural Organic Source Study - 1994

72

Environmental Research
The Use of a Natural Product for the Preemergence Control of
Annual Weeds

75

Greenhouse Screening Study of Eleven Corn Gluten Meal Related
Samples of Their Inhibitory Activity ovn the Germination of Creeping
Bentgrass (
grostipalustris)
A

78

Field Study of Com Gluten Meal and Corn Gluten Hydrolysate for
Crabgrass Control

81

Determining Effective Rates of Different Products of Corn Gluten
Meal for Weed Control

83

The Use of Com Gluten Meal Hydrolysate as a Natural Product
for Weed Control

86

Bioactivity of a Pentapeptide Isolated from Com Gluten Hydrolysate
on the Germination of Perennial Ryegrass Seeds

89

Cellular Effects of Root Inhibiting Compounds Derived from
Com Gluten Meal

90

Environmental Research - cont.
Fate of Nitrogen Applied to Turfgrass-Covered Soil Columns

91

Fate of l5N Amended Urea in Turfgrass Biosystems

91

Comparing Chloride Transport in Undisturbed and Disturbed
Soil Columns Under Turfgrass Conditions

91

Cargill Particle Size Com Gluten Meal Study - 1994

92

A Greenhouse Study on the Environmental Requirements for
Forecasting Pythium Blight on Golf Courses

95

Managing Dry Spots on Bentgrass Putting Greens

98

Ornamental Studies
Evaluation of Deciduous Azaleas for Iowa

101

Crabapples for Iowa Landscapes

102

Shade and Ornamental Tree Trials

103

Evaluating a Gravel Bed System to Improve Survival and Growth of
Bare-Root Trees Transplanted in Mid-Summer

105

Introducing
The Iowa State University Personnel affiliated with the Turfgrass
Research Program

107

Companies and Organizations that made donations or supplied products
to the Iowa State University Turfgrass Research Program

109

Wildflower
Native Grass
Establishment Study
Vantage
KBG

KBG

Parade
KBG

Corn gluten
Weed Control
Trial

Ram I
KBG

Corn gluten
Weed Control
Trial

Reliant
Fine Fescue

Twilight
Tall Fescue

Baron

National
Kentucky
Bluegrass

Buffalo grass Management Study

Limousine
KBG

?3

Nassau
KBG

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Argyle

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Tall Fescue
Kentucky
Bluegrass
Seed Mixtures

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261,360 ft'
6.0 Acres

Fine Fescue
Cultivar Study

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Premi um
Sod
Blend

Fairway
Height
Bentgrass

Green
Height
Bentgrass

Penneagle

Penncross

Adelphi
KBG

cd H

170'

Turfgrass
Research

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K.B.G.

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170'

LIST
Study

Perennial
Ryegrass
Cultivar
Study

Kentucky
Bluegrass
Cultivar
Study

Trial

Park
KBG

170'

Common

Fertilizer
Study

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5

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Fungicide
Trial

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135'

135’

Building

Î

Ornamental Grass Trial

N

1

1984 Expansion of the Turfgrass Research Area
108,900 ft. - 2.5 Acres2

,081
A

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Total 52,272ft2
1.2 Acres

T
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East Research Area

Shade
Adaptation
Study

DAILY RAINFALL - AMES

DATE 1994

4

DAILY TEMPERATURE - AMES

DATE 1994
Solid Une = Max Dashed Une = Min

5

Species and Cultivar
Trials

Results of Kentucky
Bluegrass Regional Cultivar Trials - 1994
N. E. Christians and J. D. Dickson
The United States Department of Agriculture (USDA) has sponsored several regional Kentucky
bluegrass cultivar trials conducted at most of the northern agricultural experiment stations. The current
test consists of 62, 80, or 128 cultivars; the number depending on the year of establishment and the type
of trial. Each cultivar was replicated three times.
Three trials were underway at Iowa State University during the 1994 season. A high-maintenance study
was established in 1990 that receives 4 lb N/1000 ft2/yr and is irrigated as needed. The second trial was
established in 1985 and receives 4 lb N/1000 ft2/yr, but is non-irrigated. The third trial was established
in the fall of 1991 and is a low-maintenance study that receives 1 lb of N/1000 ft2/yr in September and is
non-irrigated. The objective of the high-maintenance study is to investigate cultivar performance under a
cultural regime similar to that used on irrigated home lawns in Iowa. The objective of the second study
is to observe the cultivar response under conditions similar to those found in non-irrigated lawns that
receive a standard lawn care program. The objective of the third study is to evaluate cultivars under
conditions similar to those maintained in a park or school ground.
The values listed under each month in Tables 1, 2 and 3 are the averages of visual quality ratings made
on three replicated plots for the three studies. Visual quality was based on a scale of 9 to 1: 9 = best
quality, 6 = lowest acceptable quality, and 1 = poorest quality. Yearly means of data from each month
were taken and are listed in the last column. The first cultivar received the highest average rating for the
entire 1994 season. The cultivars are listed in descending order of average quality.
The 1994 season provided near perfect growing conditions for Kentucky bluegrass. It was neither too
wet or too dry. This meant that there was a minimum amount of moisture stress on the non-irrigated
areas. Some irrigation was needed during the summer months, but the non-irrigated turf did not go
completely dormant at any time during the summer. Midnight was the highest ranked cultivar in the
high-maintenance trial. This variety generally does very well in high-maintenance conditions in seasons
when environmental conditions favor growth of Kentucky bluegrass. Low maintenance cultivars like
Kenblue and South Dakota Certified ranked near the bottom in the high-maintenance trial. In the highmaintenance, non-irrigated study, Midnight dropped to 28th place. This variety is not well adapted to
non-irrigated conditions and drops off in quality under moisture stress conditions. The best varieties in
1994 in this trial were Aquila, Wabash and A-34. Blacksburg, Sydsport, and Mystic also did well.
Table 1. The 1994 quality ratings for the high-maintenance, irrigated Kentucky bluegrass trial.

1
2
3
4
5
6
7
8
9
10
11
12
13

Cultivar

May

June

July

Aug

Sept

Oct

Mean

Midnight
Ascot (BA 77-279)
Belmont (798)
Eagleton
Estate
PST-A7-1877
SR 2000
Apex (Summit)
Julia
Opti-green (PST-B8-106)
Preakness (602)
PST-C-224
Blacksburg

7.3
7.0
7.0
7.0
7.0
7.0
6.7
6.3
7.0
7.0
7.0
7.0
7.3

7,7
7.7
7.3
7.3
7.3
7.7
7.7
8.0
7.3
8.0
7.0
7.7
7.7

8.0
8.0
7.7
7.7
7.3
7.3
8.0
8.0
8.0
7.3
7.7
7.3
7.7

9.0
7.7
8.0
8.8
9.0
8.7
7.3
8.3
8.0
9.0
8.7
8.7
8.7

8.7
8.3
8.7
8.3
7.7
8.0
8.3
7.7
7.7
7.0
7.7
7.7
6.7

8.3
8.0
7.7
7.7
7.7
7.3
8.0
7.3
7.7
7.3
7.7
7.3
7.0

8.2
7.8
7.7
7.7
7.7
7.7
7.7
7.6
7.6
7.6
7.6
7.6
7.5

6

14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68

Cultivar

May

June

PST-A84-405
Allure (BA 73-540)
Aspen
BA 70-131
Cardiff
Fairfax (BA 69-82)
PST-A84-803
BA 77-292
BAR VB 1169
Coventry
Miracle
Pennpro (PR-1)
Platini
PST-UD-10
PST-UD-12
Raven (BA 78-258)
Unique (PST-C-76)
WW AG 505
A-34
Able I
Alpine
Barcelona (BAR VB 1184)
Barsweet
Bartitia
EVB 13.703
Georgetown
J-333
J34-99
Princeton 104
PST-0514
Ram-1
Shamrock (H86-712)
4 Aces (PST-RE-88)
BAR VB 852
Baronie (BAR VB 985)
Caliber (J-335)
Challenger
Classic
Cobalt
Cynthia
Destiny
Eclipse
Freedom
Glade
Gnome
HV 125
Liberty
Livingston
Trenton
BA 76-305
Banff
Barblue
Barzan
Broadway
Conni

7.0
7.0
7.0
7.0
6.7
7.36.7
7.0
7.0
7.3
6.3
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.7
7.0
7.0
7.0
6.7
7.0
7.0
7.0
7.3
7.0
7.0
6.7
6.7
7.0
6.7
7.0
7.0
7.0 *
7.0
7.0
6.3
6.7
7.0
6.7
6.7
7.0
7.0
7.0
7.0
7.0
7.3
7.0

7.0
7.0
7.3
7.0
7.3
7.3
7.0
7.7
7.0
7.0
7.0
7.7
7.0
7.0
7.0
7.3
7.0
7.3
7.0
7.3
7.0
7.0
7.0
7.0
7.3
7.0
7.0
7.0
7.0
7.3
7.3
7.3
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.3
7.0
7.3
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.3

7.0
7.0
6.0
7.0
6.3

July
7.7
7.0
7.0
7.3
. 7.7
7.3
7.3
7.7
7.3
7.0
7.7
7.3
7.7
7.0
7.3
7.0
7.3
7.0
7.3
7.0
7.3
7.0
7.3
7.0
7.0
7.0
7.3
7.3
7.3
7.7
7.3
7.3
7.7
7.0
7.0
7.7
7.3
7.0
7.3
7.7
7.0
7.0
6.7
7.0
7.3
7.0
7.0
7.0
7.0
7.0
6.7
7.0
7.3
7.0
7.0

7

Aug

Sept

Oct

Mean

8.0
8.7
8.0
8.0
8.0
8.3
8.0
7.7
8.0
8.0
8.0
8.0
8.0
7.3
7.7
7.7
7.7
8.7
8.0
7.7
8.0
8.0
8.7
8.0
7.7
7.7
7.3
8.0
7.3
7.7
8.3
7.7
7.3
8.0
7.7
7.0
7.3
7.7
7.3
7.7
8.0
7.3
8.0
7.7
7.3
7.7
7.3
7.7
7.7
7.3
7.7
7.7
7.7
7.5
7.7

7.7
7.7
7.7
7.7
7.7
7.7
8.0
7.0
7.3
7.3
7.7
7.0
7.0
8.0
7.3
7.0
7.7
7.3
7.0
7.3
7.0
7.3
6.7
7.0
7.7
7.7
7.3
7.0
7.3
7.3
6.7
7.0
7.3
7.0
7.3
7.3
7.0
7.0
7.3
7.0
7.3
7.3
7.0
7.0
7.3
7.3
7.3
7.0
7.3
7.3
7.0
6.7
7.3
7.3
7.0

7.7
7.3
7.3
7.3
7.0
6.7
7.7
6.7
7.0
7.0
7.3
6.7
7.0
7.3
7.3
7.7
7.3
6.7
6.3
7.0
6.7
7.0
6.7
7.0
6.7
6.7
7.0
6.7
7.0
6.7
6.7
6.7
6.7
6.7
6.3
6.3
6.7
6.7
7.0
6.3
6.3
6.7
7.0
7.0
6.7
6.3
6.7
7.0
6.3
6.3
6.7
6.7
6.7
6.7
6.7

7.5
7.4
7.4
7.4
7.4
7.4
7.4
7.3
7.3
7.3
7.3
7.3
7.3
7.3
7.3
7.3
7.3
7.3
7.2
7.2
7.2
7.2
7.2
7.2
7.2
7.2
7.2
7.2
7.2
7.2
7.2
7.2
7.1
7.1
7.1
7.1
7.1
7.1
7.1
7.1
7.1
7.1
7.1
7.1
7.1
7.1
7.1
7.1
7.1
7.0
7.0
7.0
7.0
7.0
7.0

69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113

114
115
116
117
118
119
120
121
122
123

Cultivar

May

Dawn
Haga
J13-152
Minstrel
PST-1DW
PST-A7-341
PST-HV-116
SR 2100
Touchdown
Trampas
1757
BA 77-700
Baron
Chelsea
Crest
Fortuna
J11-94
Kelly
Limousine
Melba
Merion
Merit
Monopoly
Nassau
Nublue (J-229)
Nustar
PST-R-740
PSU-151
R751A
Suffolk
Viva (BA 73-366)
Washington
Abbey
Ampellia
BA 73-382
EVB 13.863
Indigo
Miranda
NE 80-47
PST-A84-928
Silvia
Blue Star (PST-B8-13)
Buckingham (BA 74-114)
Cannon (BA 73-381)
J-386
Noblesse
Opal
Barmax (BAR VB 7037) *
Eva (WW AG 508)
KWS PP 13-2
Ronde
Marquis
Greenley
Donna
South Dakota Cert.

7.0
7.0
7.0
6.7
7.0
6.3
7.0
7.0
6.7
6.7
7.0
7.0
7.0
6.7
6.3
7.0
7.0
7.0
7.0
7.0
7.0
6.3
7.0
6.3
7.0
7.0
7.0
7.0
6.7
7.0
7.0
6.7
7.0
7.0
7.0
7.0
6.7
6.7
7.0
6.3
7.0
6.3
6.3
5.7
6.7
6.3
6.7
7.0
6.7
6.3
6.7
6.0
6.3
6.7
6.3

June
7.0
7.0
7.0
7.0
7.0
7.3
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
6.7
7.3
7.0
7.0
7.0
7.0
6.7
7.0
7.0
7.0
7.0
6.7
7.0
7.0
6.7
7.0
7.0
7.0
*7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.3
7.0
7.3
6.7
7.0
6.7
6.3
6.7
6.7

8

July

Aug

Sept

Oct

Mean

6.7
6.7
6.7
6.7
7.0
7.3
7.0
7.0
7.0
7.0
6.7
7.0
7.0
7.3
7.0
7.0
6.7
7.3
7.3
7.0
7.7
7.3
7.0
6.7
7.0
7.0
7.0
7.0
7.0
6.7
7.0
7.0
7.3
6.7
6.7
6.3
7.0
7.0
6.7
7.3
7.3
7.0
6.7
7.0
7.0
7.0
7.3
7.0
7.0
7.3
7.0
7.0
6.3
7.0
6.3

7.7
7.3
7.7
8.0
7.3
7.3
7.3
7.3
7.3
7.3
7.3
7.0
7.7
7.0
7.3
7.3
7.3
7.0
7.0
7.7
7.0
7.0
7.3
7.3
7.3
7.3
7.3
7.7
7.0
7.3
7.3
7.7
7.0
7.3
6.7
7.3
7.3
7.3
7.3
7.0
7.3
6.7
6.7
6.3
6.7
6.3
6.7
7.0
7.0
6.7
7.0
6.7
7.3
6.3
6.3

7.0
7.0
7.0
7.0
7.0
7.0
7.0
6.7
7.3
7.0
7.0
7.0
7.0
6.7
7.0
6.7
7.0
6.7
6.7
6.7
6.7
7.0
6.7
7.7
7.0
7.0
7.0
6.3
7.0
7.3
7.0
6.7
6.7
6.3
7.0
6.7
7.0
6.7
7.0
6.7
6.7
6.7
7.3
7.0
6.7
7.0
6.7
6.3
6.3
6.7
6.3
6.7
6.0
5.7
6.0

6.7
7.0
6.7
6.7
6.7
6.7
6.7
7.0
6.7
7.0
6.7
6.7
6.0
6.7
6.7
6.3
6.3
6.7
6.3
6.0
6.0
7.0
6.3
7.0
6.0
6.3
6.3
6.3
7.0
6.3
6.3
6.7
6.0
6.3
6.7
6.7
6.0
6.3
6.0
6.7
5.7
6.3
6.3
7.0
6.0
6.7
5.7
5.3
5.3
6.0
5.3
5.7
5.3
5.0
5.0

7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.9
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.7
6.7
6.7
6.7
6.7
6.7
6.6
6.6
6.6
6.6
6.4
6.3
6.2
6.1

124
125

Cultivar

May

June

July

Aug

Sept

Oct

Mean

Kenblue
Ginger
l s d (005)

6.0
5.3
0.9

6.0
5.7
0.6

5.7
5.3
0.8

7.0
6.3
1.3

5.3
5.7
1.0

5.0
4.7
1.0

5.8
5.5
0.4

Quality based on a scale of 9 to 1: 9 = best quality, 6 = lowest acceptable quality, and 1 = poorest quality.

Table 2. The 1994 quality ratings for the high-maintenance, non-irrigated regional Kentucky bluegrass test.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45

Cultivar

May

June

July

Monopoly
Mystic
BA 72-500
NE 80-50
Sydsport
Blacksburg
NE 80-14
Cheri
Wabash
Asset
A-34
Midnight
NE 80-30
BA 70-139
BA 73-540
Somerset
BA 72-441
America
Compact
Haga
Georgetown
BA 70-242
BA 69-82
Merion
Aquila
Aspen
NE 80-48
Classic
P-104
BA 73-626
HV 97
Lofts 1757
Eclipse
Dawn
Amazon
Julia
PST-CB1
Ram I
Parade
Nassau
Huntsville
F-1872
NE 80-55
Conni
NE 80-88

7.3
6.7
7.3
7.3
7.3
7.3
7.0
7.3
7.0
6.7
7.0
6.3
6.3
8.0
7.7
6.3
5.3
7.3
7.0
6.7
6.3
6.7
7.0
6.7
5.7
6.3
6.7
6.7
6.0
6.7
6.7
6.3
6.0
6.7
6.3
6.7
6.7
6.7
6.0
6.7
5.7
5.7
6.0
6.0
6.0

7.3
8.7
8.0
7.7
8.3
7.7
7.7
7.7
7.7
7.7
8.0
7.3
6.7
7.0
7.7
7.0
6.3
6.7
7.3
7.0
6.3
6.7
6.7
6.7
6.3

7.3
8.0
7.3
6.7
7.0
7.0
6.7
6.3
7.0
7.3
6.7
6.7
7.0
5.7
6.3
7.0
6.7
6.7
6.7
5.7
6.7
6.7
6.3
6.3
6.7
6.3
6.3
6.3
6.7
5.7
6.3
6.7
6.0
5.7
6.0
6.7
6.0
5.7
6.0
6.3
6.3
5.7
6.7
6.3
6.0

,

67
7.0
6.7
6.3
6.0
6.3
6.3
6.7
6.3
7.0
5.3
6.7
7.3
6.3
6.7
6.0
6.7
6.7
6.3
6.3

9

Aug
6.7
6.0
5.7
.6.3
5.3
6.3
6.3
5.7
5.7
6.0
5.3
5.7
6.0
4.7
6.0
5.0
5.7
5.7
5.0
6.0
6.3
5.7
5.3
5.7
6.3
5.3
5.3
5.0
6.3
6.3
5.3
6.0
5.7
5.7
6.0
5.7
5.0
5.7
6.3
5.7
6.0
5.3
5.7
5.7
6.0

Sept

Oct

Mei

7.3
6.0
7.0
7.3
7.0
7.0
6.7
6.7
7.3
6.7
6.0
6.3
6.7
7.3
5.7
7.0
7.3
6.3
6.3
6.3
6.3
6.0
6.0
6.0
6.3
6.3
6.0
6.0
6.0
6.0
7.0
6.7
6.7
6.7
6.0
6.7
6.3
5.3
6.3
6.0
5.7
6.7
6.0
6.3
5.7

6.7
7.3
7.3
7.0
6.7
6.3
7.3
7.0
6.3
6.0
6.7
7.0
7.0
6.3
5.7
6.3
7.0
6.0
5.3
6.0
6.0
6.0
6.7
6.7
6.3
6.7
6.3
6.3
5.7
6.3
5.7
5.3
6.3
6.0
5.7
6.3
6.3
6.0
5.7
5.3
6.7
6.7
5.3
5.3
6.0

7.1
7.1
7.1
7.1
6.9
6.9
6.9
6.8
6.8
6.7
6.6
6.6
6.6
6.5
6.5
6.4
6.4
6.4
6.3
6.3
6.3
6.3
6.3
6.3
6.3
6.3
6.3
6.2
6.2
6.2
6.2
6.2
6.2
6.2
6.2
6.2
6.2
6.1
6.1
6.1
6.1
6.1
6.1
6.0
6.0

46 .
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80

Cultivar

May

WW AG 491
WW AG 495
NE 80-47
Able I
Cynthia
Glade
Rugby
K3-178
Barzan
BA 72-492
Kl-152
Trenton
Challenger
Gnome
Merit
BAR VB 577
BAR VB 534
Liberty
Ikone
NE 80-110
Tendos
Destiny
Park
Victa
WW AG 496
Joy
Baron
Annika
Bristol
239
Harmony
WW AG 468
Kenblue
Welcome
South Dakota Cert.
l s d (005)

6.7
6.3
5.7
6.7
6.0
5.7
5.7
6.7
6.3
6.7
6.3
6.3
6.0
5.7
6.0
5.3
5.7
5.0
6.0
6.7
5.7
5.7
5.0
6.0
6.3
4.7
5.7
5.7
5.7
5.3
5.7
5.0
4.3
5.3
4.7
1.4

June
7.0
6.7
6.0
6.3
6.0
6.7
6.3
5.7
6.0
6.0
6.0
6.3
6.7
5.7
6.0
6.0
6.0
6.0
6.0
6.7
5.3
6.0
6.0
6.3
6.0
5.3
5.0
6.7
6.3
5.7
6.0
5.3
5.0
5.3
5.0
•V 1.4

July

Aug

Sept

Oct

Mean

5.7
6.3
6.3
5.7
6.3
5.3
6.0
6.3
6.0
5.7
5.7
6.0
5.7
6.3
6.3
6.0
5.7
6.0
5.7
6.0
5.0
5.7
5.7
5.0
5.3
5.3
5.0
5.3
5.3
5.3
5.7
5.7
5.3
5.3
5.0
1.3

5.3
6.0
5.7
5.7
5.3
6.0
5.7
5.7
5.3
5.0
5.3
5.3
5.0
5.3
5.0
4.7
5.7
5.3
5.0
4.3
5.7
5.3
6.0
5.0
5.0
6.0
5.7
5.0
4.7
5.0
5.0
5.0
5.7
4.7
5.3
1.3

5.7
5.0
6.3
6.0
6.3
5.7
6.3
5.3
5.3
5.7
6.0
5.7
5.7
5.7
5.7
6.3
5.7
5.7
6.0
5.7
6.3
5.7
5.7
5.3
5.3
6.3
6.0
5.3
5.3
5.7
5.3
5.3
6.0
5.0
5.0
1.6

5.7
5.7
6.0
5.3
5.7
6.0
5.7
5.7
6.0
6.0
5.3
5.3
5.7
5.7
5.3
6.0
5.7
6.0
5.7
4.7
5.7
5.3
5.3
5.3
5.0
5.0
5.3
4.7
5.3
5.3
5.0
5.3
4.7
5.0
4.7
1.5

6.0
6.0
6.0
5.9
5.9
5.9
5.9
5.9
5.8
5.8
5.8
5.8
5.8
5.7
5.7
5.7
5.7
5.7
5.7
5.7
5.6
5.6
5.6
5.5
5.5
5.4
5.4
5.4
5.4
5.4
5.4
5.3
5.2
5.1
4.9
0.9

Quality based on a scale of 9 to 1: 9 = best quality, 6 = lowest acceptable quality, and 1 = poorest quality.

Table 3. The 1994 quality ratings for the low-maintenance, non-irrigated Kentucky bluegrass trial.

1
2
3
4
5
6
7
8
9
10
11
12

Cultivar

May

June

July

Aug

Sept

Oct

Mean

BAR VB 852
Bronco
ISI-21
Monopoly
GEN-RSP
PST-YQ
PST-C-391
Barm ax (BAR VB 7037)
Baron
Baronie (BAR VB 985)
Nublue (J-229)
Suffolk

7.0
6.3
6.0
6.7
7.7
7.3
6.0
5.7
4.7
6.3
6.0
6.0

7.3
6.3
6.0
6.3
6.3
6.3
6.3
6.3
6.3
5.3
6.7
5.7

6.7
6.7
6.7
6.0
6.0
6.3
5.7
5.7
5.3
5.7
6.0
6.0

5.7
5.0
5.0
5.0
4.3
5.0
5.7
5.0
5.3
5.3
4.7
5.0

5.7
5.7
6.0
6.0
5.3
5.0
5.7
6.0
5.7
5.7
4.7
5.0

6.0
6.7
6.3
6.0
6.0
5.7
5.7
5.3
7.0
5.0
5.7
6.0

6.4
6.1
6.0
6.0
5.9
5.9
5.8
5.7
5.7
5.6
5.6
5.6

10

Cultivar
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62

BA 78-376
Banjo (H76-1034)
Minnfine (MN 2405)
Park
South Dakota Cert.
Caliber (J-335)
Destiny
Freedom
Liberty
PST-C-303
Voyager
Barcelona (BAR VB 118)
Barzan
Merit
PST-A7-111
Ram-1
Alene
* Cynthia
EVB 13.863
Gnome
Haga
Livingston
Midnight
Miracle
Sophia
Washington
NE 80-47
Amazon
Belmont (798)
Chelsea
Cobalt
EVB 13.703
ZPS-84-749
BA 74-017
J-386
Kyosti
Njic
Nustar
Unique (PST-C-76)
BAR VB 1169
Crest
Kenblue
Merion
Opal
SR 2000
KWS PP 13-2
Barsweet
Bartitia
Fortuna
Unknown
LSDmo5)

May
5.3
6.0
4.3
6.0
6.3
5.7
5.3
6.3
5.3
5.0
7.0
5.3
5.3
5.0
5.0
5.0
5.7
5.0
5.0
5.3
5.7
5.7
5.3
5.7
5.3
5.3
5.7
5.3
6.0
5.7
5.0
6.0
5.3
5.0
5.3
5.3
6.3
4.7
5.7
5.7
5.0
4.3
5.3
5.7
5.0
5.7
5.3
4.3
4.7
4.7
1.4

June
5.3
5.0
6.0
5.7
5.3
6.0
5.7
6.0
6.0
5.7
6.0
5.7
4.7
5.7
5.7
5.0
5.7
6.0
6.0
5.7
5.3
5.7
6.3
6.3
5.7
5.3
5.7
5.3
5.7
5.0
5.3
5.7
5.3
5.7
5.3
v 6.0
5.0
5.0
5.7
5.3
5.3
5.0
5.3
6.0
5.3
5.0
5.3
5.0
6.0
5.0
4.6

July

Aug

Sept

Oct

Mean

5.3
5.7
6.3
5.0
6.0
5.3
5.3
5.3
5.7
6.0
5.3
5.3
6.0
5.3
5.7
5.3
5.0
4.7
5.7
5.7
5.7
5.0
6.0
5.0
5.0
5.3
5.0
5.0
5.3
4.7
5.7
5.3
5.0
5.0
5.0
5.0
5.0
5.3
5.3
5.3
4.7
5.0
4.7
5.0
4.0
4.7
5.3
5.0
4.0
4.0
2.3

5.0
4.7
4.3
4.0
5.0
4.7
4.3
4.7
4.3
4.3
4.3
4.3
4.7
5.0
4.0
4.7
4.0
4.7
5.0
4.3
4.3
4.7
4.0
3.3
4.7
3.7
3.7
4.7
4.3
4.0
3.7
3.7
4.3
4.0
4.3
4.0
3.3
4.0
3.7
3.7
3.7
3.7
3.7
3.3
4.0
4.0
3.3
3.7
3.7
3.3
4.6

6.3
5.7
5.3
5.7
5.0
5.0
5.0
5.0
5.3
5.0
4.0
5.0
5.3
4.7 .
5.3
5.0
5.0
5.0
4.3
4.7
5.0
4.3
3.7
4.7
4.7
5.3
5.0
4.0
4.0
4.7
4.7
3.7
4.7
4.0
3.7
4.0
4.3
4.7
3.7
3.3
3.7
4.7
4.3
3.7
4.3
4.0
3.7
4.0
3.3
2.7
2.8

5.7
5.3
6.0
6.0
5.0
5.0
6.0
4.7
5.3
5.7
5.3
5.7
5.0
5.3
5.3
6.0
5.3
5.3
4.7
5.0
4.3
5.0
5.0
5.3
5.0
5.3
5.0
5.0
4.3
5.7
5.0
5.0
4.7
5.0
5.0
4.3
4.7
5.3
4.3
4.0
5.0
4.7
4.0
4.0
5.0
3.7
3.3
4.0
3.7
3.7
3.5

5.5
5.4
5.4
5.4
5.4
5.3
5.3
5.3
5.3
5.3
5.3
5.2
5.2
5.2
5.2
5.2
5.1
5.1
5.1
5.1
5.1
5.1
5.1
5.1
5.1
5.1
5.0
4.9
4.9
4.9
4.9
4.9
4.9
4.8
4.8
4.8
4.8
4.8
4.7
4.6
4.6
4.6
4.6
4.6
4.6
4.5
4.4
4.3
4.2
3.9
2.0

Quality based on a scale of 9 to 1: 9 = best quality, 6 = lowest acceptable quality, and 1 = poorest quality.

11

Recovery of Kentucky Bluegrass Cultivars
Following Summer Dormancy -1994
N. E. Christians
In earlier work at Iowa State University (Grounds Maintenance 24(8):49-50) it was shown that Kentucky
bluegrass cultivars vary greatly in their recovery from summer dormancy. Common, or public varieties,
generally recover much more rapidly from drought-induced dormancy than do the newer improved
cultivars. The objectives of this study are to further evaluate four cultivars that were previously shown to
recover rapidly from dormancy and four cultivars that were slower to recover when maintained under
low and high fertility regimes: 1 lb N/1000 fit2 in September and 4 lb N/1000 ft2 applied in 1 lb
applications in April, May, August, and September.
South Dakota Common, S-21, Kenblue, and Argyle (cultivars observed to recover rapidly in earlier
studies) and Midnight, Nassau, Glade, and Ram I (cultivars observed to recover more slowly). Kentucky
bluegrass was established in 21 fit2 plots on September 26, 1989 on a non-irrigated site at the turfgrass
research area of the Iowa State University Horticulture Research Station north of Ames, Iowa. The soil
on the site is a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with a pH of 6.8 and 2.3% organic
matter, a P content of 20 lbs/A. and a K content of 216 lbs/A. The study was replicated three times.
Each plot was split in half. The two fertility treatments were randomly applied to the two halves of the
plots.
The 1990 season was very wet and at no time did the grasses on the study area go into summer
dormancy. The spring of 1991 was also very wet and the late summer and fall were dry. The 1992
season was the opposite of the 1991 season. The spring and summer were very dry up to the 4th of July.
The remainder of the summer and fall were very wet. The 1993 season was one of the wettest in history.
The area remained saturated through most of the season. At no time was there any moisture stress. The
1994 season was moderate, with some slight moisture stress in late summer.
Data were collected in July, August, and September 1994 (Table 4). The improved varieties had
deteriorated in quality during the drier years of 1990, 1991, and 1992, but recovered well in the wet
conditions of 1993. In 1994, the performance of common and improved varieties was very similar,
which would be expected in the moderate conditions experienced during the season.
Table 4. The 1994 quality ratings for the low-moderate maintenance bluegrass study.
July
Cultivar

1 lb
N

4 1b
N

S.D. Common

6.3

6.0

S-21

5.3

7.0

Kenblue

5.0

6.3

Argyle

5.7

6.3

Midnight

5.0

7.0

Nassau

4.0

4.3

Glade

6.3

6.0

RAM-I

5.3

6.7

LSD(oo5)

i
!

.91

i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
11
i
i
i
i
i
i
i
i
i
i
i

12

August
1 lb
N

4 1b
N

5.6

6.3

5.3

6.3

5.7

5.7

5.3

5.7

4.3

6.0

4.3

5.0

6.3

6.0

5.0

5.0
1.03

i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i

September
1 lb
N

4 lb
N

5.3

6.0

5.3

5.7

4.0

5.3

5.0

5.3

4.3

6.0

4.0

5.0

5.3

6.3

4.7

4.7
1.78

National Perennial Ryegrass Study - 1994
J. D. Dickson and N. E. Christians
This trial began in the fall of 1990 with the establishment of 125 cultivars of perennial ryegrass at the
Iowa State University Horticulture Research Station. The study was established on an irrigated area that
was maintained at a 2-inch mowing height and fertilized with 3 to 4 lb N/1000 fit2/yr. The area receives
preemergence herbicide in the spring and was treated with a broadleaf herbicide in September of 1993.
The trial was terminated following data collection in August of 1994 and was replaced by a new ryegrass
trial.
Cultivars were evaluated for turf quality each month of the growing season. Visual quality was based on
a scale of 9 to 1: 9 = best quality, 6 = lowest acceptable quality, and 1 = poorest quality. The values
listed under each month in Table 5 are the averages of ratings made on three replicated plots for the three
studies. Yearly means of data from each month are listed in the last column. The cultivars are listed in
descending order of average quality.
Winter kill of the ryegrasses was particularly severe in the spring of 1993. There was much less winter
damage in the spring of 1994 and most cultivars showed no winter kill by the May rating. Few of the
standard perennial ryegrass varieties used in Iowa ranked near the top, indicating that there are a number
of new cultivars coming along in the next few years that should be well adapted to conditions here (Table

5).
Table 5. The 1994 quality ratings for the national perennial ryegrass study established in 1990.

1
2
3
4
5
6
7
8
9
10
11
12
13
14

Cultivar

May

June

July

Aug

Mean

HE 311
Charger
Pick EEC
PR 9119
C-21

7.3
7.0
7.3
6.7
7.0

7.7
7.7
7.0
7.3
7.0

7.7
7.7

7.7
7.7

7.3
7.7

7.3
7.7

7.3

Cutless
Dandy

7.3
7.3

7.3

7.3
7.0

7.6
7.5
7.3
7.3
7.2

Delaware Dwarf (4DD)
Affinity (GEN-90)

7.3
7.0

Barrage ++
Cutter (Pick 89-4)

7.0
7.3
7.0
7.0

Elite (WVPB-88-PR-C-23)
Lindsay
Loretta
SR 4200
Stallion Select (PS-105)

7.0
7.0
7.0

WVPB 89-92
Assure
Derby Supreme

7.3
7.0

Express

7.0

25

Pronto (WVPB-89-87A)
PST-20G
PST-2ROR
Shining Star (PST-2B3)
APM

26
27

Buccaneer (KOOS 90-1)
Fiesta II

15
16
17
18
19
20
21
22
23
24

7.3
7.3
7.3
7.3 '
7.0
7.3
7.3
7.3
7.3
7.3

7.0

7.3
6.7

7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0

7.0

7.0

7.0
7.0

7.0
7.0
7.0

7.0
7.0
7.0

7.0
7.0
7.0
6.7
7.3

7.0
7.0
7.3
7.0
7.0

7.0
7.0
6.7
7.0
6.7

13

7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
6.7
7.0
6.7

7.2
7.2
7.2
7.1
7.1
7.1
7.1
7.1
7.1
7.1
7.1
7.1
7.0
7.0
7.0
7.0
7.0
7.0
7.0
6.9
6.9
6.9

28
29
30
31
32
33
34
35
36
37
38
39
40
41

Cultivar

May

June

July

Aug

Mean

Gator
Gettysburg
MVF 89-88

7.3
7.0

7.0
7.3

6.7
6.7

6.7

7.3
7.0

7.0
6.7

6.7

6.9
6.9
6.9

7.3
7.3
6.7
7.0
7.0
7.0
7.0
7.0
7.0

7.0
7.0
7.0
6.7

PR 9118
PST-290
Riviera II (Pick DKM)
Rodeo II
89-666
Achiever (Pick 1800)
Barrage
Citation II
CLP 144
Commander

42

Cowboy II (WM-II)
Danaro

43
44

Dimension (2H7)
Entrar

45
46
47
48
49
50
51
52

Equal
Greenland (Pick 9100)
KOOS 90-2
Lowgrow (Pick 89LLG)
Manhattan II (E)
Navajo (PST-2DPR)
Pennfine
Pleasure
Prelude II (2P2-90)

7.0
7.3
7.0
7.0
7.0

7.0
6.3
7.0
7.0
6.7
6.7
7.0
7.0
7.0

7.0
6.7
7.0
6.7
7.0
6.7
7.0
7.0
7.0
7.0
7.0
7.0
7.3

7.0
6.7
6.7
7.0
6.7
6.7
6.3
6.7
6.7
6.7
6.7
7.0
6.7
6.7
6.7
7.0
6.7
6.7
6.7
6.7
6.7
7.0

55
56
57
58

PS 89-90 (MVF 89-90)
PST-28M
Repell II (LDRD)
Riviera
Sherwood

7.0
6.7
6.3
7.3
7.0
7.0
6.3
7.0
7.0

7.0
7.0
7.0
7.0
7.0

7.0
6.7
6.7

59
60
61

Statesman (WVPB-88-PR-D-12)
Target
Taya

7.0
7.0
7.0

7.0
7.0
7.0

6.7
6.7
6.7

62
63
64
65
66
67

Toronto
Unknown
Yorktown III (LDRF)
Advent
BAR LP 086FL
BAR LP 852

•v 7.0
7.0
6.7
7.0

6.3
6.7
7.0
6.3
6.7
6.3

68
69

Calypso
Capri (ZW 42-176)
Competitor
Danilo
Duet
Evening Shade (Poly-Sh)
N-33

7.3
7.0
6.7
7.0
7.0
7.0
7.0
6.7
7.0
7.3
7.0
6.7

53
54

70
71
72
73
74
75
76

Nighthawk (WVPB-89-PR-A-3)
Ovation

77

Patriot II

78
79

Precision (MOM LP3147)
PST-23C
PST-2FF

80

6.3
7.0
7.0
6.7
7.0
6.7
7.0
6.7
7.0
7.0
6.3
7.0
7.0
6.7
6.7

14

6.3
6.7
6.7

6.7
6.7
7.0
6.7
6.7
7.0
6.7
6.7
6.3
6.7
6.7
6.7
6.7
7.0
6.7
6.7
6.7
7.0
6.7
6.7
6.7
6.7
6.7
7.0
6.3
6.7
6.7
7.0
6.7

6.9
6.9
6.9
6.9
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8

6.7
6.7
6.7
6.7

6.8
6.8
6.8

6.3
6.7
7.0
6.3
6.7

6.8
6.8
6.8
6.7
6.7

6.3
6.7

6.3
6.3
6.7

6.3
6.3
6.3
6.7

6.3
6.3
6.3
6.7

6.7
6.7
6.7
6.7

7.0
7.0
7.0

6.3
6.3
6.7

6.3
6.3
6.7

6.7
6.7

7.0
7.0
6.7
6.7

6.3
6.3
6.7

6.3
6.3
6.7

6.7
6.7

6.7

6.7

6.7

6.7
6.7
6.7
6.7

6.7

Cultivar

May

June

July

Aug

Mean

81
82

Quickstart (PST-2FQR)
Seville

7.0
6.7

Troubadour
CLP 39

6.3

6.3
6.7
6.7

6.3
6.7

83

7.0
6.7
7.0

6.7

6.7

7.0

6.3

6.3

6.7
6.7
6.7
6.6

6.7
6.7

7.0
7.0
7.0
7.0

6.3
6.3
6.3
6.3
6.3

6.3
6.3
6.3
6.3
6.3
6.3
6.0
6.0

84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102

Envy
Morning Star (Syn-P)
OFI-D4

6.7
6.7

Pinnacle
Premier
Stallion
Allegro
Essence (PR 8820)
Nomad

6.7
6.7
7.0

PR 9108
Repell
Topeka (WVPB-88-PR-D-10)
240 (Pebble Beach)
EEG 358
MOM LP 3184

6.6
6.6
6.6
6.6
6.6

7.3
7.0
7.0
7.0

7.0
7.0
7.0
6.7
7.0

6.3
6.0
6.0
6.0

7.0
6.3

6.0
6.3

6.0
6.0
6.3

6.5
6.5

7.0
6.7

7.0
7.0

6.0
6.0

6.0
6.0

6.5
6.4

6.0
6.3
6.7
7.0
6.3
6.7

7.0
6.7

6.3

6.3
6.3
6.0
6.0
6.3
6.0
6.3

6.4
6.4
6.4
6.4

6.6
6.5
6.5
6.5

103
104

Mulligan (NK 89001)
Pennant
PR 9121
Prizm (ZPS-28D)
Saturn

105

Brightstar (PST-GH-89)

6.3
6.3 .

6.7

6.3
6.0
6.0
6.3
6.0
6.3
6.0

106
107

Cartel

6.3

6.3

6.3

Legacy

7.0

7.0

5.7

5.7

6.3

108
109
110
111
112
113
114

Palmer II (P89)
PR 9109
ZPS-2EZ
Accolade

6.7
6.7
7.0
6.0
6.7
7.0
7.0

6.0
6.7
6.3
6.7
6.7
6.3
6.3
6.7

6.3
6.0
6.0
6.0

6.3
6.0
6.0
6.0
5.7
5.7

6.0

6.3
6.3
6.3
6.2
6.2
6.2
6.2
6.2

7.0
7.0

6.0
5.7

6.3
6.0

115
116
117

Caliente
Goalie
MOM LP 3111
MOM LP 3185
Surprise
Meteor

118
119

MOM LP 3182
OFI-F7

6.3
6.7

120

Regal

6.0

121
122

856
MOM LP 3179
Linn

6.0
6.0
5.0

LSD(005)

1.0

123

>

6.0
5.7
6.0

7.0
6.7
6.7
7.0
6.7

5.7
5.7
5.7

6.4
6.4
6.4

6.0

6.3

6.3

6.3

5.7
6.0
6.0

6.2
6.1

5.7
5.7

5.7
5.7
5.7

6.0
6.0

6.7

5.7

5.7

6.0

6.0
5.7

5.3
5.0
3.0

5.3
5.0
3.3
1.6

5.7
5.4

4.3
0.9

1.5

3.9
0.8

Quality based on a scale of 9 to 1: 9 = best quality, 6 = lowest acceptable quality, and 1 = poorest quality.

15

Regional Fine Fescue Cultivar Evaluation - 1994
J. D. Dickson and N. E. Christians
This was the first full year of data from the new fine fescue trial. This is a National Turfgrass Evaluation
Program (NTEP) trial. It is being conducted at many locations around the U.S. The purpose of the trial
is to study the regional adaptation of 59 fine fescue cultivars. Cultivars were evaluated for quality each
month of the growing season through October. The study is established in full sun. Three replications of
the 59, 3 ft x 5 ft (15 ft2) plots were established in September of 1993. The trial is maintained at a 2-inch
mowing height, 3 to 4 lb N/1000 ft2 were applied during the growing season, and the area was irrigated
when needed to prevent drought. Preemergence herbicide was applied once in the spring.
Visual quality was based on a scale of 9 to 1: 9 = best quality, 6 = lowest acceptable quality, and 1 =
poorest quality. Dawson received the highest rating in 1994.
Table 6. The 1994 quality ratings for the fine fescue regional cultivar trial

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36

Cultivar

Species

May

June

July

Aug

Sept

Oct

Mean

Dawson
Pick 4-91W
PST-44D
PST-4VB Endo.
Rondo
SR 5100
Jasper (E)
Aruba
MB 61-93
Shademaster II
WX3-FFG6
Medina
NJ F-93
PST-4DT
WX3-FF54
Jamestown II
PRO 92/20
PST-4ST
TMI-3CE
Seabreeze
ZPS-4BN
Banner II
MB 63-93
MB 64-93
Treazure (ZPS-MG)
Common Creeping
Jamestown
MB 65-93
MB 66-93
Cascade
Shadow (E)
WVPB-STCR-101
BAR Frr 4ZBD
Brittany
CAS-FR13
Discovery

SLC
CF
CF
STC
STC
CF
STC
STC
CF
STC
STC
CF
CF
STC
CF
CF
CF
STC
CF
SLC
STC
CF
CF
CF
CF
STC
CF
CF
CF
CF
CF
STC
STC
CF
STC
HF

6.7
6.0
6.0
5.7
6.3
6.0
6.3
6.7
5.3
6.3
6.3
6.0
6.0
6.0
5.7
6.3
6.0
6.0
6.3
5.7
6.0
6.0
5.3
5.7
5.7
6.7
6.7
5.3
5.7
7.0
5.7
6.0
5.7
5.3
6.3
6.0

7.3
7.7
7.0
6.3
7.3
7.7
7.0
6.7
6.7
7.3
7.0
7.0
7.3
6.7
7.0
7.0
7.3
V
7.0
7.0
6.7
6.3
7.0
6.7
6.7
6.3
5.7
7.0
7.0
6.3
6.7
6.7
6.0
6.0
6.3
5.7
6.7

7.3
5.7
7.0
6.7
6.7
5.3
6.3
6.0
6.0
6.7
6.3
5.7
5.7
5.3
6.0
5.3
6.3
6.3
6.0
6.3
5.7
5.3
6.3
5.7
5.7
5.0
5.7
5.7
5.7
5.7
5.7
6.0
6.0
6.0
5.7
7.0

5.3
6.0
6.0
6.3
6.7
6.0
5.3
6.0
5.7
5.0
5.0
5.3
5.0
5.3
5.3
5.3
4.3
4.0
4.0
4.7
5.0
4.3
5.0
5.0
6.0
5.7
4.3
5.0
4.7
4.3
4.7
5.3
5.0
4.7
4.3
3.0

7.0
7.3
7.0
7.7
6.3
7.0
7.0
6.7
7.7
6.3
7.0
6.3
6.7
6.7
6.7
6.3
6.0
7.0
7.0
6.7
6.3
6.0
6.0
6.0
6.0
6.0
5.3
5.7
7.0
5.3
6.3
5.3
5.3
5.7
5.3
5.3

6.0
7.0
6.7
6.7
6.0
7.0
6.7
6.0
6.7
6.0
6.3
6.7
6.3
7.0
6.3
6.3
6.3
6.3
6.3
6.0
6.7
6.7
6.0
6.7
6.0
6.0
6.0
6.0
5.7
5.3
5.3
5.3
5.7
5.3
6.3
5.3

6.6
6.6
6.6
6.6
6.6
6.5
6.4
6.3
6.3
6.3
6.3
6.2
6.2
6.2
6.2
6.1
6.1
6.1
6.1
6.0
6.0
5.9
5.9
5.9
5.9
5.8
5.8
5.8
5.8
5.7
5.7
5.7
5.6
5.6
5.6
5.6

16

37.
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59

Cultivar

Species

Darwin
PRO 92/24
Reliant II
BAR UR 204
ISI-FC-62
Victory (E)
SR 3100
Tiffany
Bridgeport
MB 82-93
Molinda
Brigade
Ecostar
Flyer
Quatro (FO 143)
Spartan
Scaldis
MB 81-93
Nordic
Aurora w/endo.
MB 83-93
Pamela
67135
l s d (005)

CF
HF
HF
STC
CF
CF
HF
CF
CF
HF
CF
HF
HF
STC
SF
HF
HF
HF
HF
HF
HF
HF
SF
—

May

June

July

Aug

Sept

Oct

Mean

5.0
6.0
5.7
6.0
5.3
5.3
6.3
5.7
5.3
5.7
5.3
6.3
6.0
6.0
6.3
6.3
5.7
6.0
5.7
5.0
5.7
5.0
5.0
1.4

6.3
7.3
7.3
6.0
6.7
6.3
7.7
6.7
6.3
6.7
5.7
7.0
6.7
6.0
6.7
6.7
6.7
7.0
6.7
6.3
6.7
6.0
4.0
0.9

6.7
6.0
6.0
5.0
6.0
5.7
5.7
5.0
5.3
5.0
5.3
4.3
4.3
4.7
4.0
4.3
4.7
4.3
3.7
4.0
4.0
4.0
1.3
1.4

4.0
2.7
2.7
4.0
3.3
3.3
2.0
3.7
4.3
2.7
4.7
2.3
2.3
3.3
3.3
2.3
2.7
2.3
2.3
2.7
2.0
2.3
1.7
1.6

6.0
5.7
6.0
6.0
5.7
6.0
5.3
5.7
5.0
5.3
5.0
4.3
4.7
4.3
5.0
5.0
4.7
4.3
5.0
5.0
4.7
4.0
2.7
2.1

5.0
5.3
5.3
5.7
5.3
5.7
5.0
5.3
4.7
4.7
4.0
4.7
4.7
4.3
3.3
4.0
3.7
3.7
4.0
4.0
4.0
3.7
2.7
1.6

5.5
5.5
5.5
5.4
5.4
5.4
5.3
5.3
5.2
5.0
5.0
4.8
4.8
4.8
4.8
4.8
4.7
4.6
4.6
4.5
4.5
4.2
2.9
1.0

Quality based on a scale of 9 to 1: 9 = best quality, 6 = lowest acceptable quality, and 1 = poorest quality.
CF = Chewings Fescue
HF = Hard Fescue
SF = Sheep Fescue
SLC = Slender Creeping Fescue
STC = Strong Creeping Fescue

17

Shade Adaptation Study -1994
N. E. Christians

A shade adaptation study was established in the fall of 1987 to evaluate the performance of 35 species
and cultivars of grasses. The species include creeping red fescue (C.R.F.), hard fescue (H.F.), tall
fescue (T.F.), Kentucky bluegrass (K.B.), and rough bluegrass
trivialis).
The area was located under the canopy of a mature stand of Siberian elm trees (
pumila) at the
Iowa State University Horticulture Research Station north of Ames, Iowa. Grasses were mowed at a
2-inch height and received 2 lb N/1000 ft2/year. No weed control has been required on the area, but
turf was irrigated during extended droughts.
Monthly quality data were collected from May through October (Table 7). Visual quality was based on
a scale of 9 to 1: 9 = best quality, 6 = lowest acceptable quality, and 1 = poorest quality. This trial
has been observed through the extremes of the drought year 1988 and the very wet conditions of 1993.
Turf quality among species varied greatly with moisture conditions. In dry weather, the fine fescues,
especially the hard fescues, do well, whereas rough bluegrass {Poa trivialis) quickly deteriorates. In
extended wet periods, rough bluegrass does very well. Some of the tall fescues and chewings fescues
also tend to perform better in wet conditions.
The 1994 season was neither too wet, nor too dry. Growing conditions were nearly ideal through most
of the year. The chewings fescues were among the highest rated cultivars in 1994. Tall fescue also
performed well. Kentucky bluegrass did not perform well in 1994 and most bluegrass varieties were
near the bottom of the list.
A new shade trial was added in the fall of 1994 and will be reported on in next year’s report. The
older shade trial will also be maintained for a few more seasons.

Table 7. 1994- quality ratings for grasses in the 1987 shade trial.
Cultivar
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17

Victor (C.F.)
Jamestown (C.F.)
Shadow (C.F.)
Mary (C.F.)
Falcon (T.F.)
Waldorf (C.F.)
Sabre (Poa trivialis)
Rebel II (T.F.)
Bonanza (T.F.)
Estica (C.R.F.)
ST-2 (SR 3000) (H.F.)
BAR FO 81-225 (H.F.)
Rebel (T.F.)
Waldina (H.F.)
Koket (C.F.)
Atlanta (C.F.)
Banner (C.F.)

May
7.3
7.7
7.0
6.7
6.7
5.3
7.7
6.7
6.3
5.3
' 5.7
5.0
6.7
5.3
6.0
5.0
6.0

June

July

Aug

Sept

Oct

Mean

7.7
7.0
7.0
7.0
6.7
7.3
7.3
6.3
6.3
6.0
6.0
6.0
6.3
6.0
5.7
7.0
6.0

6.7
5.7
5.7
6.3
5.0
5.7
5.7
5.0
5.7
6.3
5.7
5.3
4.3
5.0
4.7
4.7
4.3

6.7
6.0
6.3
6.0
5.7
6.0
4.3
6.0
5.7
6.0
6.3
5.7
5.7
5.3
6.3
5.7
5.3

7.0
7.0
6.7
6.7
7.0
6.0
6.0
7.0
6.7
6.3
6.3
7.3
6.7
6.0
6.0
6.3
6.0

7.3
6.3
6.7
7.0
6.7
7.0
6.0
6.3
6.3
6.7
6.3
7.0
6.0
7.0
5.7
5.3
6.0

7.1
6.6
6.6
6.6
6.3
6.2
6.2
6.2
6.2
6.1
6.1
6.1
5.9
5.8
5.7
5.7
5.6

18

Cultivar
18
19
20
21
22
23
24
25
26
27 .
28
29
30
31
32
33
34
35

Aridf (T.F.)
Pennlawn (C.R.F.)
Ensylva (C.R.F.)
Apache (T.F.)
Agram (C.F.)
Biljart (H.F.)
Spartan (H.F.)
Wintergreen (C.F.)
Reliant (H.F.)
Highlight (C.F.)
Coventry (K.B.)
Midnight (K.B.)
Scaldis (H.F.)
Ram I (K.B.)
Chateau (K.B.)
Bristol (K.B.)
Nassau (K.B.)
Glade (K.B.)
LSDi005)

May
6.0
5.3
6.0
6.0
5.0
4.7
4.7
4.7
5.0
4.3
4.3
4.0
4.3
4.3
3.3
4.0
•3.7
3.3
1.7

June

July

Aug

Sept

Oct

Mean

6.3
6.0
5.3
6.0
6.0
5.7
4.7
5.7
6.0
4.3
7.0
5.3
4.3
5.0
5.7
5.0
3.7
4.3
1.7

5.0
4.7
4.7
4.3
4.0
4.3
4.7
4.7
3.7
4.0
4.7
4.3
4.0
4.0
4.3
3.0
3.0
2.7
2.3

4.7
5.0
5.3
4.7
5.3
4.7
4.7
4.7
4.3
4.3
4.7
4.3
4.0
4.0
3.7
4.0
3.0
3.0
2.2

6.3
6.3
5.7
6.3
5.7
5.7
6.0
5.0
5.3
5.7
4.7
4.7
5.0
4.3
4.3
4.7
3.3
3.7
2.3

5.3
5.7
5.7
5.3
5.7
5.3
5.7
5.3
5.0
6.0
3.0
4.7
5.0
4.0
3.3
4.0
3.0
2.7
1.9

5.6
5.5
5.4
5.4
5.3
5.1
5.1
5.0
4.9
4.8
4.7
4.6
4.4
4.3
4.1
4.1
3.3
3.3
1.7

Quality based on a scale of 9 to 1: 9 = best quality, 6 = lowest acceptable quality, and 1 = poorest quality

•V

19

USGA Buffalograss Trial -1994
N. E. Christians
The USGA buffalograss trial consists of 5 buffalograss (
dactyloides) varieties developed as
part of the USGA turfgrass breeding program that are being compared to a standard buffalograss
variety 'Texoka'.
The trial was established in August, 1988, and suffered considerable winter kill because of the late
planting date. Only variety 84-315 survived the first winter in a satisfactory condition. In November
1989, plugs of all varieties were established in the greenhouse and maintained during the winter of
1989-1990. All six field plots were reestablished in the last week of May, 1990. The summer of 1990
was very wet. These plugs became well established during the growing season and all reached 100%
cover by dormancy in September, 1990.
The first quality ratings were taken in 1991 and the data included in this report is from the third full
season of data collection (Table 8). Visual quality was based on a scale of 9 to 1: 9 = best quality, 6
= lowest acceptable quality, and 1 = poorest quality. In 1994, 84-315 was the highest rated variety.
Varieties 84-304 and 84-409 were severely damaged during the winters of 1993 and 1994. Very little
grass remains on plots established to these two grasses.

Table 8. The 1994 quality ratings for the USGA buffalograss study.
Cultivar

May

June

July

Sept

Mean

1

84-315

7.0

7.0

6.7

6.7

6.8

2

84-378

4.7

6.3

7.3

6.0

6.1

3

TEXOKA

6.3

5.7

6.0

5.0

5.8

4

84-609

4.2

2.3

3.3

5.0

3.8

5

84-304

2.3

1.3

1.0

1.3

1.5

6

84-409

1.0

1.0

1.3

1.3

1.2

l s d (0.05)

3.7

1.9

1.7

2.4

1.8

>

Quality based on a scale of 9 to 1: 9 = best quality, 6 = lowest acceptable quality, and 1 = poorest
quality

20

Green Height Bentgrass Cultivar Trial 1994
(Native Soil)
-

N. E. Christians and J. D. Dickson
This is the first year of data from the Green Height Bentgrass Cultivar trial established in the fall of
1993. Data collection began after the cultivars were fully established in July. The area was maintained
at a 0.5 in. mowing height in 1994 and will be lowered to 3/16 in. in 1995. This is a National Turfgrass
Evaluation (NTEP) trial and is being conducted at several research stations in the U.S. It contains 28
cultivar including some of the newest seeded varieties available and a number of experimental varieties.
The cultivars are to be maintained with a fertilizer program of 1/4 lb N applied at 14-day intervals with
an approximate total of 4 to 5 lbs of N/1000 ft2/growing season. Fungicides are used as needed in a
preventative program. Herbicides and insecticides are applied as needed.
Table 9 contains the averages of monthly visual quality ratings for July through October 1994. This is
the initial data from this study and the varieties were maintained at a higher than normal mowing height
during this establishment year. The study will be conducted for several years and data will be needed
from more years before conclusions can be drawn concerning the adaptation of these cultivars to Iowa
conditions. Earlier years of this report contain several years of data on older green height bentgrass
studies.
Table 9. The 1994 ratings for the green height bentgrass trial.
Cultivar

July

August

1

Sept

Oct

7.0
7.0
5.7
7.0
A-4
6.7
6.3
6.7
6.7
2
Cato
6.7
7.3
6.7
5.7
L-93
3
7.0
7.3
7.0
Providence
4.7
4
6.3
7.3
5.0
6.3
G-6
5
6.7
6.0
6.7
Southshore
5.3
6
6.7
6.7
5.3
5.7
A-l
7
5.7
Crenshaw
8
5.0
6.3
6.3
4.7
6.7
6.3
5.3
9
SYN 92-1-93
5.3
6.7
SYN 92-5-93
4.7
6.3
10
6.0
6.0
Regent
6.3
4.3
11
5.7
5.7
6.0
12
SR 1020
5.0
5.7
6.0
6.7
3.7
ISI-AP-89150
13
5.7
6.0
14
5.0
5.3
Lopez
5.7
5.3
6.0
15
Pennlinks
5.0
6.0
6.3
16
G-2
4.0
5.3
5.7
6.0
17
MSUEB
4.7
5.3
5.3
6.3
5.3
18
BAR WS 42012
4.0
5.3
5.3
19
5.3
Penncross
5.0
5.0
5.7 '
20
SYN 92-2-93
5.0
5.3
5.0
21
6.3
18th Green
3.7
5.7
5.3
22
5.3
Trueline
4.3
5.7
5.0
5.3
3.7
23
Pro/Cup
5.3
5.7
24
5.3
DG-P
3.3
4.3
4.0
5.0
25
SYN-1-88
4.7
3.3
3.7
4.0
26
BAR AS 493
3.7
3.0
3.7
27
4.3
Seaside
3.3
2.7
3.7
28
3.7
Tendenz
2.7
3.7
1.6
1.1
1.1
LSD*.*)
1.5
Quality based on a scale of 9 to 1: 9 = best quality, 6 = lowest acceptable quality, and 1 = poorest quality.

21

Mean
6.7
6.6
6.6
6.5
6.3
6.2
6.1
5.8
5.8
5.8
5.7
5.6
5.5
5.5
5.5
5.4
5.4
5.3
5.3
5.3
5.2
5.2
4.8
4.7
4.3
3.6
3.5
3.4
0.9

Fairway Height Bentgrass Study -1994
N. E. Christians and J. D. Dickson
This is the first year of data from the Fairway Height Bentgrass Cultivar trial established in the fall of 1993.
Data collection began after the cultivars were fully established in July. The area was maintained at a 0.5 in.
mowing height in 1994 and will be maintained at that height throughout the study. This is a National
Turfgrass Evaluation (NTEP) trial and is being conducted at several research stations in the U.S. It contains
21 cultivar including standard cultivars, some of the newest seeded cultivars available and a number of
experimental varieties.
The cultivars are to be maintained with 4 to 5 lbs of N/1000 ft2/growing season. Fungicides are used as
needed in a preventative program. Herbicides and insecticides are applied as needed.
Table 10 contains monthly visual quality ratings from July through October 1994. Visual quality is based
on a scale of 9 to 1: 9 = best quality, 6 = acceptable quality, and 1 = poorest quality. This was the
establishment year for this study and more years of data will be needed before conclusions can be drawn.
Earlier years of this report contain several years of data on older fairway height bentgrass studies.
Table 10. The 1994 quality ratings for the fairway height bentgrass study.
Cultivar

July

August

Sept

Oct

Mean

1

Cato

7.0

7.0

7.0

7.0

7.0

2

Penneagle

6.7

6.3

6.7

7.3

6.8

3

Southshore

6.3

6.7

6.7

7.3

6.8

4

Providence

5.7

6.7

6.7

7.3

6.6

5

Crenshaw

7.0

6.3

6.3

5.7

6.3

6

G-6

6.0

6.0

5.7

7.3

6.3

7

Trueline

6.0

6.3

5.7

6.3

6.1

8

BAR WS 42102

5.7

5.7

6.0

6.7

6.0

9

Lopez

6.3

5.7

5.3

5.7

5.8

10

G-2

5.0

5.0

6.0

6.7

5.7

11

Pro/Cut

5.3

5.7

5.7

6.0

5.7

12

18th Green

5.0

6.7

5.7

5.0

5.6

13

DF-1

5.3

5.3

6.0

5.7

5.6

14

Penncross

5.7

5.3

5.0

5.3

5.3

15

SR 7100

5.0

4.3

4.0

4.3

4.4

16

ISI-AT-90162

4.0

4.3

4.3

4.7

4.3

17

Seaside

3.3

4.0

4.3

4.3

4.0

18

OM-AT-90163

3.7

4.3

3.7

4.0

3.9

19

BAR AS 493

3.0

4.3

4.3

3.7

3.8

20

Tendenz

3.7

3.3

4.0

4.0

3.8

21

Exeter

2.7

3.3

3.7

3.0

3.2

LSDi005)

1.2

1.2

1.3

1.5

0.8

’

Quality based on a scale of 9 to 1: 9 = best quality, 6 = lowest acceptable quality, and 1 = poorest quality.

22

Herbicide and
Growth Regulator
Studies

F

Preemergence Weed Control Study 1994
-

B. R. Bingaman and N. E. Christians
Several herbicides were tested for efficacy as preemergence materials for crabgrass control in turf areas.
This study was conducted at the Iowa State University Horticulture Research Station north of Ames,
Iowa. The site of the experiment was an established Indigo Kentucky bluegrass area. The soil was a
Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with an organic matter content of 3.5%, a pH of
6.25, 23 ppm P, and 114 ppm K. This area was seeded prior to the beginning of this testing with a
mixture of large hairy crabgrass (Digitaria sanguinalis (L.) Scop.) and smooth crabgrass (Digitaria
ischaemum (Schreb.) Schreb. ex Muhl). Supplemental irrigation was applied as needed throughout the
duration of the study.
Individual experimental plots were 5 x 5 ft and there were 20 treatments including 19 herbicides and an
untreated control (Table 11). The study was arranged in a randomized complete block design and 3
replications were conducted.
All treatments (except the Dimension + fertilizer material) were applied on April 27, 1994. The
Dimension + fertilizer product (treatment #14) was received and applied on April 30, 1994. A 6 week
sequential application of Dimension 1EC (treatment #15) was made on June 9. Cardboard containers
with holes punched in the lids were used as shaker dispensers for the granular products. A backpack
carbon dioxide sprayer equipped with 8006 nozzles with a spray pressure of 20-25 psi was used to apply
the liquid materials. Liquid treatments were applied with the equivalent of 3 gal water/1000 ft2.
Temperatures for the first week after treatment application were quite cool with subfreezing low
temperatures recorded for April 28 thru May 2. Rainfall occurred on the first 3 days following treatment
application.
Phytotoxicity and visual quality data were taken on May 11(14 days after treatment) and at 2 week
intervals thereafter throughout the duration of the study. Crabgrass germination was not evident until
early June and slow growth and development of the plants prevented taking percentage of crabgrass
cover data until July 6. Subsequent percentage data were collected on July 15 and 21 and August 2 and
19.
Data were analyzed with the Statistical Analysis System version 6.06 (SAS Institute, 1989) by using the
Analysis of Variance (ANOVA) to test the significance of crabgrass control among the various herbicide
materials. Least significant difference (LSD) tests were used to compare means among the treatments.
No visible toxicity was observed at any time during the study (Table 11). None of the treatments were
100% effective. Ronstar, Lesco Pre-M at 3.00 lb ai/A, Dimension, Scott’s Halts and Dacthal came close
to providing complete control. The Scott’s Pre-M, at the low application rate of 1.18 lb ai/A, was not
effective. Several of the experimental (EXP) materials were also ineffective.

23

O N O O ' O ' O ' O ' O ' O ' O N O ' O ' O ' O ' O

O'

O'

O

O'

O'

ON

ON

ON

O'

O'

O'

On

O'

O'

On

O'

O'

On

On

O'

O'

O'

O'

o

On

O

O'

O'

On

On

On

O

O

O

On

On

On

On

O'

O'

O

On

O'

O'

On

On

On

O'

O'

O'

O'

O'

O'

On

O

On

On

O'

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O'

O'

O

On

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On

On

On

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O'

O'

O'

O'

On

On

On

On

On

On

On

On

On

On

On

O'

ON

O'

O'

Table 11. The visual quality1of Kentucky bluegrass treated with several preemergence herbicides2.

O N O ' O ' O ' O N O

N

O

On

O

O

O

On

n

O O

n

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O

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25

Postemergence Crabgrass Control Study - 1994
B. R. Bingaman and N. E. Christians
Several herbicides were tested for efficacy as postemergence materials for crabgrass control in turf areas.
Dimension, Barricade, Acclaim, Lesco Pre-M, Dimension + fertilizer, HOE 46360 (3.1 EW) and HOE
46360 (0.57 EW) were applied at a range of rates and at different stages of crabgrass development.
Preemergence (PRE), early- (EPO), mid- (MPO), and late-postemergence (LPO) applications were made
(Table 13). This study was conducted at the Iowa State University Horticulture Research Station north
of Ames, Iowa. The site of the experiment was an established Ram I Kentucky bluegrass area. The soil
was a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with an organic matter content of 3.5%, a pH
of 6.25, 23 ppm P, and 114 ppm K. This area was seeded prior to the beginning of this testing with a
mixture of large hairy crabgrass (
Digitariasanguinalis (L.) Scop.) and smooth crabgrass (
ischaemum (Schreb.) Schreb. ex Muhl). Supplemental irrigation was applied as needed throughout the
duration of the study.
Individual experimental plots were 5 x 5 ft and there were 27 herbicide treatments and an untreated
control (Table 13). The study was arranged in a randomized complete block design with 3 replications.
Cardboard containers with holes punched in the lids were used as shaker dispensers for the granular
products. A backpack carbon dioxide sprayer equipped with 8006 nozzles with a spray pressure of 20-25
psi was used to apply the liquid materials. Liquid treatments were applied with the equivalent of 3 gal
water/1000 ft2.
All PRE materials were applied before crabgrass germination. The HOE premix treatments 26, 27, and
28 were applied on April 27. These treatments were mixed incorrectly so the proper rates were applied
on April 30 as treatments 2, 3, and 4. Temperatures for the first week after treatment application were
quite cool and subfreezing low temperatures were recorded for April 28 thru May 2. Rainfall occurred
on April 28, 29 and 30.
Crabgrass germination was detected on June 8 and the EPO products were applied on June 22 when the
plants were in the 3-4 leaf stage but untillered. Within 24 hours after application, 3.3 inches of rainfall
were received. Mid-postemergence applications were made on July 13 when the crabgrass was in the 12 tiller stage. There was no substantial rainfaH until July 27.
Once the crabgrass was in the 3-5 tiller stage the LPO materials were applied. Application was made on
August 4 and rainfall occurred on August 9-12.
The plots were surveyed throughout the duration of the study for possible phytotoxicity to the herbicide
products. Visual quality data were taken to assess phytotoxicity at approximately 2 week intervals
beginning May 11 and ending on August 19. Data collection was scheduled to correspond with the
application dates of the PRE, EPO, MPO, and LPO products.
Percentage of crabgrass cover data were not taken until July 15 because of late crabgrass germination,
and slow plant growth and development. Percentage data were subsequently collected on July 21 and
August 2 and 19.
The Statistical Analysis System version 6.06 (SAS Institute, 1989) and the Analysis of Variance
(ANOVA) were utilized to test the significance of crabgrass control among the various herbicide
treatments. Least significant difference (LSD) tests were used to compare means among the treatments.

26

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1994

Dithiopyr

Pre-

andPostemergence Weed Con

B. R. Bingaman and N. E. Christians
Seven fertilizer and crabgrass herbicide materials were evaluated for their suitability as nitrogen sources
for Kentucky bluegrass and for their efficacy in controlling crabgrass. Crab-Buster Plus, Crab-Buster
Plus II, Crab-Buster Plus III, Super Team, Scott’s Halts, Green Charm, and an untreated check
(consisting of a 29-4-10 fertilizer) were supplied by Parcel Inc. for screening. Each material was applied
to 2 plots. One plot received a preemergent (PRE) application before crabgrass germination had begun.
The other was given an early postemergent (POST) application when the crabgrass was in the 2-3 leaf
stage but before tillering had begun.
This study was conducted at the Iowa State University Horticulture Research Station north of Ames,
Iowa. The site of the experiment was an established Indigo Kentucky bluegrass area. The soil was a
Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with an organic matter content of 3.5%, a pH of
6.25, 23 ppm P, and 114 ppm K. This area was seeded prior to the beginning of this testing with a
mixture of large hairy crabgrass (
Digitariascmguinalis (L.) Scop.) and smooth crabgrass (
ischaemum (Schreb.) Schreb. ex Muhl). Supplemental irrigation was applied as needed throughout the
duration of the study.
Individual experimental plots were 5 x 5 ft and there were 14 treatments including 13 herbicides and a
control (Table 15). The study was arranged in a randomized complete block design with 3 replications.
Cardboard containers with holes punched in the lids were used as shaker dispensers for the granular
products. All PRE materials were applied on April 27 before crabgrass germination was detected.
Temperatures for the first week after treatment application were quite cool with subfreezing low
temperatures recorded for April 28 thru May 2. Rainfall occurred on April 28, 29 and 30.
Crabgrass germination was detected on June 8 and the POST products were applied on June 21 when the
plants were in the 2-4 leaf stage with no tillering. Within 48 hours after application, 3.3 inches of
rainfall were received.
Kentucky bluegrass was evaluated for possible phytotoxicity to herbicide products. Visual quality data
were taken to assess phytotoxicity at approximately 2 week intervals beginning May 11 and ending
August 19. Data collection was scheduled to correspond with application dates of PRE and POST
products.
Percent crabgrass cover was not evaluated until July 6 because of late crabgrass germination, and slow
plant growth. Percentage data were subsequently collected on July 15, July 21, and August 19.
Data were analyzed with Statistical Analysis System version 6.06 (SAS Institute, 1989) by using
Analysis of Variance (ANOVA) to test significance of crabgrass control among various herbicide
materials and times of application. Least significant difference (LSD) tests were used to compare means
among treatments.
No turfgrass phytotoxicity was observed during the study (Table 15). Crab-buster was generally quite
effective in both pre- and post-applications (Table 16). The Scott's material was initially effective, but
some breakthrough occurred in late summer.

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d>

Broadleaf Weed Control Study 1994
-

B. R. Bingaman and N.E. Christians
Several herbicides were tested for efficacy as postemergence materials for broadleaf weed species in turf
areas. Products from, DowElanco, O. M. Scott & Sons Co., PBI Gordon, Rhone-Poulenc Ag Company,
and Sandoz Agro Inc. were included.
This study was conducted at the Iowa State University Horticulture Research Station north of Ames, Iowa.
The site of the experiment was a common Kentucky bluegrass area with a heavy infestation of dandelion
( Taraxacum officianale Weber) and white clover (
Trifoliurepens
loamy, mixed, mesic Aquic Hapludoll) with an organic matter content of 3.5%, a pH of 5.95, 28 ppm P,
and 162 ppm K.
Individual experimental plots were 5 x 10 ft and there were 19 treatments including 18 herbicides and an
untreated control (Table 17). The experimental design was a randomized complete block with 3
replications.
The 5 x 1 0 f t plots that received granular Confront, S-4779, and S-4953, were subdivided into 5 x 5 ft plots
so that a comparison study could be conducted. Granular materials in subplots were applied to either dry
or wet foliage.
Treatments were applied on 26 May 1994, between 6:00 and 8:15 p.m. Cardboard containers with holes
punched in the lids were used as shaker dispensers for the granular products. A backpack carbon dioxide
sprayer equipped with 8006 nozzles with a spray pressure of 20-25 psi was used to apply the liquid
materials. Liquid treatments were applied with the equivalent of 3 gal water/1000 fit2. A sprayer also was
used to moisten the foliage in the subplots being treated with Confront S-4779 and S-4953 on wet foliage.
Weather conditions after treatment application were very favorable. Temperatures were seasonable and no
rainfall occurred until June 1, 1994.
On June 2 and June 9 (7 and 14 days after treatment, respectively) the degree of damage to the weeds in
each individual plot was recorded by assessing the weeds for leaf curl, discoloration, and mortality.
Damage was determined using a visual rating scale from 9 to 1, with 9 indicating dead weeds and 1
indicating no damage. Percentage weed cover was estimated 4 and 6 weeks after treatment applications.
Data for dandelion, knotweed {Polygonum aviculare L.), plantain {Plantago lanceolata L.), black medic
( Medicago lupulina L.), oxalis {Chalis stricta L.), curly dock (
crispus L.), and white clover were
recorded on June 22. On July 6 percentages were recorded for these 7 species and for purslane {Portulaca
olerácea L.), prostrate spurge {Euphorbia supina Raf. ex Boiss.), velvetleaf {Abutilón theophrasti Medic.),
redroot pigweed {Amaranthus retroflexus L.), Pennsylvania smartweed {Polygonum pensylvanicum L.),
and common lambsquarters {Chenopodium album L.). No additional data were taken after July 6 because
germination of new plants had begun.
Data were analyzed with Statistical Analysis System version 6.06 (SAS Institute, 1989) by using Analysis
of Variance (ANOVA) to test significance of broadleaf weed control among various herbicide materials.
Least significant difference (LSD) tests were used to compare means among treatments.
Buctril, a contact herbicide, provided the quickest knockdown of weeds (Table 17), however, dandelion
and clover both recovered in Buctril treated plots by July 6. The granular Confront materials (treatments
9-12) were effective on both dry and wet tissue. The addition of Garlón (Tryclopyr) to Vanquish
(Dicamba) provided improved clover control at the 0.125 lb ai/A level of Vanquish. Trimec Classic and
Super Trimec provided near complete weed control in all plots.

32

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'All herbicide materials applied 5/26/94.
NS = not significantly different at the 0.05 level.

o o o o

_______LSDqq5_______________________________

Table 20. The percentage of cover of several broadleaf weed species on July 6, 1994 in Kentucky bluegrass 42 days after application of postemergence herbicides'.

U

TheEffect o f Two Adjuvants on Plant Response to Primo
B. R. Bingaman and N. E. Christians
Primo growth regulator was evaluated for efficiency of uptake when applied in combination with
different adjuvants. This study was conducted at the Iowa State University Horticulture Research Station
north of Ames, Iowa. The experimental plot was an established Midnight Kentucky bluegrass area. The
soil was a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with an organic matter content of 3.3%,
a pH of 6.7, 9 ppm P and 86 ppm K. This site was not fertilized this season.
Individual experimental plots were 5 ft x 5 ft and there were 10 treatments. Primo was applied at 3
different rates and at 2 different rates in combination with Turfex and X77. Both adjuvants were applied
without Primo and an untreated control also was included.
The study was arranged in a randomized complete block design. Three replications were conducted and
3 ft barrier rows were left between replications.
All treatments were applied on July 22 . Prior to application the experimental site was examined and the
turf was found to be quite uniform in color, density, and overall quality. It was sunny with a temperature
in the mid 80's and a southerly breeze. The grass foliage was dry.
A backpack carbon dioxide sprayer equipped with 8006 nozzles with a spray pressure of 20-25 psi was
used to apply the materials. Liquid treatments were applied with the equivalent of 3 gal water/1000 ft2.
Rainfall did not occur until July 27 and was sporatic for the duration of this study. Supplemental
irrigation was used to provide adequate moisture to maintain the grass in good growing condition.
Visual quality and fresh clipping weight data were taken at 7 day intervals on July 29 and August 4. The
next set of data (21 days after treatment) were taken on August 16 because of rainfall, subsequent
saturated ground and wet foliage. The experimental area was very dry 7 days later and the data
collection scheduled for this day was delayed until August 25 so that supplemental irrigation could be
used.
Visual quality assessments were based on colon, density, and phytotoxicity and recorded using a scale of
9 to 1 (9 = best, 6 = acceptable, and 1 = poorest quality). Mowing height for collecting clippings was 2".
Data were analyzed with the Statistical Analysis System version 6.06 (SAS Institute, 1989) by using the
Analysis of Variance (ANOVA) to test the significance of the treatments on the visual quality and
clipping weights. Least significant difference (LSD) tests were used to compare means among the
treatments.

37

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Plant Growth Regulators Applied at Low Volumes o f Water
B. R. Bingaman and N. E. Christians
Primo growth regulator was evaluated for efficiency of uptake and phytotoxicity when applied with low
volumes of water. This study was conducted at the Iowa State University Horticulture Research Station
north of Ames, Iowa. The experimental plot was an established Kentucky bluegrass area. The soil was a
Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with an organic matter content of 3.0%, a pH of
7.05, 8 ppm P, and 67 ppm K. This site was not fertilized for the 1994 growing season.
Individual experimental plots were 5 ft x 5 ft and there were 6 treatments (5 with Primo and 1 untreated
control). The study was arranged in a randomized complete block design. Three replications were
conducted and there were 3 ft barrier rows between replications.
All treatments were applied on May 27 at 9:00 a.m. to an experimental site that was uniform in color,
density, and overall quality. It was mostly sunny with a temperature in the mid 60's and a slight,
southerly breeze. The grass foliage was dry. Primo was used at the label rate for Kentucky bluegrass
(0.75 ft oz/1000 ft2) in volumes of water ranging from 40-800 GPA.
A backpack carbon dioxide sprayer equipped with 8006 nozzles with a spray pressure of 20-25 psi was
used to apply materials. Uniform application of Primo in 40 GPA of water was quite difficult. When
converted to an area of 25 ft2, the volume was so small that it was not possible to make 1 pass of the
sprayer over the entire individual plot. The other volumes were sufficient to make at least 2 passes over
the individual plots.
Rainfall did not occur until June 1 and was sporadic for the duration of this study. Turf was irrigated as
needed to prevent wilting.
Visual quality and fresh clipping weight data were taken weekly for 6 weeks from 3 June to 8 July.
Visual quality assessments were based on color, density, and phytotoxicity and recorded using a scale of
9 to 1 (9 = best, 6 = acceptable, and 1 = poorest quality). Mowing height for collecting clippings was 2
inches.
Data were analyzed with Statistical Analysis System version 6.06 (SAS Institute, 1989) by using
Analysis of Variance (ANOVA) to test significance of treatments for visual quality and clipping
weights. Least significant difference (LSD) tests were used to compare means among the treatments.

39

<U Cd
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Table 23. Visual quality1 of Kentucky bluegrass treated with Primo in different volumes of water2.

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Cd .tS

The Effect o f Spring Applications of Ethofumesate (Prograss) on a Golf Course
Fairway at Indian Creek Country Club in Nevada, Iowa
J. B. Unruh and N. E. Christians
Ethofumesate (Prograss) is marketed as an annual bluegrass
annua) control for golf course
fairways. It is labeled for use on Kentucky bluegrass (Poapratensis), perennial ryegrass (Lolium
perenne), and creeping bentgrass (Agrostis palustris) maintained at fairway mowing heights.
Prior research on the efficacy of spring applications of ethofumesate following fall application showed
ethofumesate to be effective at controlling annual bluegrass in creeping bentgrass and perennial ryegrass
and spring application was subsequently added to the Prograss label in 1992. A single spring
application, not preceded by fall applications, has been ineffective. Because of the sensitivity of
Kentucky bluegrass to ethofumesate, more information on effective rates needs to be obtained. The
objective of this study was to assess annual bluegrass control from spring applications of ethofumesate
that followed three fall applications of 0.75 lb ai/acre each.
The experiment was initiated on September 16, 1994. The West half of a North - South oriented
Kentucky bluegrass—Perennial Ryegrass fairway at Indian Creek Country Club in Nevada, Iowa was
treated with 0.75 lb ai/acre on September 16, October 14, and November 10. Spring treatments were
applied on April 28, 1995 as indicated in Table 25. Spring treatments were arranged as a randomized
complete block study with 3 replications. Plots measured 180 ft. by 10 ft. Estimates of percent annual
bluegrass were taken on May 18, 1995 (Table 25).
The initial population of annual bluegrass was estimated to be 75% on the untreated (East) half of the
fairway. The fall application of ethofumesate alone resulted in a reduction of annual bluegrass to 38% in
the area of the fairway that had received 3 fall applications but no spring application (control), a nearly
50% reduction of annual bluegrass. Spring applications of 0.25 and 0.5 lb ai/A numerically reduced
annual bluegrass infestation to 22%, although this reduction was not statistically significant. The 0.75 lb
ai/A Prograss spring treatment reduced annual bluegrass to 5% of the total stand, a 93% reduction from
the untreated section of the fairway.
We observed no damage to the Kentucky bluegrass or to the Perennial Ryegrass at any time during the
study.

Table 25. The effect of spring applications of Ethofumesate (Prograss) on a golf course fairway
following 3 applications in the fall.
Treatment

lb ai / acre

% Poa annua

0

38

Prograss EC

0.25

22

Prograss EC

0.5

22

Prograss EC

0.75

5

Control

LSD o05

—

41

17

m

Turfgrass Disease
and Insect Research

Evaluation o f Fungicides for Control of Snow Molds
on Creeping Bentgrass at Nashua, I A 1994-1995
M. L. Gleason
The trial was conducted on a bentgrass green (cv. unknown) at the Nashua Town and Country Club Golf
Course, Nashua, IA. This green has a high thatch content, is subject to drifting snow, and has had severe
outbreaks of snow mold in most of the last 10 years. The experimental design was a randomized
complete block with 4 replications. All plots measured 4 ft x 5 ft. Fungicides were applied on
November 14, 1994, using a modified bicycle sprayer at 30 psi and a dilution rate of 5 gal/1000 fit2.
Snow cover persisted from about December 8, 1994, until March 13, 1995. On March 15, symptoms of
gray snow mold were evident on the part of the green where snow cover persisted longest. Snow mold
development on untreated check plots was moderate, with an average of about 10% of the plot area
symptomatic (Table 1). About half of the fungicide treatments gave significantly better control of snow
mold than the untreated check. Several treatments were completely free of symptoms, including
Thalonil 90 DF at 4.75 oz + Chipco 26019 50 WDG at 2 oz/1000 ft2, Chipco at 2 oz + Daconil Ultrex
82.5 WDG at 5 oz, EXP 10452 50 WG at 4 oz + Daconil Ultrex at 5 oz, Sentinel at 0.33 oz, Sentinel at
0.33 oz + Chipco at 2 oz, FF2 at 16 oz a.i., Banner 1.1 EC at 3 oz + CGA 173 at 0.5 oz, and Curalan DF
at 4 oz + Daconil 2787 at 8 oz. No phytotoxicity symptoms were observed.

Table 26. Snow Mold Trials, 1994-95, Nashua Town and Country Club, Nashua, Iowa.
Company

Products

Rate/1000 ft2

Check

—

1.75 abc2

Terra

Thalonil 90DF
-r Chipco 26019 50WDG

4.75 oz
2.0 oz

0.00 e

Thalonil 4L
+ Chipco 26019 50WDG

8.0 oz
2.0 oz

0.50 cde

Cleary

Rhone-Poulenc

Sandoz

Disease rating1

Defend 2F

24 fl oz

0.25 de

3336 50 WP
-ft Spotrete 75 WDG

2.0 oz
6.0 oz

1.25abcde

Spotrete 75 WDG
-ft Clearspray

8.0 oz
2.0 fl oz

0.5 cde

Spotrete 75 WDG

8.0 oz

1.75 abc

Chipco 26019 50 WDG
-ft Daconil 2787 4.17SC

4.0 oz
8.0 oz

0.25 de

Chipco 26019 50 WDG
-ft Daconil Ultrex 82.5WDG

4.0 oz
5.0 oz

0.25 de

Chipco 26019 50 WDG
-ft Daconil Ultrex 82.5WDG

2.0 oz
5.0 oz

0.00 e

Chipco 27019 50 WDG
-ft PCNB 75WP

2.0 oz
2.7 oz

0.50 cde

EXP 10452 50WG
-ft Dac.onil Ultrex 82.5WDG

4.0 oz
5.0 oz

0.00 e

Chipco 26019 50 WDG

4.0 oz

2.25 a

Chipco 26019 50 WDG
-ft Cleary’s 3336 50WP

4.0 oz
4.0 oz

1.5 abed

EXP 10452 50WG

4.0 oz

0.25 de

Sentinel
-ft PCNB 75WP

0.33 oz
4.0 oz

0.25 de

Sentinel

0.33 oz

0.00 e

42

Company

Products

Rate/1000 ft2

Disease rating1

Sandoz

Sentinel
+ Chipco 26019 WDG

0.33 oz
2.0 oz

0.00 e

S-4902

8 oz ai

0.75 bcde

S-4902

16 oz ai

0.00 e

FF2

8 oz ai

0.25 de

Banner l.l EC
+ PCNB 75 WP

3.0 oz
4.0 oz

1.25 abcde

Banner 1.1 EC
+ CGA 173

3.0 oz
0.5 oz

0.00 e

Curalan DF

4.0 oz

1.25 abcde

Curalan DF
+ Daconil 2787

4.0 oz
8.0 oz

0.00 e

O.M. Scott

Ciba

BASF

'0=no disease, 1=<5% plot area diseased, 2=5-15%, 3=15-30%, 4=30-50%, 5=>50%
2 means of 4 replications. Means followed by the same letter are not significantly different (DMRT, P=0.05)

43

Evaluation of Fungicides for Control of Pink and Gray Snow Mold
at the ISU Horticulture Farm, Gilbert, I A - 1994-1995
M. L. Gleason
Separate trials for pink snow mold (pathogen: Microdochium mvaje) and gray snow mold (Tvphula
incamata) were conducted on a 'Penncross' creeping bentgrass green at the Iowa State University
Horticulture Farm's turfgrass research area near Gilbert, IA. In order to help insure disease activity, the
test plots were inoculated with the target pathogens and covered with straw and shade cloth to simulate
snow cover according to the protocol of Schumann (Fungicide and Nematicide Tests 46:304, 1991). The
experimental design was a randomized complete block with 4 replications. All plots measured 3 ft x 5 ft.
Approximately 75 g of inoculum ( a combination of infested rye grain and dried fragments of colonized
agar) per 15 ft2 plot was spread on the plots on November 7, 1994. The pink snow mold plot received
only inoculum infested with the pink snow mold pathogen, and the gray snow mold plot received only
inoculum infested with the gray snow mold pathogen. Fungicides were applied on November 8, 1994,
using a modified bicycle sprayer at 30 psi and a dilution rate of 5 gal/1000 ft2. On November 11, 1994,
the plots were covered with a 6" layer of oat straw, then a layer of shade cloth (55% shade) was placed
over the straw and secured to the turf with metal staples.
Snow cover persisted from about December 9, 1994, until March 1, 1995. When the shade cloth and
straw were removed on March 14, 1995, symptoms of gray snow mold were evident on the gray snow
mold plot and symptoms of pink snow mold were evident on the pink snow mold plot. However, the
symptoms were atypical in that patches of affected grass were not bleached to as light a tan color as
patches located outside the covered areas. Snow mold development on untreated check plots was
moderate, with an average of about 20% of the area symptomatic in both the gray and pink snow mold
plots. All of the pink snow mold and gray snow mold treatments gave significantly better control than
the untreated check, and many were completely symptom-free. No phytotoxicity symptoms were
observed.
These trials indicated the feasibility of the method of Schumann (inoculation plus covering) for
conducting pink and gray snow mold trials in central Iowa.

Table 27. Pink Snow Mold Trials, 1994-1995.
Company
Terra

Cleary

Rhone-Poulenc

Products

Rate/1000 ft2

Disease rating1

Check

—

3.25 a2

Thalonil 90DF
+ Chipco 26019 50WDG

4.75 oz
2.0 oz

0.25 be

Thalonil 4L
+ Chipco 26019 50WDG

8.0 oz
2.0 oz

0.00 c

Defend 2F

24 fl oz

0.50 be

3336 50 WP
+ Spotrete 75 WDG

2.0 oz
6.0 oz

0.75 be

Spotrete 75 WDG
+ Clearspray

8.0 oz
2.0 fl oz

0.25 be

Spotrete 75 WDG

8.0 oz

0.75 be

Chipco 26019 50 WDG
+ Daconil 2787 4.17SC

4.0 oz
8.0 oz

0.75 be

Chipco 26019 50 WDG
+ Daconil Ultrex 82.5WDG

4.0 oz
5.0 oz

0.00 c

44

Company

Products

Rate/1000 ft2

Disease rating1

Rhone-Poulenc

Chipco 26019 50 WDG
+ Daconil Ultrex 82.5WDG

2.0 oz
5.0 oz

0.25 be

Chipco 27019 50 WDG
+ PCNB 75WP

2.0 oz
2.7 oz

0.00 c

EXP 10452 50WG
+ Daconil Ultrex 82.5WDG

4.0 oz
5.0 oz

0.00 c

Chipco 26019 50 WDG

4.0 oz

0.25 be

Chipco 26019 50 WDG
+ Cleary’s 3336 50WP

4.0 oz
4.0 oz

0.00 c

EXP 10452 50WG

4.0 oz

0.00 c

Sentinel
+ PCNB 75WP

0.33 oz
4.0 oz

0.00 c

Sentinel

0.33 oz

0.00 c

Sentinel
+ Chipco 26019 WDG

0.33 oz
2.0 oz

0.25 be

O.M. Scott

S-4902

8 oz ai

0.25 be

•

S-4902

16 oz ai

0.00 c

Banner 1.1 EC
+ PCNB 75 WP

3.0 oz
4.0 oz

0.00 c

Banner 1.1 EC
+ CGA 173

3.0 oz
0.5 oz

0.00 c

Curalan DF

4.0 oz

0.25 be

Curalan DF
+ Daconil 2787

4.0 oz
8.0 oz

0.25 be

Sandoz

Ciba

BASF

'0=no disease, 1=<5% plot area diseased, 2=5-15%, 3=15-30%, 4=30-50%, 5=>50%
2 means of 4 replications. Means followed by the same letter are not significantly different (DMRT, P=0.05)

Table 28. Gray Snow Mold Trials, 1994-1995.
Company
Terra

Cleary

Rhone-Poulenc

Products

Rate/1000 ft2

Disease rating1

Check

—

3.00 a2

Thalonil 90DF
-r Chipco 26019 50WDG

4.75 oz
2.0 oz

1.00 b

Thalonil 4L
+ Chipco 26019 50WDG

8.0 oz
2.0 oz

0.00 b

Defend 2F

24 fl oz

1.25 b

3336 50 WP
+ Spotrete 75 WDG

2.0 oz
6.0 oz

0.50 b

Spotrete 75 WDG
+ Clearspray

8.0 oz
2.0 fl oz

0.00 b

Spotrete 75 WDG

8.0 oz

0.50 b

Chipco 26019 50 WDG
+ Daconil 2787 4.17SC

4.0 oz
8.0 oz

0.25 b

Chipco 26019 50 WDG
+ Daconil Ultrex 82.5WDG

4.0 oz
5.0 oz

0.75 b

Chipco 26019 50 WDG
+ Daconil Ultrex 82.5WDG

2.0 oz
5.0 oz

0.50 b

Chipco 27019 50 WDG
+ PCNB 75WP

2.0 oz
2.7 oz

0.00 b

45

Company

Products

Rate/1000 ft2

Disease rating1

Rhone-Poulenc

EXP 10452 50WG
+ Daconil Ultrex 82.5WDG

4.0 oz
5.0 oz

0.00 b

Sandoz

O.M. Scott
Ciba

BASF

Chipco 26019 50 WDG

4.0 oz

0.00 b

Chipco 26019 50 WDG
+ Cleary’s 3336 50WP

4.0 oz
4.0 oz

0.25 b

EXP 10452 50WG

4.0 oz

0.00 b

Sentinel
+ PCNB 75WP

0.33 oz
4.0 oz

0.25 b

Sentinel

0.33 oz

1.00 b

Sentinel
+ Chipco 26019 WDG

0.33 oz
2.0 oz

0.25 b

S-4902

8 oz ai

0.25 b

S-4902

16ozai

0.00 b

Banner 1.1 EC
+ PCNB 75 WP

3.0 oz
4.0 oz

0.00 b

Banner 1.1 EC
+ CGA 173

3.0 oz
0.5 oz

0.00 b

Curalan DF

4.0 oz

1.00 b

Curalan DF
+ Daconil 2787

4.0 oz
8.0 oz

0.00 b

’0=no disease, 1=<5% plot area diseased, 2=5-15%, 3=15-30%, 4=30-50%, 5=>50%
2 means of 4 replications. Means followed by the same letter are not significantly different (DMRT, P=0.05).

46

Evaluation of Fungicides for Control of
Brown Patch in Creeping Bentgrass - 1994
M. L. Gleason
Trials were conducted at Veenker Golf Course on the campus of Iowa State University, Ames, IA.
Fungicides were applied to creeping bentgrass maintained at 5/32-inch cutting height, using a modified
bicycle sprayer at 30 psi and a dilution rate of 5 gal/1000 fit2. The experimental design was a randomized
complete block with three replications. All plots measured 4 ft x 5 ft. All plots were surrounded by 1-ftwide strips of untreated turf in order to help create uniform disease pressure.
Fungicide applications began on June 9 and were repeated at recommended intervals on June 16, 23, 30,
and July 7, 14, and 21.
June and July 1994 were approximately normal in rainfall and temperature, but mid-July was somewhat
cooler and drier than average. Disease development on the untreated check plots was moderate to severe
on all rating dates.
Most formulations suppressed disease significantly on each rating date. Several treatments provided
excellent control on all rating dates; two treatments, 1) Thalonil 4 L at 6.0 oz and 7-day interval, 2) EXP
10452A at 2.0 oz and 14 days, showed no disease on any rating date. Treatments that exhibited an
enhanced gree color on one or more rating dates included: Sentinel 40 WG at 28-day interval; Eagle 40
W; EXP 10452A at both rates; and Banner plus ProStar at 1- and 2-oz rates, respectively, and a 28-day
interval. No phytotoxicity symptoms were observed.
•

PCNB 75 W formulations at the 4-oz rate and 7-day intervals caused moderately severe yellowing and
browning of the turf in July and August. Sentinel 40 WG caused a slightly enhanced green color of the
turf by early August.

47

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49

Evaluation of Fungicides for Control of
Dollar Spot in ‘Penncross’ Bentgrass - 1994
M. L. Gleason
Trials were conducted at the Turfgrass Research Area of Iowa State University's Horticulture Research
Farm, Gilbert, IA. Fungicides were applied to Penncross creeping bentgrass maintained at 5/32-inch
cutting height, using a modified bicycle sprayer at 30 psi and a dilution rate of 5 gal/1000 fit2. The
experimental design was a randomized complete block with four replications. All plots measured 4 ft x 5
ft.
After inoculation of the entire plot with pathogen-infested rye grain, spray applications began on June 7.
Subsequent applications were made at specified intervals on June 14, 21, 28, and July 5, 12, and 19.
Dollar spot symptoms appeared in the plot during the week of June 19 (Table 30). Disease development
was moderately severe during late June through early July, but subsided in late July as relatively dry,
cool weather became prevalent. Almost all treatments gave significant (P=0.05) disease suppression in
comparison to the untreated check. Exceptions were Rubigan 50 W at 0.25 oz, applied curatively at a
14-day interval (until late July, when this treatment became effective), and Chipco 26019 WDG at 1.5 oz
and a 14-day schedule on June 25. S 6044 gave the plots an enhanced green color on July 5 and 21.

50

1

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52

Evaluation of Fungicides for Control of
Leaf Spot in ‘Park’ Bluegrass - 1994
M. L. Gleason
Trials were conducted at the Turfgrass Research Area of Iowa State University's Horticulture Research
Farm, Gilbert, IA. Fungicides were applied to ’Park’ Kentucky bluegrass maintained at 2 Vi-inch cutting
height, using a modified bicycle sprayer at 30 psi and a dilution rate of 5 gal/1000 fit2. The experimental
design was a randomized complete block with four replications. All plots measured 4 fit x 5 fit. To
stimulate disease development, the plot was irrigated for 15 min at 2 am, five nights per week, from June
7 through mid-July.
Fungicide applications began on June 7 and continued at recommended intervals on June 21, July 5 and
19, and Aug 2.
Disease development was very light during the test period. Although results indicated statistically
significant differences in disease control, interpretation of these differences is questionable due to the
lack of substantial disease pressure.

53

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54

Percolation Depth and Persistence o f
Soil under Various Application and Irrigation Regimes

in

T. Michaels
Bacillus thuringiensis japonensis (Btj) is a strain of Bt bacterium discovered in Japan in 1991 that is lethal
to white grubs. Btj must be eaten by a grub to be toxic. Btj will control larvae of the Japanese beetle
Popillia japónica, masked chafers Cyclocephala spp., and the green June beetle, Cotinis spp. It will be a
bioinsecticide product named M-PressTM by 1998. This study was funded by Mycogen Corporation, San
Diego, CA and is part of commercial development efforts to optimize M-PressTM.
The purpose of this study was to determine how three application volumes of 465, 930, and 1860
liters/hectare (corresponding to 50, 100, and 200 gallons/acre) and three immediate post-treatment
irrigation volumes of 0, 1, and 2 cm would affect the percolation depth of M-PressTM. The study was
performed on the USGA bentgrass green at the ISU Horticulture Farm which has soil of approximately
80% sand, 10% peat and 10% native loam. The intent was to gather information on which spray volume
and irrigation regimin with a fixed number of Btj spores (2.5 x 108 spores per cm) would deliver the most
bioinsecticide to the depth of 0-5 cm where white grubs feed. Treatments were set up in a randomized
complete block design with four replicates. Two randomly assigned soil cores samples were taken to a
depth of 11 cm from each 122 x 88-cm treatment plot. The cores were sectioned at increments of 0-1 cm
(thatch), 1-3 cm, 3-5 cm, 5-7 cm, 7-9 cm, and 9-11 cm, pooled, and placed in a sterile whirlpac bag and
frozen at 4 degrees Celsius until analysis. The treatments were sampled on day 0, 1, 2, 4, 6, 14, 30, and 60
for the purposes of determining the persistence of the bioinsecticide. No rain or irrigation was applied to
the site until after day 6 of the study. The soil samples were plated on selective microbiological medium to
quantify the number of colony forming units (CFU's) per gram of soil. Also, a dot-blot immunoassay
system is being developed to monitor the persistence of the Btj toxin in the soil.
The data collection and analysis are not yet completed, and spore counts in soil can be highly variable.
Preliminary results of three replicates from day 6 are presented below. The one and two-cm post-treatment
irrigation (PTI) delivered a greater number of spores to the 1-3 cm and 9-11 cm depths than zero cm
post-treatment irrigation. Depth 9-11 cm had fewer spores recovered for each treatment than the 1-3 cm
depth.
Table 32. AVERAGE CFU'Sa/GRAM SOIL (X 1,000); DAY 6, Three Blocks
Treatment

Depth of Soil Sample

GPAb

PTIc(cm)

50

0

1,440

77

50

1

25,300

4,860

1-3 cm

9-11 cm

50

2

16,166

3,010

100

0

6,343

253

100

1

21,933

151

100

2

18,766

13,310

200

0

8,463

200

1
19,733
200
2
29,420
aCFU- colony forming units; bGPA-gallons per acre (spray volume); cPTI-post-treatment irrigation

203
1,090
3,103

Preliminary interpretation of the results show post-treatment irrigation to have more influence on the final
distribution of the spores in the soil than the initial application volume. Both post-treatment irrigation
regimens delivered more spores than zero post-treatment irrigation to the 1-3 cm depth where grubs would
likely feed.
55

Pythium Root Diseases and Disease Complexes
o f Creeping Bentgrass
C. F. Hodges and D. A. Campbell
The research literature and general textbooks on diseases of turfgrasses have made little distinction
between the pathogenicity of Pythium on primary roots (seedling roots) and on adventitious roots (roots
from nodes that support the plant for most of its life) of creeping bentgrass. Most studies have been
conducted on primary roots and it has seemingly been assumed that the lesions and rotting of primary
roots also occur on adventitious roots. The few studies that have evaluated pathogenicity of Pythium
species to adventitious roots of creeping bentgrass do not show the development of lesions and/or rotting.
The isolation of Pythium from brown and/or rotted roots has contributed to the assumption that these
symptoms of adventitious roots are due to Pythium infection. There is growing evidence, however, that
Pythium is not an efficient rotter of adventitious roots and that their presence in rotted roots may be the
result of their association with other organisms in a disease complex. Studies involving controlled
inoculations of adventitious roots in my laboratory and those of other researchers suggest that there are
two relatively distinct ways in which Pythium species attack adventitious roots of creeping bentgrass.
One form of attack is characterized by Pythium-'induczd root dysfunction and occurs during the
establishment of creeping bentgrass on high-sand content greens as young adventitious roots develop
from nodal regions of the shoot. The second form of attack occurs in mature stands (3 years old or older)
of creeping bentgrass turf in which the Pythium species may function in a complex with other weak rootinfecting pathogens that can result in browning and/or rotting of infected roots.
P y th iu m -h \& \ic td R o o t D y s fu n c tio n

Pythium-induced root dysfunction occurs primarily on old golf courses where greens have been
reconstructed with high-sand content mixes, and to a lesser extent on newly constructed high-sand
content golf greens. Creeping bentgrass established on renovated greens in late summer or fall is
successfully established and grows well during the mild periods of the following spring and early
summer. With the arrival of hot, humid weather, the turf shows chlorotic or wilted patches that die in a
random pattern without evidence of foliar pathogens. Examination of the root system reveals what
appears to be healthy white roots that are shorter than normal. No lesions or rot are present on the roots.
When such roots are incubated under laboratory conditions, Pythium arrhenomanes or P. aristosporum
grow from the root tips, and cortical cells within 6 to 12 h. Large areas of infected greens can be killed
within two weeks and cultural and chemical control methods have not proven effective for this disorder.
The primary characteristic of this disease is that it occurs the first growing season following
establishment of the turf. The disease may reoccur the next year, but with much reduced severity. By
the third year the disease is usually no longer present. If symptoms typical of root dysfunction occur on
a green for the first time two or more years after establishment, the symptoms are due to a disease other
than
Pythium-induced root dysfunction.
Inoculation of young, developing adventitious roots of creeping bentgrass with P. arrhenomanes or P.
aristosporum decreases total weight of plants to 16 and 32% of healthy plants, respectively.
Examination of roots 3 to 4 weeks after inoculation reveal Pythium hyphae in root hairs and in somewhat
swollen regions behind root tips. It seems that root hairs and root tips provide the primary sites for
infection. Roots examined 10 weeks after inoculation show extensive infection of the cortex. Some root
tips are devitalized and the roots may be slightly tan-colored compared to healthy roots, but there are no
visible lesions or rot. With time, the roots deteriorate (due to age and infection) and hyphae will then
penetrate the vascular cylinder.

56

Pythium Root Infection in Mature Stands of Creeping Bentgrass
For the purposes of this presentation, a mature stand of creeping bentgrass is one that is at least three
years old and is supported exclusively by adventitious roots. Pythium species are commonly found in
soils supporting mature stands of turfgrass and they are often associated with both healthy and diseased
adventitious roots. The fact that Pythium species are commonly isolated from turf soils and from
diseased crowns and roots showing browning and/or rotting does not establish that they are responsible
for the problems observed. Healthy plants must be reinoculated, and the disease reproduced before
responsibility can be established. When diseased roots of any turfgrass species are examined and
cultured in a laboratory the presence of any Pythium species is known very quickly because they will
appear on the culture plates long before any other fungal pathogen. This characteristic of Pythium
species can result in a hastily arrived at conclusion that the Pythium isolate is responsible for the disease
in question. It has been our experience, that if these same cultures are observed for a longer period of
time the diseased roots usually yield other minor root pathogens. The question of assigning responsibility
for the disease then becomes very complex.
The question of the pathogenicity of Pythium species to adventitious roots of older stands of creeping
bentgrass remains unclear. Over the last several years, numerous species of Pythium have been
collected from the brown and/or rotted adventitious roots of mature stands of creeping bentgrass
displaying symptoms of wilt, chlorosis, nondescript thinning, and irregular patches of dead turf. Many
of the isolates are not capable of infecting healthy roots. Of the isolates that infected adventitious roots,
six reduced plant dry weight 42 to 81% of healthy plants only at high temperatures (95°F day/75°F
night), three reduced weight 49% to 75% only at low temperatures (75 °F day/55°F night), and seven
reduced weight at both high and low temperatures (high temperatures 67 to 84%, low temperatures 35 to
60%).
In all our observations, Pythium species behave as minor root pathogens with infection restricted to root
tips and hairs, and cortical tissues without penetration of the vascular cylinder. Roots are typically
shortened and are white to light tan. The symptoms produced in controlled studies are relatively mild
and have not resulted in the death of any plants. However, the more severe reduction in growth (30 to 40
percentile range of healthy plants) caused by some isolates could feasibility result in substantial damage
or death of plants under the stress of field conditions. Conversely, those isolates that result in mild
reductions in growth (70 to 80 percentile range of healthy plants) might have no effect or result in turf
with low vigor and/or thinning when subjected to field stress, but they may not be responsible for direct
killing of turf.
P y th iu m a n d D isease C o m p le x e s o f A d v e n titio u s R o o ts o f C re e p in g B e n tg ra s s

Pythium species isolated from diseased adventitious roots of mature stands of creeping bentgrass are
commonly associated with other minor root pathogens. In controlled studies, inoculation of adventitious
roots of creeping bentgrass results in a decrease in total weight of the plant and some degree of root
tanning, but it does not result in the severe root rot or plant death that is sometimes observed in the field.
This suggests that the Pythium species isolated from severely diseased adventitious roots of mature
stands of creeping bentgrass in the field may not be the sole cause of the disease. None of our
observations to date provide evidence that Pythium species are major pathogens (capable of producing all
field symptoms independently) of adventitious roots of mature stands of creeping bentgrass. If these
observations are representative, then it is probable that the Pythium species associated with severe rot of
adventitious roots are functioning as part of a root disease complex involving other minor root
pathogens.
Two groups of fungal organisms have been found associated with
infected roots. The first
group includes species of Curvularia, Fusarium, Bipolaris, Drechslera, and Rhizoctonia, all of which are
57

typically found with Pythium in the upper 2 cm of the sand. Most of these organisms seem associated
with the nodal regions of the stolons and extend into the upper part of the root system. The second group
of fungal organisms includes Acremonium (Cephalosporium), Microdochium (Idriela), Polymyxa, and
genera that typically produce ectotrophic hyphae. These various associations are most common on
adventitious roots collected from high-sand content greens. Preliminary (unpublished) adventitious root
inoculation studies with C. lunata, C. geniculata, M. bolleyi, and Acremonium species reveal that most
will infect the roots and that they, like the Pythium species, behave like minor pathogens in that they
colonize root tips, root hairs, and cortical tissue. Like the Pythium species, these organisms reduce the
dry weight of the infected plants, but also fail to kill plants in controlled studies. Curvularia lunata and
C. geniculata reduce the dry weight of creeping bentgrass in a range of 48 to 76% and 42 to 79% of
healthy plants, respectively. Isolates of M. bolleyi and Acremonium sp. reduce the weight in a range of
56 to 93% and 59 to 95% of healthy plants, respectively. It is probable that one or more of these
organisms in combination with Pythium could produce a disease complex that results in brown and/or
rotted adventitious roots.

58

Fertilizer Trials and
Soil Studies

Kentucky Bluegrass Response to Fertilizers - 1994
B. R. Bingaman and N. E. Christians
Fertilizer formulations supplied by Lesco were tested with Sustane, Sustane + iron, Pursell Polyon,
Lesco Poly +, Toro Nuture, and Scott's Poly-S for effects on Kentucky bluegrass growth and quality
(Table 1). This study was conducted at the Iowa State University Horticulture Research Station north of
Ames, Iowa. The experimental plot of'Park' Kentucky bluegrass was maintained at a 2" mowing height.
The soil was a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with an organic matter content of
3.0%, a pH of 7.05, 8 ppm P, and 67 ppm K. This site was not fertilized prior to the beginning of this
test.
Individual experimental plots were 5 x 5 ft and there were 10 treatments including an untreated control.
The study was arranged in a randomized complete block design. Three replications were conducted and
there were 3 ft barrier rows between replications.
The fertilizer materials were applied at 0, 8, and 16 weeks at an annual rate of 3 lbs/1000 ft2 (Table 33).
All fertilizers were applied in the granular formulation using plastic lined cardboard cups with holes
punched into the lid. These shaker dispensers allowed for uniform material application throughout the
individual plots.
Initial application was made on June 15, 1994. Prior to application the experimental site was examined
and the turf was found to be quite uniform in color, density, and overall quality. It was sunny with a
temperature in the mid 80's and southwesterly winds that were gusty at times. Lesco fertilizer #9352 was
quite difficult to apply uniformly under these windy conditions because of the very small particle size.
The size and weight of the other products was adequate so that they could be spread evenly throughout
the individual plots.
The 8 week application was made under nearly ideal weather conditions on August 16. The temperatures
was in the mid 80's, the skies were mostly sunny, and there was only a slight breeze. This application
was delayed because of rainfall on August 10-12. The weather was quite favorable for application of the
16 week materials on October 4. It was mostly sunny, calm, with temperatures in the mid 60's.
Rainfall was sporadic for the duration of this study. Supplemental irrigation was used to provide
adequate moisture to maintain the grass in good growing condition.
Visual quality and fresh clipping weight data were taken weekly beginning June 21. Variations from the
weekly data collection were necessary to adjust for special events, application dates, and adverse weather
conditions. Visual quality assessments were based on color, density, and phytotoxicity and recorded
using a scale of 9 to 1 (9 = best, 6 = acceptable, and 1 = poorest quality). Mowing height for collecting
clippings was 2".
Data were analyzed with the Statistical Analysis System version 6.06 (SAS Institute, 1989) by using the
Analysis of Variance (ANOVA) to test the significance of the treatments on the visual quality and
clipping weights. Least significant difference (LSD) tests were used to compare means among the
treatments.
While numerical differences in both quality and clipping yield developed early in the season, many of
the weekly evaluations showed no significant differences before mid-August (Tables 34 to 37). In the
late summer and early fall, the differences were much more pronounced and most weekly evaluations
were significantly different.

59

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‘Clipping weights are fresh weights and mowing height is 2".
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Polymer Coated Urea Fertilizer Study - 1994
B. R. Bingaman and N. E. Christians
Polymer coated fertilizer materials with 60, 90, and 120 day duration (UHS 2002, 2003, and 2004) from
United Horticultural Supply were tested with Urea, Lesco Poly +, Blue chip methylene urea, and Polyon
for effects on Kentucky bluegrass growth and overall quality (Table 1). This study was conducted at the
Iowa State University Horticulture Research Station north of Ames, Iowa. An established Kentucky
bluegrass area was used as the experimental plot. The soil was a Nicollet (fine-loamy, mixed, mesic
Aquic Hapludoll) with an organic matter content of 3.3%, a pH of 6.9, 7 ppm P, and 76 ppm K. This site
was not fertilized prior to the beginning of this test.
Individual experimental plots were 5 x 5 ft and there were 17 treatments including an untreated control.
The study was arranged in a randomized complete block design. Three replications were conducted and
there were 3 ft barrier rows between replications.
All fertilizers were applied in the granular formulation using plastic lined cardboard cups with holes
punched into the lid. These shaker dispensers allowed for uniform material application throughout the
individual plots.
The fertilizer materials were applied 0, 8, 12, 16, and 24 weeks into the study at an annual rate of 4
lbs/1000 fit2 (Table 38). The initial application of all fertilizer materials was April 27, 1994. It was
cloudy with a temperature in the mid 50's and a light northwesterly breeze. Prior to application the
experimental site was examined and the turf was found to be quite uniform in color, density, and overall
quality except in the area covered by plots 1 and 2 of Replication 2. In this area the quality of the
bluegrass suggested that there was a carry over from past fertilizer studies.
The 8 week application was made on June 21 under nearly ideal weather conditions with temperatures in
the mid 80's, mostly sunny skies, and a slight breeze. The 12 week application was performed on July
18. It was mostly sunny, calm, and temperatures were in the upper 80's. On August 16 the 16 weeks
application was made under sunny skies, with light winds, and temperatures in the upper 70's. The 16
weeks application of the UHS #2004 materials was made on August 26. It was sunny, breezy, and
temperatures were in the upper 80’s. The final application (24 weeks) was made on October 17. It was
cloudy with a light mist and temperatures in the mid 60's (Table 38).
Rainfall was sporadic for the duration of this study. Supplemental irrigation was used to provide
adequate moisture to maintain the grass in good growing condition.
Visual quality and fresh clipping weight data were taken weekly beginning May 9 (Tables 39-42).
Variations from the weekly data collection were necessary to adjust for special events, sequential
application dates, and adverse weather conditions. Visual quality assessments were based on color,
density, and phytotoxicity and recorded using a scale of 9 to 1 (9 = best, 6 = acceptable, and 1 = poorest
quality). Mowing height for collecting clippings was 2".
Data were analyzed with the Statistical Analysis System version 6.06 (SAS Institute, 1989) by using the
Analysis of Variance (ANOVX) to test the significance of the treatments on the visual quality and
clipping weights. Least significant difference (LSD) tests were used to compare means among the
treatments.

63

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Natural Organic Rate Study - 1994
B. R. Bingaman and N. E. Christians
Natural organic fertilizer materials were tested for their effects on Kentucky bluegrass growth and
quality. Sustane, Country Club, and Milorganite were applied at 0.5 and 1.0 lbs/1000 ft2 on May 11, July
15 and August 30 for a total of 1.5 and 3.0 lbs/1000 fit2annually. This study was initiated in 1993 and
continued in 1994 at the Iowa State University Horticulture Research Station north of Ames, Iowa. The
experiment was conducted in a 'Bronco' Kentucky bluegrass area. The soil was a Nicollet (fine-loamy,
mixed, mesic Aquic Hapludoll) with an organic matter content of 3.3%, a pH of 6.9, 7 ppm P, and 76
ppm K.
Individual experimental plots were 5 x 5 ft and there were 7 treatments including an untreated control.
The study was arranged in a randomized complete block design. Three replications were conducted and
there were 2.5 ft barrier rows between replications.
All fertilizers were applied in the granular formulation using plastic lined cardboard cups with holes
punched into the lid. These shaker dispensers allowed for uniform material application to the individual
plots.
Rainfall was sporadic during the study. Supplemental irrigation was used to provide adequate moisture
to maintain the grass in good growing condition.
Visual quality data and fresh clippings were taken weekly beginning May 13. Deviations from this
schedule were necessary to adjust for adverse weather conditions, fertilizer applications, and special
events. In addition, data collection was delayed at various times to allow the grass to accumulate
sufficient growth for clipping collection.
Visual quality assessments were based on color, density, and phytotoxicity and recorded using a scale of
9 to 1 (9 = best, 6 = acceptable, and 1 = poorest quality). Mowing height for collecting clippings was 2".
The fresh clippings from a single mower strip for each plot were placed into paper sacks and dried at 67
C for 48 hours prior to weighing.
Data were analyzed with the Statistical Analysis System version 6.06 (SAS Institute, 1989) by using the
Analysis of Variance (ANOVA) to test the significance of the treatments on the visual quality and
clipping weights. Least significant difference (LSD) tests were used to compare means among the
treatments.
The materials produced a relatively uniform response through the season in both quality and clipping
yield. The Country Club material produced a very rapid initial response and maintained good color
through the season. The Sustane and Milorganite showed a slower initial release, but provided a high
uniform quality through most of the season.

69

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‘Visual quality values are based on a scale of 9 to 1 : 9=best quality, 6 =acceptable quality, and l=poorest quality.

Table 43. Visual quality1 of Kentucky bluegrass treated with natural organic nitrogen materials for the period from May 13 to July 12.

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NS = not significantly different at the 0.05 level.

Table 45. Clipping weights1 of Kentucky bluegrass treated with natural organic nitrogen materials for the period from May 13 to July 12.

CM

Natural Organic Source Study - 1994
B. R. Bingaman and N. E. Christians
Natural organic fertilizer materials were tested for their effects on Kentucky bluegrass growth and
quality. Blood meal, com gluten meal, leather meal, Sustane (composted turkey manure), and
Milorganite (activated sewage sludge) were selected for testing as natural organic nitrogen sources. This
study began in 1993 and continued in 1994 at the Iowa State University Horticulture Research Station
north of Ames, Iowa. The experiment was conducted in an area of'Midnight' Kentucky bluegrass
established in 1993. The soil was a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with an organic
matter content of 3.6%, a pH of 7.4, 11 ppm P, and 88 ppm K.
Individual experimental plots were 5 x 5 ft and there were 6 treatments including an untreated control.
The study was arranged in a randomized complete block design. Three replications were conducted and
there were 2.5 ft barrier rows between replications.
Fertilizer materials were applied during the growing season at 3.0 lbs N/1000 ft2/yr. One lb N
applications were made on May 4, July 15, and August 30. All fertilizers were applied in the granular
formulation using plastic lined cardboard cups with holes punched into the lid. These shaker dispensers
allowed for uniform material application to the individual plots.
Rainfall was sporadic during this study. Supplemental irrigation was used to provide adequate moisture
to maintain the grass in good growing condition.
Visual quality data and fresh clippings were taken weekly beginning May 13. Deviations from this
schedule were necessary to adjust for adverse weather conditions, fertilizer applications, and special
events. In addition, data collection was delayed at various times to allow the grass to accumulate
sufficient growth for clipping collection.
Visual quality assessments were based on color, density, and uniformity and recorded using a scale of 9
to 1 (9 = best, 6 = acceptable, and 1 = poorest quality). Mowing height for collecting clippings was 2".
Fresh clippings from a single mower strip for each plot were placed into paper sacks and dried at 67°C
for 48 hours prior to weighing.
Data were analyzed with the Statistical Analysis System version 6.06 (SAS Institute, 1989) by using the
Analysis of Variance (ANOVA) to test the significance of the treatments on the visual quality and
clipping weights. Least significant difference (LSD) tests were used to compare means among the
treatments.
Each of the natural organic materials produced acceptable quality throughout the growing season (Table
47 and 48). Quality of leather meal treated plots dropped late in the season. Response to this material
still produced better quality than the untreated control.
Clipping response was similar to quality response through the growing season for nitrogen sources.
Lower turf quality was associated with lower clipping yields for leather meal (Table 49 and 50).

72

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Table 47.

Visual quality1o f Kentucky bluegrass treated with natural organic nitrogen materials for the period from May 13 to July 12.

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Clipping weights are expressed as grams dry weight.
NS = not significantly different at the 0.05 level.

Clipping dry weights(g) of Kentucky bluegrass treated with natural organic nitrogen materials for the period from May 13 to July 12.

o

Environmental
Research

TheUse o f a Natural Product for the
Preemergence Control of Annual Weeds
N. E. Christians
In 1985, it was observed that unprocessed com meal applied in large quantities to soil areas had an
inhibitory effect on the establishment of germinating plants. Further evaluations showed that there was
a naturally occurring, organic compound (or compounds) within the corn meal that had a growth
regulating effect on the root system of germinating plants. Studies were conducted to determine if any
corn meal components contained higher concentrations of the inhibitory substance. It was discovered
that high levels of inhibitor were found in corn gluten meal, the protein fraction of com grain.
Corn gluten meal contains 10% nitrogen by weight and was shown to be a good natural source of
fertilizer nitrogen for mature plants that had well established root systems. Further studies
demonstrated that corn gluten meal could be used as a natural “weed and feed” material for lawn areas.
Nitrogen in the product serves as a nutrient source to improve lawn quality, while the inhibitory
substance acts to prevent germinating weeds, such as crabgrass, from infesting the lawn. Several
grassy and broadleaf weeds have been shown to be controlled by preemergence application of com
gluten meal. United States patent 5,030,268 was issued for use of com gluten meal as a natural
preemergence herbicide in July, 1991 and reissued with broader claims as Re. 34,594 on
April 26, 1994. A marketing agreement has been reached with Gardens Alive Corporation of
Lawrenceburg, Indiana. They registered the product with the Environmental Protection Agency (EPA)
under the EPA Registration No. 56872-1 and EPA Est. No. 56872-IN-l in late summer of 1994.
Marketing began in the fall of 1994 under the name A-MAIZING LAWN.
Corn gluten meal is a byproduct of the wet-milling process. It has been used for decades as an animal
feed for dogs, poultry, fish, and many other animal species. The product is being promoted as an
environmentally safe, natural herbicide that can be used to control weeds preemergently in turf areas
without the use of synthetic preemergence herbicides that are presently used in large quantities in the
U.S.
Work has also been conducted on other crop systems, such as strawberries, floral crops, and vegetable
crops. It is anticipated that com gluten meal will find a market for these crop systems as well as for
home gardening.
The objectives of the following study were to observe the effects of com gluten meal on weed control
and turf quality of Parade Kentucky bluegrass under field conditions. Com gluten meal was applied to
the same 5 ft x 5 ft plots at the research station during 1991, 1992, 1993 and 1994 at levels of 0, 2, 4,
6, 8, 10, and 12 lb N/1000 ft2 (0, 20, 40, 60, 80, 100, 120 lbs com gluten meal/1000 ft2). Application
dates were April 22 in 1991, April 28 in 1992, April 26 in 1993, and April 27 in 1994. Very high
rates were included to determine if com gluten meal has any detrimental effects on turf over extended
periods of use.
Table 51 includes data on crabgrass control over the 4 year period from 1991 to 1994 and data on
clover and dandelion control for 1994. In the first year of the study, the 2 lb N (20 lb CGM)/1000 ft2
rate reduced crabgrass by 58% and the 4 lb rate reduced infestation by 86%. Control improved to
85% at the 2 lb rate in 1992 and to 91% in the 1993 season. Crabgrass was nearly eliminated in plots
treated with CGM rates above 2 lb N/1000 ft2 in 1992 and 1993. The 1993 season was one of the
wettest seasons in history. Grass on the plots often became very long between mowing, resulting in
some turf thinning. Crabgrass control dropped to 70% at the 2 lb rate in the spring of 1994, although

75

«

it remained good at higher rates of application. No detrimental effect was observed at any time during
the 4-year period.
There is no postemergence effect of CGM on weeds, the effect is entirely preemergence. Little effect
was expected on the infestation of perennial broadleaf weeds was anticipated in the study. By the end
of 1994, however, there was a considerable difference in clover and dandelion infestation between
nontreated and treated plots. Over the 4 year period, clover and dandelion infestation in the area
surrounding the plots and in the control plots began to increase, whereas treated plots maintained very
low infestation levels (Table 51). Clover infestation was very uneven, with most of the clover in the
control of the first replication, resulting in no statistical significant differences among plots.
Numerically, plots treated with 2 lb N/1000 ft2 had 81% less clover than control plots. Areas receiving
higher levels of CGM had even less clover. Dandelion infestation was reduced by 71 % in plots treated
for 4 years with the 2 lb N rate of CGM. Plots treated with higher levels were almost completely clean
of dandelions. Control plots showed an average infestation of 16% cover of clover and had 14
dandelion plants in the 25 ft2 plots. The reduction in broadleaf weeds is likely due to a combination of
the CGM inhibiting germination of these species and the competition of the grass in the treated plots
with the competing weeds. Broadleaf infestation will be monitored in future years of the study.
The study continues and com gluten meal has been applied at the same rate and to the same plots in the
spring of 1995.

76

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77

Greenhouse Screening Study o f Eleven Corn Gluten Meal
Related Samples for Their Inhibitory Activity on the Germination o f Creeping
Bentgrass (Agrostis palustris )
D. L. Liu, D. Gardner and N. E. Christians
This study was initiated on Feburary 8, 1995 to compare the herbicidal activity of eleven samples from
Grain Processing Corporation, Muscatine, Iowa. Four inch plastic pots (Belden Plastics, St. Paul, MN)
were filled with Nicollet field soil to a surface of 54 cm2. Creeping bentgrass (
palustris Huds.)
was seeded at rate of 0.030 g per pot. The eleven samples used for this study are listed as follows:
Sample #
1
2
3
4
5
6
7
8
9
10
11

Description
Thick gluten residue # 1
Thick gluten residue #2
Thick gluten overs # 1
ISU EXP #1
Hydrolyzed gluten
Hydrolyzed gluten residue
Hydrolyzed gluten overs
Spent carbon
Carbon treated filtrate
Adsorption resin eluate
ISU EXP #2

Samples #1, 2, 3 and 4 are experiment materials derived from com gluten meal. Each of the 11 samples
was applied to the surface of the seeded pots at the rates of 0, 1.0, 2.0, 4.0, 6.0, and 8.0 g/dm2. The
experimental design was a randomized block with three replicates for each treatment. The total of 198
pots were placed on a mist bench where constant moisture was supplied for one week. The pots were
then moved to a conventional greenhouse bench and were watered every day. Five days before the final
data were taken, all pots were subjected to a water stress period. Data on the percent coverage of plants,
number of plants, fresh clipping weight, and the average root length were taken four weeks after the
application.
The effects of the 11 samples on the germination of creeping bentgrass were expressed in four
parameters: the pecentage of live plant coverage, the number of live plants, average root length, and
fresh clipping weight in each pot. Data were analyzed by using the General Linear Models Procedure in
SAS System (6.07 version). The F-test indicated that treatments due to samples, rates, and interaction
between samples and rates were significantly different for all four variables at the 0.01 level.
Plant survival four weeks after seeding was expressed as the percentage of live plant coverage (Table 52)
and the number of live plants in each pot (Table 53). At the rates of 4 g/dm2 and above, most of the
samples except #3, #6, and #8 had more than 50% reduction in plant coverage as shown in Table 52.
Sample #5 completely inhibited plant germination at the rates of 6 g/dm2 and above. Table 53 shows that
most samples except #3 and #8 at the rates of 4 g/dm2 and above had less than 50% plant survival
compared to the control. Both Table 52 and Table 53 show that with sample #5 there was no plant
survival at rates of 6 g/dm2 and above.

78

The examination of root length gave the details of plant survival and the results are shown in Table 54.
It was demonstrated that all samples except #3 and #8 had less than 50% root growth compared to the
control at rates of 6 g/dm2 and above. Sample #5 was the most effective of the 11 samples, which
completely inhibited root development at rates higher than 6 g/dm2, followed by samples #4, and #11.
Table 55 shows that all samples except #7 and #8 had less than 50% shoot growth compared to the
control and sample #5 had no shoot growth which resulted in no fresh clippings at rates of 6 g/dm2 and
above.
From the results for all four variables, sample #5 (hydrolyzed gluten) was the most effective sample in
inhibiting grass germination and root development, followed by samples #4 (ISU EXP #1) and #11 (ISU
EXP #2). Samples #7 and #8 were the least effective of the samples tested.
Table 52. The effect of the eleven samples on the germination of creeping bentgrass. Data expressed as the percent of plant
survival is refered to the percentage of live plant coverage in each pot compared to the control.
Sample

______________ Percentage of Live Plant Coverage Per Pot (%)♦

#

1 g/dm2

2 g/dm2

4 g/dm2

6 g/dm2

8 g/dm2

1

98

68

32

2

0

2

93

85

27

5

0

3

105

98

88

8

0

4

100

83

12

7

1

5

100

92

10

0

0

6

110

98

68

8

0

7

108

100

44

40

8

8

103

90

82

53

55

9

107

90

32

8

18

10

107

68

18

0

5

11

120

110

2

8

2

♦Data were taken four weeks after the treatments. Each number is the average of the measurements of 3
replicates (n=3). The control which did not receive any sample is considered having 100% coverage (n=l 1).
The LSD(0 05)= 24%.

Table 53. The effect of the eleven samples on the germination of creeping bentgrass. Data were expressed as the number
of live plants in each pot.
Sample

__________________ Number of Live Plants Per Pot*

#

1 g/dm2

2 g/dm2

4 g/dm2

6 g/dm2

8 g/dnr

1

85

69

27

3

0

2

92

81

33

9

0
0

3

96

85

63

9

4

92

72

14

6

2

0

0

5

89

76

6

6

89

75

32

3

0

7

89

84

38

36

12

8

93

87

79

71

54

9

96

76

29

10

14

10

96

69

18

0

3

91
3
95
10
3
11
♦Data were taken four weeks after the treatments. Each number is the average of the measurements of 3
replicates (n=3). The control had average of 88 plants (n=l 1). The LSD(005)= 21.

79

Table 54.

The effect of the eleven samples on the germination of creeping bentgrass. Data were expressed as the average
root length which was the mean of 3 plants in each p ot.
Sample
#

Average Root Length Per Pot (mm)#
1 g/dm2

4 g/dm2

2 g/dm2

6 g/dm2

8 g/dm2

1

64

57

25

0

0

2

71

57

41

3

0

3

65

56

59

12

0

4

72

65

16

0

0

5

65

59

0

0

0

6

71

70

32

4

0

7

68

60

22

18

2

8

73

74

71

77

66

9

67

69

22

0

0

10

76

57

5

0

1

63
64
1
18
1
♦Data were taken four weeks after the treatments. Each number is the average of the measurements of 3
replicates (n=9). The control had 77 mm (n=l 1). The LSD(005)= 19 mm.
11

Table 55.

The effect of the eleven samples on the germination of creeping bentgrass. Data expressed as the fresh clipping
weight in each pot were taken four weeks after the treatments.
Sample

Fresh Clipping Weight (mg)

#

1 g/dm2

2 g/dm2

4 g/dm2

1

425

269

94

17

0

2

399

258

69

36

0

6 g/dm2

8 g/dm2

3

547

511

390

55

0

4

587

458

80

44

0

5

450

465

17

0

0

6

699

464

307

9

0

7

661

537

285

229

37

8

325

279

387

175

122

9

503

436

116

14

21

10

760

377

212

0.

25

717
544
11
12
79
11
♦Data were taken four weeks after the treatments. Each number is the average of the measurements of 3
replicates (n=3). The control had 262 mg (n=l 1). The LSD(003)= 206 mg.

80

Field Study o f Corn Gluten Meal and Corn Gluten Hydrolysate
for Crabgrass Control
D. L. Liu, B. R. Bingaman, and N. E. Christians
The weed control activity of com gluten hydrolysate has been demonstrated in petri dish and greenhouse
bioassays and proved to be more effective than that of com gluten meal. Hydrolysate was not available
in sufficient quantities for field work until 1994. A field study was initiated on April 29, 1994 at Iowa
State University Research Station to evaluate com gluten meal, and two com gluten hydrolysate
materials (CGH-A and CGH-B) for crabgrass control. CGH-A was prepared by treating an aqueous
slurry of com gluten meal with amylases, followed by filtration to remove the solubilized carbohydrates.
CGH-B was prepared by a simplified procedure which did not include amylase in the treatment.
The experiment was conducted in an area of Indigo Kentucky bluegrass plot and arranged in a
randomized complete block. The individual plots were 1 ft. by 1 ft. with 3 replications. The small plot
size was necessary because of the limited availability of the hydrolysate. Crabgrass was seeded in the
experimental area before the application of treatments. The three samples were applied at rates of 0, 5,
10, 20, 30, and 40 lbs materials per 1000 ft2(Table 56).
Visual turf quality data were taken weekly for 10 weeks (Table 57). The degree of crabgrass control was
asessed by counting the number of crabgrass plants per individual plot weekly beginning on July and
continuing for 3 weeks (Table 58).
The results on percent of crabgrass reduction demonstrate that com gluten hydrolysate was more
effective in crabgrass control than com gluten meal (Table 58). In general, CGH-B was less effective
than CGH-A in crabgrass control. However, a great variation in crabgrass germination among the
replications was observed. This same trial is being repeated on the same area in 1995 by Jason Gates, an
undergraduate honors student who is performing his work under the direction of Dr. Liu.
Table 56. Granular com gluten meal and com gluten hydrolysate treatments.
Treatment*
Sample
1. Untreated Control

Rate
(lb /1 0 0 0 ft2)

gram /plot

ml H20/Plot

NA

NA

NA

2 . Granular CGM

5

2.268

NA

4.536

NA
NA

3. Granular CGM

10

4. Granular CGM

20

9.072

5. Granular CGM

30

13.608

AA

6 . Granular CGM

40

18.144

NA
150

7. Gluten Hydrolysate A

5

2.268

8 . Gluten Hydrolysate A

10

4.536

150

9. Gluten Hydrolysate A

20

9.072

150

10 . Gluten Hydrolysate A

30

13.608

150

11 . Gluten Hydrolysate A

40

18.144

150

12 . Gluten Hydrolysate B

5

2.268

150

13. Gluten Hydrolysate B

10

4.536

150

14. Gluten Hydrolysate B

20

9.072

150

15. Gluten Hydrolysate B

30

13.608

150

16. Gluten Hydrolysate B
40
18.144
'Treatments 2-6 were applied as granular materials. Treatments 7-16 were applied as liquids.

15

81

Table 57. The effect of com gluten meal (CGM) and two com gluten hydrolysates (CGH-A and CGH-B) on Kentucky bluegrass
quality*.
_____________________________ Turf Quality**______________
Treatment

________________ Number of Weeks After Treatment Application
Rate

Sample

lb/ 1000 ft2

3

4

5

6

7

8

9

10

11

12

Control

0

8

7

6

7

7

6

7

7

7

6

5

9

7

7

7

7

7

7

8

7

7

10

9

7

7

7

7

7

8

7

7

7

20

8

7

7

8

8

7

7

8

8

8

CGM

30

9

8

8

8

9

8

9

8

8

8

40

8

8

8

9

9

9

__9

9

9

9

5

8

7

7

7

7

6

7

7

8

7

CGH-A

10

9

8

7

8

8

7

7

7

8

7

20

9

7

8

8

7

8

8

8

8

8

30

9

9

9

8

8

8

8

8

8

8

40

_9__

8

9

8

8

8

9

5

8

7

7

7

7

7

7

7

8

7
7

CGH-B

__8 __ __9 _

8

10

9

7

7

7

7

7

7

7

7

20

9

8

7

7

8

7

8

8

8

8

30

9

8

8

8

8

8

8

7

8

8

40

9

9

8

8

8

8

8

8

9

8

1

1

1

1

1

1
1
1
1
1
ISProo-M_________
♦Plots were evaluated on a 1-9 scale, 9= best quality, 6 = acceptable quality, and 1= dead turf.

**Values are means of scores of 3 replicates compared against control.

Table 58. The effect of com gluten meal (CGM) and two com gluten hydrolysates (CGH-A and CGH-B) on crabgrass control in
Kentucky bluegrass field plots.
Percent of Crabgrass Reduction (%)♦

Treatment
Sample
CGM

CGH-A

CGH-B

Rate
(lb/ 1000 ft2)

Rate (g/m2)

Week 12

Week 14

Week 16

5

24.4

30

25

18

10

48.8

68

65

60

20

97.7

38

30

53

30

146.5

30

70

70

40

195.9

87

70

83

5

24.4

57

35

53

10

48.8

76

60

60

20

97.7

87

83

77

30

146.5

87

83

83

40

195.9

81

83

83
25

5

24.4

25

30

10

48.8

81

77

70

20

97.7

87

83

77

30

146.5

81

77

65

40

195.9

68

65

70

30

28

LSD(005)
36
♦Values are means of 3 replicates as compared with the untreated control.

82

Determining Effective Rates of Different Products of
Corn Gluten Meal For Weed Control
J. T. Gates, D. L. Liu, and N. E. Christians
With pesticides constantly coming under close public scrutiny, a shift can be noted from synthetic to
natural organic pesticides. Com gluten meal, a byproduct of the wet milling process, has been found to
possess root inhibiting activity on grass and broadleaf species. Com gluten meal can be made into a
pelletized form for easy application on a turfgrass area. Along with its ability to provide herbicidal
activity it has an analysis of 10% nitrogen. While com gluten meal is relatively insoluble in water, a
enzymatically hydrolyzed com gluten meal is quite water soluble. This water soluble com gluten
hydrolysate product would allow for easier application and a possibly more active herbicide. In this
study, we looked at different rates of four com gluten meal products and four hydrolysate products. The
objective of this study was to compare the herbicidal activity of these different com gluten meal related
products in the greenhouse.
The four sampes of com gluten meal and four samples of com gluten hydrolysate used in this study are
listed in Table 59. Four inch pots (Belden Plastics, St. Paul, MN) were filled with Nicollet soil to the
surface of 54 cm2. The soil was sifted for consistency and placed into the pots. Creeping Bentgrass
)P
(.Agrostis
alustri was sewed on the soil at a rate of 5 g/1000ft2 (0.029 g/pot). On April 6, 1995 each of
the eight materials were applied as a dry application to the surface of the soil at the rates of 0, 0.5, 1, 2, 3
g/dm2, which is equal to 0, 10, 20, 40, and 60 lbs./l 000ft2. The total of 102 pots were then placed on a
mist bed for one week to provide ample moisture for germination. After germination was complete, the
pots were moved to a bench where they were hand watered twice a day. This study was arranged as a
randomized block design with 3 replications. Initial data on percent cover and plant number per pot were
taken two weeks after the application. Three weeks after the initiation of the study, all pots were allowed
to dry for five days before the final data were taken. The data were analyzed by using the General Linear
Models Procedure in the SAS system (6.07 version).
The preliminary data that were taken at week two, had already begun to show reductions in percent cover
and plant number. While there was a significant difference in data, effects were not as dramatic as week
three data, which are presented in this report, after the plants had experienced water stress.
Week three data were taken on percent cover, plant number, clipping weight and root length. The
averages of all three replicates are presented as percent reductions from the control in Tables 59, 60, 61,
and 62, respectively.
To determine plant survival rate, percent cover (Table 59) and number of live plants per pot (Table 61)
were asessed. Both of these parameters show little reduction at the two lower rates and large reductions
at the two higher rates. Clipping weights were measured to determine how healthy the plants were.
More growth is seen in the first two rates in response to the nitrogen in the materials, while the higher
rates suppressed the growth (Table 62).
Since the com gluten meal products have the greatest affect on the root system, the root lengths were
taken to see if they had been suppressed by the products. Within this parameter, a reduction at higher
rates and larger differences between products were observed. The higher rates of each product had
greater root suppression than the lower rates. The hydrolaste products had a larger affect on the root
system than the com gluten meal products had at the same rate. The greatest reduction was seen in the
product GH1 (Table 63).

83

With little doubt one can see the effects com gluten meal products have on the plant. It has in most cases
reduced the quality of the plant, and caused a reduction in the number of plants that have survived. In
some cases the data contradict this general assumption. The percentage cover and clipping weight will
almost always decrease with higher application rates. In some of the lower application rates an increase
is seen in plant cover and clipping weight (Tables 60 and 62). This is due to a nitrogen response. These
treatments were not at lethal rates in the greenhouse conditions and the plants that lived were able to
increase growth from the nitrogen present in the products.
Consideration must also be given to the weather conditions at the time. A five day dry down has given
ample time to show stress in earlier greenhouse studies. During the dry down period in this study, it was
cloudy and by the time of termination for the study some pots still had ample moisture for plants to
survive. This allowed for plants with very small root systems to survive where death would have
occurred with drier soil conditions. Root data confirm that rooting was reduced by the treatments (Table
63). For each product, there is an evident decrease in the plants root system. In an established turfgrass
environment these plants will have difficulty in competing with healthy plants with established root
systems. The root data in this study gives the primary evidence that the hydrolosate forms are more
effective then the com gluten meal products. In particular GH1 suppressed root growth dramatically
(Table 63).
Table 59. List of eight samples used in this study.
Sample
GM1
GM2
GM3
GM4
GH1
GH2
GH3
GH4

Description
Grain Processing Corporation (GPC)1995 Com Gluten Meal
GPC Thick gluten residue # 1
GPC Thick gluten residue #2
Gardens Alive! Com Gluten Meal
GPC 1995 Com Gluten Hydrolysate
GPC Com Gluten Hydrolysate (CGH-A)
GPC Com Gluten Hydrolysate (CGH-B)
Sigma Chemical Company Com Gluten Hydrolysate

Table 60. The effect on the plant coverage of the creeping bentgrass. Data are expressed as percent reduction from the control.
Percent Reduction in Plant Coverage Per Pot* (%)
Sample

0.5 g/dm2

CGM1

6

CGM2 ‘

1

CGM3

29

CGM4
CGH1

1.0 g/dm2

2.0 g/dm2

3.0 g/dm2

14

42

65

14

73

70

17

67

88

36

46

44

42

7

17

61

70

CGH2

26

4

48

55

CGH3

16

29

67

95

CGH4
17
14
54
83
♦Data were taken three weeks after treatments. Each number is the average percent cover over the 3 replicates (n=3) expressed
as percent reduction. The control which did not receive any treatment is considered having 100% coverage (n=6 ). The
LSD(0.05)= 37%.

84

Table 61. The effect of the samples on the germination of creeping bentgrass. Data are expressed as percent reduction from the
control.
Percent Reduction of Live Plants Per Pot* (%)
Sample

0.5 g/dm2

1.0 g/dm2

2.0 g/dm2

3.0 g/dm2
75

CGM1

33

39

60

CGM2

29

39

81

78

CGM3

50

41

76

91

CGM4

55

62

60

59

CGH1

21

41

72

78

CGH2

47

32

63

68

50
76
96
40
CGH3
89
83
89
CGH4
88
♦Data were taken three weeks after treatments. Each number is the average number of live plants per pot over the 3 replicates
(n=3) expressed as percent reduction. The control which did not receive any treatment is considered having 100% of plant
number (n=6). The LSD(0.05)= 34%.

Table 62.

The effect of the samples on the growth of the germinating creeping bentgrass. Data are expressed as percent
reduction from the control.
Percent Reduction in Fresh Clipping Weight Per Pot* (%)

Sample

0.5 g/dm2

CGM1

-3

1.0 g/dm2
-8

2.0 g/dm2

3.0 g/dm2

47

79

68

CGM2

-39

-38

71

CGM3

-12

-36

57

85

CGM4

-5

5

46

42

CGH1

-25

-87

52

79

CGH2

-40

-95

3

73

CGH3

-10

-35

13

84

15
-62
CGH4
66
-35
♦Data were taken three weeks after treatments. Each number is the average fresh clipping weight over the 3 replicates (n=3)
expressed as percent reduction. The control which did not receive any treatment is considered having 100% clipping weight
(n=6). The LSD(0.05)= 35%.

Table 63.

The effect of the samples on the root formation of germinating creeping bentgrass. Data are expressed as percent
reduction from the control.

2.0 g/dm2

3.0 g/dm2

42

56

71

30

58

70

23

36

00

Percent Reduction in Root Length Per Pot* (%)

79

20

41

55

47

80

92

CGH2

21
11
20

30

65

89

CGH3

27

30

48

85

Sample

0.5 g/dm2

1.0 g/dm2

CGM1
CGM2

12
0

CGM3
CGM4
CGH1

68
86
CGH4
15
52
♦Data were taken three weeks after treatments. Each number is the average root length over the 3 replicates (n=3) expressed as
percent reduction. The control which did not receive any treatment is considered having 100% of root length (n=6). The
LSD(0.05)= 21%.

85

The Use o f Corn Gluten Meal Hydrolysate as a
Natural Product for Weed Control
D. L. Liu, N. E. Christians, and J. T. Garbutt
Some natural plant compounds inhibit growth and development of other plants and may function as
herbicides or serve as the starting point for chemical synthesis of biodegradable herbicides. These
materials are considered to represent an environmentally sound approach to weed control (Rice, 1984).
It has been reported that com gluten meal, which is a by-product of com from the wet milling process, is
useful as a natural preemergence herbicide and fertilizer for various plant production systems
(Christians, 1993). Com gluten meal is quite water-insoluble. This characteristic limits its use as an
herbicide for some applications. It is difficult to apply evenly; as a result, there is a risk that the soil on
which it is applied will not be completely covered, thereby reducing its effectiveness. Also, sprayable
herbicides are advantageous for application to certain crops (Liu et al., 1994). Therefore, a continuing
need exists for potent, natural preemergence herbicides that are also highly water dispersible and/or
water soluble. The objective of this study was to compare the bioactivity of com gluten meal and com
gluten hydrolysate in both petri dish and soil bioassays for weed control.
D e s c r ip tio n o f S a m p le s :

Com gluten meal is commercially available as a byproduct of com milling. It is made by drying the
liquid gluten stream separated from com during the com wet milling process. Conventionally, com
gluten is filtered and dried to produce solid com gluten meal, which is sold as an animal feed product. It
is typically composed of 60 to 70% protein (Dry Basis).
Com gluten hydrolysate may be prepared by a process that involves treating an aqueous slurry of com
gluten meal with proteases and amylases. The sample of gluten hydrolysate A (CGH-A) was prepared
by treating the proteinaceous slurry with amylases, followed by filtration to remove the solubilized
carbohydrates (Christians, 1994). The insoluble residue is then treated with one or more proteases to
solubilize the protein components. After pH adjustment with acid, the slurry is filtered and centrifued.
The effluent is dried in a conventional manner to yield CGH-A, which properties are listed in Table 64.
Com gluten hydrolysate B was prepared by a simplified procedure which did not include amylase in the
treatment but still yields a water-soluble form of lower protein content (about 70% protein, DB).
G r o w th C h a m b e r S tu d y :

A study was conducted in a controlled environment to investigate the effect of com gluten hydrolysate A
on creeping bentgrass and crabgrass. An aqueous dilution of the sample in 7 mL water was applied to a
blotter paper measuring 42.3 cm2 at levels of 0, 0.12, 0.24, 0.36, and 0.48 g/dm2. Eighteen seeds were
placed on the blotter papers which were then put into petri dishes, and placed into a controlled
environmental chamber. The chamber was set at a 16h photoperiod and maintained at a constant 25°C.
Table 65 illustrates the percentage of germination of the creeping bentgrass and crabgrass with varying
application levels of the com gluten hydrolysate A, which completely stopped germination of creeping
bentgrass at application levels above 0.24 g/dm2, and germination of crabgrass at application levels
above 0.12 g/dm2.
In the first greenhouse study, a comparison was made regrading the effects of com gluten meal and the
com gluten hydrolysate (CGM-A) on the establishment of perennial ryegras (
perenne L.).
Application levels of the dry hydrolysate to the surface of soil pots seeded with L. perenne ranged from 0
to 7.8 g/dm2. The pots were allowed to stay on the mist bench for a 24-hour period in order to moisten

86

the soil with leaching of the water soluble com gluten hydrolysate. Table 66 demonstrates the increased
effectiveness of the com gluten hydrolysate as compared with com gluten meal. Treatment with 5.2
g/dm2 of com gluten hydrolysate resulted in 97% control. The same level of com gluten meal, however,
resulted in only 3% control.
In the second greenhouse study, the effect of two com gluten hydrolysates materials (CGH-A and CGHB) on crabgrass was compared. The crabgrass was seeded at a rate of 0.19 g/dm2 onto 58 cm2 pots filled
with a clay loam soil. The hydrolysates were applied to the surface of the pots at levels of 0, 0.86, 1.72,
3.44, and 6.88 g/dm2. The pots were then placed on a mist bench for 6 days. After seed germination, the
pots were moved to a greenhouse bench and maintained for 15 days. Data were collected on the number
of live shoots from each pot. The study was repeated three times. Table 67 illustrates the results of this
study. The CGH-A reduced the establishment of crabgrass by 76%, 96%, 100%, and 100% at
application levels of 0.86, 1.72, 3.44, and 6.88 g/dm2, respectively. The CGH-B reduced the
establishment of crabgrass by 40%, 78%, 98%, and 100% at the same application levels. Thus, while
CGH-B is somewhat less effective than CGH-A, it is still highly active.
This invention provides a selective, non toxic preemergence herbicide for use on soil plots to control
weeds. Com gluten hydrolysate has been found to provide a water-soluble material which is more active
than com gluten meal as preemergence herbicide. It completely stopped root formation of test species at
an application level of 0.24 g/dm2 in controlled environmental chambers and prevented plant
establishment by 96% at a level of 1.72 g/dm2 in greenhouse trials on soil. The com gluten meal
hydrolysate can potentially be used as a natural herbicide. U.S. patent No. 5,290,749, entitled
"Preemergence weed control using plant protein hydrolysate" was issued on March 1, 1994. Com gluten
hydrolysate can be used as a growth-regulating material to inhibit root formation of germinating weeds
in agricultural settings, and thereby act as natural preemergence herbicides.
R e fe re n c e s :

Christians, N. E. 1993. The use of com gluten meal as a natural preemergence weed control in turf. In
Carrow, R. N., Christians, N. E., and Shearman, R. C. (eds) International Turfgrass Society Research
Journal. Intertec Publishing Corp., Overland Park, KS, pp 284-290
Christians, N. E., Garbutt, J. T, and Liu, D. L. 1994. Preemergence weed control using plant protein
hydrolysate. U.S. Patent Number 5,290,749
Liu, D. L., Christians, N. E., and Garbutt, J. T. 1994. Herbicidal activity of hydrolysed com gluten meal
on three grass species in controlled environments. Journal of Plant Growth Regulation Vol. 13 No. 4
pp221-226
Rice, E. L. 1984, Allelopathy (2nd ed.) Academic Press, New York.

Table 64. Properties of com gluten hydrolysate A (CGH-A).
Cream-tan powder
>90
>50
>90
>6.5
Soluble with slight haze
<5
Characteristic odor

Appearance
Dry substance, %
Solids recovery
Protein, % DB (% Kjeldahl nitrogen X 6.25)
pH (as 5% solution)
Water solubility (as 10% w/v solution)
Ash, % DB
Odor

87

Table 65. The effect o f com gluten hydrolysate on germination o f two grass species.

Percentage of Germination of Creeping Bentgrass and Crabgrass Treated
with Com Gluten Hydrolysate
Percent Germination (%)♦

Level of Hydrolysate
(g/dm2)
0.00
0.12
0.24
0.36
0.48
♦Values are means of scores of 3 replicates.

C. Bentgrass
61
44
11
0
0

Craberass
67
6
0
0
0

Table 66. The effect of com gluten meal (CGM) and com gluten hydrolysate A (C GH-A) on the establishment of perennial
ryegrass on soil in the greenhouse.
Application Level of
CGM and CGH-A
(g/dm2)

Percent of Inhibition (%)♦
------------------------------------------------------------------------CGM
*

0.0
1.3
2.6
3.9
5.2
6.4
7.8
♦Values are means of scores of 3 replicates.

0
0
0
0
3
0
10

CGH-A
0
0
60
87
97
100
97

Table67 4. The effect of two com gluten hydrolysates on the establishment of crabgrass seedling on soil in the greenhouse.
Crabgrass (% cover/pot)*

Level of Hydrolysate
(g/dm2)

9s

oo
00

0.00
0.86
1.72
3.44

CGH-A

CGH-B

95
23
4
0
0

95
57
21
2
0

♦Values are means of scores of 3 replicates.

88

Bioactivity o f a Pentapeptide Isolatedfrom Corn Gluten Hydrolysate
on the Germination o f Perennial Ryegrass Seeds
D. L. Liu and N. E. Christians
It has been found that hydrolysed com gluten meal and 5 dipeptides, which could be isolated from com
gluten hydrolysate, have root-inhibiting activity and can be used as natural herbicides (1994 Iowa
Research Report, pp 84 and 85). Two patents, numbers 5,290,749 anf 5,290,757, were issued by the U.S.
Patent and Trademark Office on March 1, 1994 for use these products as preemergence weed control
materials. The objective of this study was to continue to isolate and identify more biological compounds
from com gluten hydrolysate for weed control. On May 8, 1994, another bioactive compound was
isolated from com gluten hydrolysate and identified to be a 5-residue peptide, Leu-Ser-Pro-Ala-Gln. The
inhibitory activity of the compound to germinating perennial ryegrass seeds is shown in Table 68. An
international patent application entitled “Preemergence weed control using natural herbicides” was
submitted in July of 1994.

Table 68. Bioactivity of Leu-Ser-Pro-Ala-Gln by using the perennial ryegrass petri dish bioassay*.
Pentapeptide
pg/cm2

Percentage of Control’*(%)
Root Length

Shoot Length

50.Ü16.9
13
14.5±3.2
26
44.2Ü7.6
15.5±2.7
27.7±7.1
39
11.6±2.7
52
10.2±9.1
13.5±4.4
104
0
0.5±1.3
* Each dish contained a Whatman No. 1 filter paper measuring 38.5 cm2 in area.
** Control had lmL deionized distilled water per plate and was considered as 100%. Values are means
of measurement of the length of 7 seedlings ± standard deviation.

89

Cellular Effects o f Root Inhibiting Compounds Derived
from Corn Gluten Meal
J. B. Unruh and N. E. Christians
In 1985, it was observed that unprocessed com meal applied in large quantities to soil areas had an
inhibitory effect on the establishment of germinating plants. Further studies showed that the protein
fraction of com grain, com gluten meal, had higher levels of the inhibitor. The work of D.L. Liu and
N.E. Christians, Iowa State University, subsequently led to the isolation and identification of five root
inhibitory compounds contained in the water soluble protein extract from com gluten meal. These
compounds were identified as the dipeptides alaninyl-asparagine, alaninyl-glutamine, glycinyl-alanine,
alaninyl-alanine, and glutaminyl-glutamine.
In an effort to better understand the efficacy of these root inhibiting dipeptides for weed control
purposes, investigations are currently underway to determine the effects these compounds have on
germinating perennial ryegrass seeds.
Microscopic studies focusing on cellular activity of treated and untreated plants are currently being done.
In addition to the structural and morphological observations, studies using a radioactive isotope of the
root inhibiting compound, alaninyl-alanine, are being conducted. This isotope is being used to trace the
compound’s movement through the seedling.
Results of these experiments show profound differences between treated and untreated seedlings. The
cellular effects of the root inhibiting compounds appear to be concentration dependent. At low treatment
levels, the cell structural integrity of the treated seedlings appears normal. At higher concentrations,
however, the cells are greatly disrupted and the cell walls and membranes are not intact. Furthermore,
the degree of severity is greatest on the perimeter of the root, and diminishes towards the cortex.
Autoradiographs of seedlings treated with a low concentration of radioactive alaninyl-alanine, show
uniform labeling throughout the root. As the level of treatment increases, the labeling intensifies and
localizes itself only in the outermost layers of cells. At the highest level of treatment, virtually no label
is noted on the interior of the root, and the damage appears to be a necrosis of the cells.
In addition to the structural and morphological differences between treated and untreated seedlings,
differences in cell processes have been observed. Mitosis, the process by which cells replicate, is
drastically altered. Differences in mitosis are seen regardless of the concentration of root inhibiting
compound. There also appears to be a peculiar substance between the cells and in vacuole-like structures
seen within the cells.
This project is nearing an end, and a comprehensive report detailing all the factors involving the cellular
effects of these root inhibiting compounds is being prepared.

90

Fate o f Nitrogen Applied to Turfgrass- Co vered Soil Columns
S. K. Starrett, N. E. Christians, and T. A. Austin
Current public concern for the environment has focused attention on the environmental effects of
chemical applications to turfgrass areas. Little research has been done concerning the environmental
effects of nitrogen (N) applied to turfgrasses. Our objectives were to investigate the hydrology of 50-cm
undisturbed soil columns with a Kentucky bluegrass turf intact macropores under a heavy (four 2.54-cm
applications) and a light regime (sixteen 0.64-cm applications), and to measure the fate of N, using l5N as
a tracer, when applied to an undisturbed soil column. Mean leachate values for columns under heavy
irrigation regime totaled about 6 times the amount collected from columns under the light irrigation
regime. We found that the heavy irrigation increased N that leached through the 50-cm undisturbed soil
columns by 30 times and decreased volatilization of liquid urea compared with the light irrigation.

Fate

o f ISN AmendedUrea in Turfgrass Biosystems
S. K. Starrett, N. E. Christians, and T. A. Austin

The fate of nitrogen (N) has been studied under several agronomic crops and agricultural profiles, but
relatively little information has been collected from areas managed as turfgrass. The turfgrass industry
has become the focus of environmental concerns in recent years and is often identified as a source of
ground water contaminate. The objectives of this study were to investigate the hydrology of (20-cm
pratensis
diameter by 50-cm depth) undisturbed soil columns covered with a Kentucky bluegrass (
L.) turf under a heavy (one 2.54-cm application) and a light (four 0.64-cm applications) irrigation
regime; and to quantify the fate of ,5N-labeled urea when it is applied to an undisturbed soil column
having intact macropores. Clipping, verdure, and thatch/mat samples were taken from each column, and
the soil was excavated in 10-cm layers at the end of the 7-day test period. A glass collection chamber
was used to collect volatilized N and a plastic bag for leachate collection. All samples were analyzed for
atom % l5N. Volatilization of N was negligible because irrigation was applied immediately after the
application of N. The heavy irrigation regime significantly increased the transport of N below 30-cm by
5 times, compared to the light irrigation regime. Eighty-five percent of the N found in the leachate from
the 50-cm columns was in the urea form indicating that macropores may have played a major role in
transport of surface applied N through the soil profile.

Comparing Chloride Transport in Undisturbed and Disturbed Soil
Columns Under Turfgrass Conditions
S. K. Starrett, S. E. Luke, N. E. Christians, and T. A. Austin
Transport of surface applied chloride in undisturbed soil columns with intact macropores was compared
to disturbed, repacked columns of the same soil. The total amount of chloride that leached from 20-cm
deep soil columns was 2.0 times higher for the undisturbed columns than for the disturbed columns.
Chloride (CL) recovered (mass basis) in layer #2 (6.7 to 13.4-cm) was 1.79 times higher and in layer #3
(13.4 to 20.0-cm) was 2.72 times higher for the disturbed soils than for the undisturbed. For the plant
and thatch layer (0.0 to 2.0-cm) the opposite was observed, total CL recovered from the undisturbed
columns was 2.4 times higher than the disturbed columns.

91

Cargill Particle Size Corn Gluten Meal Study - 1994
B. R. Bingaman and N. E. Christians
The objective of this study was to assess the efficacy of different com gluten meal products on the
survival of creeping bentgrass, Agrostis palustris Huds. Six samples of various particle mesh sizes were
supplied by Cargill and were compared with standard pelletized and nonpelletized (powdered) com
gluten meal produced by Grain Processing (Table 69).
Eight different com gluten meal material and an untreated control were screened. The Cargill products
had particle sizes of >20, <20, >10, 10-20, 20-40, and <40 mesh. The pelletized material from Grain
Processing was their standard product consisting of pellets of various sizes. Their nonpelletized material
was a very fine, dusty powder.
The materials were applied at 0.0, 0.353, 0.706, and 1.058 g/pot on the basis of weight of product per
surface area of the pots. These rates correspond with 0.0, 20.0, 40.0, and 60.0 lbs/1000 ft2, respectively.
The recommended rate for CGM is 20 - 40 lbs/1000 ft2.
All plants were grown under greenhouse conditions in #3, square, Lockwood green plastic pots with a
7.0 cm top diameter. The planting medium was sifted Nicollet (fine-loamy, mixed, mesic Aquic
Hapludoll). Bentgrass seeds were planted at a depth of 0.6 cm.
Soil surface preemergent (PRE) and preplant incorporated (PPI) application methods were used. For the
PRE treatments, the pots were filled with soil to the 0.6 cm from full line. The seeds were planted on
this surface and were covered with enough soil to fill the pots. The PRE materials were then spread
evenly on the soil surface. The PPI treatments were evenly mixed with the volume of soil sufficient to
fill the upper 2.5 cm of the pots. Three-quarters of this soil and com gluten meal mix was placed into the
pots and the seeds were planted on this surface. The remaining one-quarter of the mix was used to cover
the seeds. By using these methods the seeds in the PRE and PPI treated pots were planted at the same
depth.
Supplemental lighting from high-pressure sodium lamps was used to enhance the natural irradiance and
to extend the daylength to 16 hours. These lights delivered approximately 70 mmoles m'2 s'1of
irradiance.
To ensure maximum germination rates, the soil was kept moist for 14 days and was then allowed to dry
until the untreated control plants were wilting. Because com gluten meal inhibits the formation of roots
at the time of germination, the efficacy of the various materials was assessed at this time by evaluating
the response of treated plants to moisture stress. These plant stress data represent the number plants per
pot that were still green and presumed alive. All plants were then thoroughly watered and kept moist for
3 days. The number of he number of green, living plants per pot were again counted. These plant
survival data were taken to measure the ability of some plants to recover from severe moisture stress and
are another indication of the degree of root inhibition caused by the com gluten meal.
The lengths of the primary roots also were measured for Replication 1 to obtain a visual estimation of the
amount of root inhibition that was present. A representative plant in each pot was carefully extracted and
the soil was removed. The length of the longest root was taken and these measurements are included in.

92

Two sets of three replications were conducted using the same protocol and under the same growing
conditions. The first 3 replications were started on November 1 and ended on November 21. The second
set was begun on November 7 and terminated on November 29.
Data were analyzed with the Statistical Analysis System version 6.06 (SAS Institute, 1989) by using the
Analysis of Variance (ANOVA) to test the significance of the com gluten meal products and application
methods on bentgrass survival. Least significant difference (LSD) tests were used to compare means
among the treatments.

Table 69. Survival after a period of moisture stress of creeping bengtrass receiving soil incorporated (PPI) Cargill and Grain
Procesing com gluten meal materials.

lbs/1000 ft2

Mean Plant
Survival

Untreated control

0

126

>20 mesh CARGILL

20

72

43
73

Treatment

% Reduction in Plant
Survival
—

>20 mesh CARGILL

40

34

>20 mesh CARGILL

60

54

57

<20 mesh CARGILL

20

78

38

<20 mesh CARGILL

40

54

57

<20 mesh CARGILL

60

27

79

>10 mesh CARGILL

20

85

33

>10 mesh CARGILL

40

50

60

>10 mesh CARGILL

60

46

63

10-20 mesh CARGILL

20

53

58

10-20 mesh CARGILL

40

36

71

10-20 mesh CARGILL

60

30

76

20-40 mesh CARGILL

20

57

55

20-40 mesh CARGILL

40

31

75

20-40 mesh CARGILL

60

33

74

<40 mesh CARGILL

20

45

64

<40 mesh CARGILL

40

62

51

<40 mesh CARGILL

60

22

83

pelletized GPC

20

68

46

pelletizedGPC

40

34

73

pelletized GPC

60

49

61

powdered GPC

20

66

48

powdered GPC

40

42

67

powdered GPC

60

75

40

LSD005

44

93

Table 70. Survival after a period of moisture stress of creeping bentgrass receiving surface applied (PRE) Cargill and Grain
Processing com gluten meal materials.

Treatment
Untreated control

lbs/1000 fit2

Mean Plant
Survival

0

148

% Reduction in Plant
Survival
—

>20 mesh CARGILL

20

29

80

>20 mesh CARGILL

40

36

76

>20 mesh CARGILL

60

27

82

<20 mesh CARGILL

20

52

65

<20 mesh CARGILL

40

34

83

<20 mesh CARGILL

60

24

84

>10 mesh CARGILL

20

77

48

>10 mesh CARGILL

40

54

64

>10 mesh CARGILL

60

31

79

10-20 mesh CARGILL

20

48

68

10-20 mesh CARGILL

40

28

81

10-20 mesh CARGILL

60

26

82

20-40 mesh CARGILL

20

74

50

20-40 mesh CARGILL

40

32

78

20-40 mesh CARGILL

60

24

84

<40 mesh CARGILL

20

76

49

<40 mesh CARGILL

40

55

72

<40 mesh CARGILL

60

21

86

pelletized GPC

20

38

74

pelletized GPC

40

33

78

pelletized GPC

60

33

78

powdered GPC

20

62

58

powdered GPC

40

55

63

powdered GPC

60

32

78

LSD005

33

94

A Greenhouse Study on the Environmental Requirements for Forecasting
Pythium Blight on Golf Courses
J. Livingston, F.W. Nutter, andN.E. Christians
Pythium blight, caused by Pythium aphanidermatum (7), is a warm weather turfgrass disease that can
destroy extensive turf areas very quickly. In the aftermath of a severe outbreak of Pythium blight, it is
usually necessary to re-establish the turfgrass species (2).
Pythium aphanidermatum is a foliar pathogen, and is first seen on turf as irregular water-soaked spots.
Later, leaves fade to a light brown color and senesce. Patches of diseased areas then combine to form
streaks of diseased turf which can be as large as ten feet in diameter. Diseased plants often have a greasy
appearance and may be covered with white, cobweb-like mycelium.
P. aphanidermatum belongs to the Oomycetes family of fungi. Oomycetes are water-loving organisms
which spread rapidly in saturated soils. This is why blighting frequently coincides with surface water
drainage patterns (2). The fungus sexually produces a resistant, overwintering structure called an
oospore. When conditions are favorable, oospores (located mostly in the thatch layer) may germinate
and infect healthy turfgrass. The newly formed mycelia then actively spreads from plant to plant, as well
as by surface drainage and mowing (3).
Little is known about the factors affecting oospore germination in soil, but according to Adams (1971), a
soil temperature of 30°C, and a pH of 7.5 was needed for optimum P. aphanidermatum oospore
germination(l). The disease is also more severe on high alkaline soils combined with high fertility.
Plants grown under low calcium conditions are also more susceptible to Pythium blight(2).
Pythium blight has been widely known by superintendents to be dependent on two important
environmental factors: temperature and moisture. Disease is most likely to occur when the maximum
daily temperature is higher than 30°C, followed by at least 14 hours of high relative humidity (at least
90%). If the minimum temperature during the high relative humidity time period does not drop below
20°C, then conditions are considered favorable for Pythium blight development. Below 20°C, there is
little or no risk of the disease (7).
Golf course superintendents can make use of these environmental requirements to determine when to
apply fungicides to prevent damage from the disease. By limiting fungicide applications to only those
periods of time which are favorable for Pythium development, a superintendent can be both
environmentally safe and more cost efficient(5). Management practices such as fertilization, mowing,
irrigation, and syringing can also be altered to make conditions less favorable for the pathogen, thereby
reducing the need for fungicide applications.
The above forecasting system is based on work done by F.W. Nutter (7). The system was developed by
placing hygrothermographs, instruments that monitor temperature and relative humidity, on golf courses
in areas that represented different levels of disease risk. Hygrothermographs were placed where Pythium
blight frequently occurred, where the disease had occurred in some years, and in areas where disease
seldom occurred. Each hygrothermograph was housed and placed about 15 cm above the soil line.
Pythium outbreaks were visually monitored daily for disease presence in relation to the temperature and
relative humidity data collected from earlier studies. When the hygrothermographs recorded maximum
temperatures at greater than 30°C, along with 90% relative humidity for at least 14 hours, and the
minimum night time temperature above 20°C, Pythium blight was correctly forecast with 96% accuracy
(7). Testing in Iowa during 1991 to 1994 has demonstrated that the forecasting model works very well in
this region.

95

Although much of the research to date has been conducted in the field, controlled environment
experiments are needed to verify the model and to improve on the forecasting system in its present form.
Controlled environment studies on Pythium blight have not been widely reported. Therefore the purpose
of this study was to determine the environmental conditions necessary for Pythium blight development
on creeping bentgrass (
Agrostispalustris) using controlled environmental chambers.
First, it was necessary to use a Pythium inoculum that could be distributed evenly over a potted area. An
air-dried com cob medium infested with Pythium aphanidermatum as developed by Nutter and Cole(8)
was used for the greenhouse study. When properly dried, the inoculum contains only oospores(8).
The medium was prepared by placing 250 grams of number 4 com cob pellets into a 2 Liter flask and
adding 100 mis of distilled water. The pellets were then allowed to expand (5 min.) before 4 grams of
calcium carbonate dissolved in another 100 mis of water was again added to the flask. Two flasks were
prepared in this way; one to be inoculated and one to be used as the control. The flasks were capped and
autoclaved twice for 45 minutes(121 °C at 15 psi). One flask was then aseptically inoculated by placing
5 discs from each of three isolates of Pythium aphanidermatum grown on com meal agar into the flask.
The flasks were then placed in an incubator at 27°C for 14 days. After 14 days, the inoculum was placed
into sterile pans covered with 4 layers of cheesecloth, and then air dried in the pans for 8 days. Once dry,
the inoculum (which contains oospores) was stored in air tight containers until the time of inoculation
( 8 ).

Five maximum temperature treatments were randomly assigned to separate temperature controlled
chambers. The five temperatures were as follows: 21, 24, 27, 30, and 33 °C.
For each temperature treatment, two 4" pots of Penncross creeping bentgrass seedlings (14 day growth),
seeded at a rate of 0.05 g/dm2, were put into each temperature chamber. One pot contained about 2.5
grams of com cob inoculum placed about 2 cm under the seed at the time of seeding, and the other
contained the same amount of the non-inoculated control. The bentgrass was seeded into a sterile
mixture of soil, sand, peat, and perlite (1:1:1:1, v:v). Each temperature treatment was replicated four
times. After each replication, the temperature chambers were again randomly assigned the five
temperatures to be tested.
The seedlings were left in the temperature chambers for 8 hours, and were then placed into a high
humidity dew chamber set at 24°C until Pythium blight was observed. The treatments were checked at
two hour intervals after the first 12 hours of incubation.
Appearance of Pythium blight did not occur on any treatment during the initial experiment. The study
was concluded after 20 hours incubation. Only after the treatments were again placed in very high
temperature stress for over 10 hours, and then placed in a dew chamber for approximately 48 hours, did
any sign of Pythium blight appear. It was not possible in this study to determine if the disease had
actually originated from oospores in the com cob inoculum.
Growth inhibition of the seedlings was observed early in the experiment, which was probably due to the
effects of the com gluten material in the inoculum. Also, many soil saprophytes were observed on the
soil media during seedling germination. What affect the saprophytes had on the Pythium inoculum is
unknown.
In a subsequent experiment, bentgrass plants were inoculated with new CCI amended with V-8 juice to
increase oospore formation. The inoculum was mixed 1:1 with the greenhouse mix and was added to the
upper layer of the treated pots.

96

After about 10 hours of high temperature stress at 33 °C, the 6 week old treatments were then placed in a
dew chamber until Pythium blight was observed. Pythium infection was noticed as early as 36 hours
after the treatments were placed in the dew chamber. When treatments using both the non-amended
inoculum and the V-8 amended inoculum were run side by side, only the V-8 inoculated treatments
became infected with Pythium blight. The number of hours until Pythium blight was observed varied
from 36 to 60 hours for each of three replications.
There are a few possibilities that can be discussed as to why Pythium blight was not observed during the
initial experiment. For instance, the inoculum being placed 2 cm below the soil mixture could have
inhibited oospore germination. It is also possible that the pH of the soil was not at an optimum for
disease development. A new experiment has been started which tests Pythium blight development using
inoculum mixed 1:1 with the soil mixture, and with the inoculum placed on the soil surface.
Another reason for the lack of disease development could be with the inoculum itself. Only a few
oospores were visible in the com cob pellets, not as many as was desired. V-8 juice was later tried, and
the juice seemed to help stimulate oospore formation. There is also research which suggests that
lecithins, phospholipids obtained from egg yolk, stimulate and induce oospore formation in Pythium
aphanidermatum{4). In future experimentation, careful cultures of the dry inoculum will be used to try
to ensure a large population of oospores in the inoculum. The possible use of other types of inoculum,
such as infested rye grain, is also being evaluated.
The data obtained on the environmental requirements of Pythium blight in controlled environments to
date is not conclusive. Obviously, some requirement was not met during the study. Important
knowledge on the methodology necessary to produce Pythium blight on turfgrass in the greenhouse was
obtained for use in further research.
L i t e r a t u r e C it e d :

1.

Adams, Peter B. 1971. Pythium aphanidermatum oospore germination as affected by time,
temperature, and pH. Phytopathology 61:1149-1150.

2.

Couch, H.B. 1973. Pythium Blights. Pages 97-101 in: Diseases of Turfgrasses. R.E. Krieger
Publishing Co., Huntington, NY. 348 pp.

3.

Joyner, B.G. and Larsen, P.O. 1980. Pages 41-47 in: Advances in Turfgrass Pathology.
Harcourt Brace Jovanovich, Inc., Duluth, MN. 197 pp.

4.

Ko, W.H. 1986. Sexual reproduction of Pythium aphanidermatum: stimulation by
phospholipids. Phytopathology 76:1159-1160.

5.

Nutter, F.W. 1980. Forecasting Pythium blight development. Grounds Maintenance. May: pp
28-30.

6.

Nutter, F.W. 1980. Forecasting Pythium. Golf Course Management. June: pp 18-25.

7.

Nutter, F.W., Cole, H., Jr., and Schein, R.D. 1983. Disease forecasting system for warm
weather Pythium blight of turfgrass. Plant Disease 67:1126-1128.

8.

Nutter, F.W. and Cole, H., Jr. 1981. An air-dried com cob medium for greenhouse and field
inoculation of turfgrass involving Pythium aphanidermatum. Plant Disease.

9.

Shane, W.W. 1991. Prospects for early detection of Pythium blight epidemics on turfgrass by
antibody-aided monitoring. Plant Disease 75:921-925.
97

Managing

DrySpots on Bentgrass Putting Greens
D. D. Minner, S. Bughrara and J. H. Dunn

Preliminary results from our topdressing trials with calcined clay indicated that there may be some
inhanced cooling and moisture retention properties associated with calcined clay topdressing. Instead of
just topdressing with calcined clay, our goal was to incorporate some of the material by topdressing
following hollow tine coring. The study was situated on an area of the green that had a history of dry
spot and was difficult to manage.
Year 1-1993
A localized dry spot study was developed in the southwest comer of the small USGA Green located at
the University of Missouri Turf Research Center, Columbia, MO. The green was constructed in the
spring of 1992 and sodded with creeping bentgrass from Rohoza Sod Farm in Pennsylvania. This 25 ft x
25 ft area of the green has approximately a 3% slope and required daily hand syringing. On 30 July the
dry spot.trial was divided into two areas for treatment. The highest location had the most severe dry spot
injury and the lower location had only moderate dry spot injury. Two treatments consisted of
topdressing with sand or Profile. There were six replications of each 2 ft x 12 ft treated plot per location.
A 3/32-inch topdressig was applied for each treatment immediately following hollow core aerification
with 3/8-inch tines on two-inch centers. The three-inch cores were removed before topdressing and the
topdressing was lightly broomed into the holes. On 14 October topdressing treatments were applied at
1/32 inch without core aerification. Plots were watered with overhead irrigation and by hand to promote
recovery of the dry spot areas. Data collected on 1 September represents the level of injury that typically
occurs after our highest summer stress period. Data collected on 14 October represents the amount of
turf recovery that occurred when cooler temperatures promoted better growing conditions.
On 1 September, following the summer stress period, Profile topdressing significantly improved turf
quality and reduced dry spot injury (Table 71). In the severe dry spot location, turf quality was 5.0 for
Profile and 3.3 for the sand. Profile also had 23% less dry spot injury. On 14 October, after the fall
recovery period, Profile topdressed plots had a turf quality of 5.7 compared with just 4.0 for sand. The
net result is that there was 25% more turf cover with Profile-treated plots compared to sand. This trend
for improved turf with Profile was also evident in the "moderate dry spot" location.
Core aerification and topdressing of sand-based greens with Profile significantly improves turf quality
and reduces the amount of turf injury from localized dry spots.
Year 2 - 1994
The same localized dry spot areas of 1993 were again core aerified and topdressed with either Profile or
sand in 1994. Plots were cored on 9 May, 25 June and 17 September of 1994. After each coring,
topdressing materials were applied at 5/16 inch, broomed into holes and watered. From 12 to 18 July,
water was restricted to allow dry spot symptoms to appear. From 19 to 22 July, all plots were hand
syringed once daily to simulate a golf course superintendent's practice of "cooling greens". After 23 July
all plots received sufficient irrigation to promote turf recovery. On 18 September six more replications
of each 2 ft x 12 ft treatment were constructed for drying in 1995. A 3/32-inch topdressing was applied
for each treatment immediately following hollow core aerification with 3/8-inch tines on two-inch
centers. The three-inch cores were removed and topdressing treatments were lightly broomed into the
holes.
The overwhelming observation was that the Profile-topdressed plots never developed severe localized
dry spot. Profile-treated plots also recovered faster and with better turf cover than the sand-topdressed
98

plots (Table 72). Turf plots topdressed with Profile have better quality and color than the sandtopdressed plots (Table 72). The percent of area wilted in the Profile-treated plots was significantly
lower than the area wilted in the sand-treated plots. Dew was less visible on the Profile-treated plots
than the sand-treated plots (Table 72).
Canopy temperatures taken with an infrared thermometer on 20 and 30 July of 1994 were 24.4 and 18°F
cooler on the Profile plots (105 and 105°F, respectively) compared to the sand plots (128.4 and 123.4°F,
respectively). In general, the Profile plots were 6.5 to 9°F cooler during the period from 10 to 29 July.
Soil temperatures at one and three inches below the surface were 1 to 1.4°F cooler in the Profile-treated
plots (Table 72). Profile-treated plots had significantly less topdressing material visible 3 days after
treatment (Table 72).
Turf injury from localized dry spot may be reduced by mid summer coring of problem areas followed by
topdressing with Profile. Irrigation, syringing and green cooling practices will be required to get the
maximum effect from treatment with Profile.

Table 71. Quality and % turf cover of creeping bentgrass on severe and moderate localized dry spot
areas topdressed with sand or Profile.
Severe dry spot location

Topdress
treatment

9/1/93
After stress

Quality

Dry
Spot %
Area

Moderate dry spot location

10/14/93
After recovery

Quality

%
Turf
Cover

9/1/93
After stress

Quality

Dry
Spot %
Area

10/14/93
After recovery

Quality

%
Turf
Cover

Sand

3.3

63.3

4.0

50.8

4.5

32.5

5.3

79.2

Profile

5.0*

40.0*

5.7

75.8*

5.5

17.5*

6.7

94.2*

* Significant at 0.05 probability level.

99

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\ ** Significantly different at the 0.05 and 0.01 probability level.
NS Non-significant.
+ Very hot day.

Table 72. Several parameter measurements for localized dry spot areas. Core aerified and topdressed with Profile and sand on the USGA green
at the MU Turf Research Center in 1994.

cm

Ornamental Studies

Evaluation o f Deciduous Azaleas for Iowa
J. K. lies
The Northern Lights series of deciduous azaleas, resulting from crosses between Mollis hybrids
(.Rhododendron * kosteranum) and rose-shell azaleas {Rhododendronprinophyllum), is the only group of
azaleas that dependably withstand harsh Midwestern winters and annually produce spectacular blooms.
Flower buds on these hybrids have proven to be hardy to -45°F. Northern Lights azaleas can be seen
flowering in late May or early June in a number of vibrant colors. Many other types of deciduous
azaleas are available in the nursery trade today, but we have very little information about their
adaptability to the Iowa climate. Therefore, in the spring of 1994 a deciduous azalea trial was initiated at
the Iowa State University Horticulture Research Station, to evaluate several promising azalea selections
for use in Iowa. Deciduous azaleas were obtained from Roslyn Nursery, Dix Hills, New York, and are
briefly described below.
P la n t M a te ria ls

Rhododendron 'J a n e A b b o t t ' - A hardy, upright plant with fragrant pink flowers that appear in late May.
Rhododendron 'J u l y J e w e l' - Maturing at about 3 feet, this David Leach introduction blooms in early
July with salmon flowers.
Rhododendron 'J u l y J o y ' - Salmon-pink flowers appear in early July on this upright growing David
Leach selection.
Rhododendron 'J u l y J u b ila t io n ' - This well-branched, low-growing David Leach hybrid has fragrant,
bright red flowers with a light orange blotch in mid July.
Rhododendron 'L e m o n D r o p ' - A Weston Nurseries introduction with yellow flowers in early July.
Flowers have a lemony fragrance and autumn foliage is red.
Rhododendron 'P i n k a n d S w e e t' - A Weston Nurseries introduction with fragrant, pink flowers that
appear in July.
Rhododendron 'V in e c o u r t T r o u b a d o u r ' - This dense, upright plant has double red flowers in mid May.
Rhododendron 'V in e la n d D e lig h t ' - This selection bears deep pink flowers on an upright, dense plant.
Rhododendron 'V in e la n d D r e a m ' - An extremely floriferous plant producing bright pink flowers with a
slight orange flare.

101

Crabapples for Iowa Landscapes
J.K. lies

TA X A

FLR1

FR T 2

HTAVD

FO R M 3 C O M M E N T S

'Adams'
'Adirondack'
'Amberina'
'Anne E /
'Autumn Glory'
b a c c a ta 'Walters'
'Bob White'
'Candied Apple'
'Centurion'
'David'
'Donald Wyman'
'Doubloons'

R
W
W
W

DR
R
OR
R
OR
YO
Y
DR
R
R
R
Y
Y
Y
Y
OR
R
R
Y
R
OR
DR
DR
OR
DR
R
R
R
R
R
R
R
O
DR
OR

20/20
20/10
12/12
10/10
15/15
15/15
20/25
15/15
20/15
15/15
20/20
12/10
20/25
20/15
20/15
15/15
20/20
12/15
15/15
20/15
15/15
15/15
20/20
25/25
20/20
18/10
15/15
18/12
25/25
15/15
6/12
15/10
12/12
25/15
15/15
20/20
20/20
25/20
15/20
15/12
12/15

Round
Upright
UpOval
Weeping
Spreading
Round
Horizontal
Weeping
UpSpreading
Round
Round
UpSpreading
Horizontal
UpSpreading
UpSpreading
Round
UpSpreading
Spreading
Weeping
UpSpreading
Horizontal
Rounded
UpSpreading
Round
UpSpreading
Columnar
Weeping
UpOval
UpSpreading
Weeping
Horizontal
Upright
Semi-weeping
UpOval
Weeping
Round
Round
Vase-shaped
Horizontal
UpSpreading
Horizontal

w
w
w
p
R

w
w
w

flo r ib u n d a

P/W

Golden Raindrops™
Harvest Gold®
'Indian Magic'
'Indian Summer'
'Jewelberry'
'Louisa'
Madonna™
Molten Lava®
'Pink Satin'
'Prairifire'
'Professor Sprenger'
'Profusion'
'Red Barron'
'Red Jade'
'Red Jewel'
'Red Splendor'
'Red Swan'

w
w

s a rg e n ta

'Sentinel'
'Serenade'
'Silver Moon'
'Sinai Fire'
'Snowdrift'
Sugar Tyme®
'Winter Gold'
x zu m i 'Calocarpa'
x zu m i 'Winter Gem'
x zu m i 'Wooster'

p
R
W
P
W
W
P
R
W
R
R
W
W
P
W
W
W
W
W
W
W
W
W
W
W
W

0
R

Y
R
R
OR

Dense; one of best reds
Good for parkway use
Yellow fall leaf color
Birds attracted to fruit
Birds attracted to fruit
Yellow fall leaf color
Birds attracted to fruit
Good for espalier
Parkway use if pruned
Post-frost fruit color
Post-frost fruit color
Heavy bloomer
Birds attracted to fruit
Fine-textured
Post-frost fruit color
Excellent fruit display
Red-orange fall leaf color
Birds attracted to fruit
Fine-textured
Double flowers
Birds attracted to fruit
Clear pink flowers
Orange-red fall leaf color
Persistent fruit
Orange fall leaf color
Red-orange fall leaf color
Needs space to develop
Post-frost fruit color
Red-purple fall leaf color
Improved 'Red Jade'
Birds attracted to fruit
Parkway use if pruned
Excellent fruit display
Blooms late in the season
Persistent fruit
Birds attracted to fruit
Persistent fruit
Excellent yellow fruit
Birds attracted to fruit
Small persistent fruit
Good winter fruit color

lFLR=flower color: R=red; P=pink; W=white; P/W=pink and white
2FRT=fruit color: R=red; DR=dark red; 0=orange; Y=yellow; OR=orange-red; YO=yellow-orange
3FORM: UpSpreading = upright-spreading; UpOval = upright-oval

102

Shade and Ornamental Tree Trials
J. K. lies
The Shade and Ornamental Tree Trial project is sponsored by the Iowa Nurserymen's Research
Corporation in cooperation with the Department of Horticulture at Iowa State University. The project
was initiated in 1986, and grows larger each year as new trees are added to the collection. A significant
number of trees in the trial were purchased with funds donated by the Research Corporation, however, in
recent years trees have been donated by several institutions as part of annual "trial packs". In 1995, J.
Frank Schmidt & Son Co. and the Landscape Plant Development Center shipped trees to ISU for
evaluation at the Horticulture Station trial site (USDA hardiness zone 5a). The goal of this project is to
provide reliable plant performance information to industry professionals and to the citizens of Iowa.
Trees that have routinely excelled, or those showing promise are described below.
Acerplatanoides Crystal™ (Norway maple) - A Bailey Nurseries introduction made in Oregon by Max
Lamis. Expected to grow 50 to 60 feet tall, Crystal is noted for a vigorous, straight trunk. It reportedly
has better branching than Emerald Lustre™ with a lighter colored leaf tip.
Acer platanoides Emerald Lustre™ (Norway maple) - Selected in Minnesota and introduced in 1980,
Emerald Lustre™ grows vigorously and develops excellent branching when young. The tree
demonstrates greater winter hardiness than most other Norway maples and its leaves show outstanding
scorch resistance. Trees are expected to grow about 60 feet tall and 50 feet wide.
Acer rubrum Fairview Flame® (red maple) - Although the tree is sold as Acer rubrum, the leaves of
Fairview Flame® are similar to those of many Acer x freemanii cultivars in the trade today. The exact
origin of Fairview Flame® is unknown, however, some think it was a chance selection from a population
of 'Armstrong' seedlings (an Acer * freemanii type). The handsome scarlet to reddish-orange fall leaf
color develops relatively late in central Iowa (late October), yet trees have not suffered winter die-back
or sunscald injury. The tree develops a very uniform canopy, but its growth rate could be characterized
as slow to moderate (6 to 8 inches/year). McGill & Son Nurseries introduced Fairview Flame® and
propagate it on its own roots.
Acer saccharum 'Legacy' (sugar maple) - If you're looking for a sugar maple with a dense, full crown,
leathery dark green leaves that resist scorch and tatter, and excellent long-lasting yellow-orange fall leaf
color, then your choice should be 'Legacy'. 'Legacy' is a Bill Wandell introduction (Discov-Tree
Research) and is expected to grow 50 feet tall and about 35 feet wide. Some growers and retailers in
northern Iowa describe a lack of winter hardiness with 'Legacy', however, this selection is reportedly
thriving in Chanhassen, Minnesota (USDA hardiness zone 4a).
Aesculus x 'Homestead' (buckeye) - 'Homestead' is a buckeye of hybrid origin (
glabra x
Aesculus flava or possibly Aesculus x sylvatica) introduced by researchers from Brookings, South
Dakota. The original tree was planted in the early 1900’s, however, the seed came from a tree near Des
Moines, Iowa. Homestead' has performed admirably throughout the upper Midwest earning it a USDA
hardiness zone rating of 4 (some actually say zone 3). It is a vigorous, strong-growing tree, eventually
developing a broad, rounded form with slightly pendulous lower branches. 'Homestead' begins
producing its characteristic yellowish-white flowers as early as 3 to 4 years of age, but most are sterile
and therefore only a few seeds are produced each year. Summer foliage is dark green and has proven
resistant to leaf-blotch and powdery mildew. Fall color, usually occurring in mid-October, is spectacular
with leaves turning shade of carmine-red and pumpkin-orange.

103

Fraxinus pennsylvanica Prairie Spire™ (green ash) - This male green ash selection from North Dakota
State University is characterized by a striking, narrowly erect growth habit, accented by a strong central
leader and dense lateral branching. Unlike 'Summit' which tends to broaden with age, Prairie Spire™
stays relatively slim, becoming narrowly pyramidal-elliptical as it matures. Summer leaves are dark
green and semi-glossy, but fall color has not lived up to its advance billing. Instead of intense goldenyellow as promised by the introducers, we see uninteresting shades of yellow-brown. Nevertheless,
Prairie Spire™ seems well-suited to street-side or parking lot planter use. The tree is hardy to USDA
hardiness zone 3.
Liquidambar styraciflua Moraine™ (sweetgum) - Sweetgum are not reliably hardy in many parts of
Iowa, however, Moraine™ sweetgum has survived two winters at the ISU Horticulture Research Station
without a hint of branch die-back. Expected to grow 60 feet tall and 40 feet wide, Moraine™ should be
spring-planted in full sun with adequate space for root growth. Dark glossy-green leaves turn brilliant
red and burgundy in fall. Golf course managers should be aware, however, the large woody fruits of
Moraine™ may create a nuisance when they fall from the tree.
Primus maackii (Amur chokecherry) - Hardy at least to -35° F, Amur chokecherry should thrive in just
about any landscape in Iowa. The common name, Amur chokecherry refers to the species's native
habitat along the Amur River in northeastern China. Though Amur chokecherry produces small racemes
of white spring flowers and pea-size dark-purple fruit, the main ornamental feature is its bark. Golden
brown and glossy, it peels off in thin strips when mature. Lit by afternoon sun or seen against a
backdrop of snow, the beautiful bark of Prunus maackii is an unforgettable sight.
Sorbus alnifolia (Korean mountain ash) - Korean mountain ash produces flat-topped clusters of white
flowers in mid-May. Highly ornamental small, pea-sized fruits ripen in September and vary in color
from bright reddish-pink to reddish-purple. As the fruit ripens, leaves change from dark green to a
stunning blend of oranges and browns. Trees will grow 30 to 40 feet tall and about as wide. Sorbus
alnifolia adapts to alkaline soils and prefers good drainage. Its fibrous roots contribute to ease of
transplanting and rapid establishment in the landscape.

104

Evaluating a Gravel Bed System to Improve Survival
and Growth o f Bare-Root Trees Transplanted in
Mid-Summer
J. K. lies and W. R. Graves, Iowa State University
C. Starbuck, University of Missouri

S ig n ific a n c e to N u rs e rv / L a n d s c a p e In d u s tr y

Increasing freight costs, price depression due to competition from mass-market outlets, and labor
shortages are creating pressure on all segments of the nursery/landscape industry to invent and develop
more efficient methods of producing and handling nursery stock. Our proposed research will evaluate
the performance of a gravel bed system that permits the planting of bare-root nursery stock throughout
the growing season. If the performance of gravel bed trees harvested and transplanted in mid-summer is
comparable to the performance of transplanted container-grown and dormant-planted bare-root trees,
then retailers and landscape nurseries will have the option of selling and planting less expensive and
lighter weight bare-root stock all summer. Because this production method does not require the use of
containers, carefully prepared media, and other expenditures ty pical of container culture, substantial cost
savings might be realized which could be passed on to the retail customer.
O b je c tiv e a n d Ju s tific a tio n
T h e o b je c tiv e o f this research is to c o m p a re the g r o w th o f b a r e -ro o t trees held in a g ra v e l bed a n d
fie ld -p la n te d in m id -s u m m e r w ith g r o w th o f d o r m a n t b a r e -ro o t trees fie ld -p la n te d in e a rly s p r in g ,
a n d g r o w th o f c o n ta in e r-g ro w n trees fie ld -p la n te d in m id -s u m m e r. Bare-root nursery stock is less

expensive to produce and ship than container-grown or bailed and burlapped (B&B) stock. Historically,
the use of bare-root stock has been restricted by the perception that it must either be planted in early
spring or potted. But preliminary studies indicate the bare-root planting season might be safely extended
into mid-summer using a novel technique in which bare-root nursery stock is held in a bed of irrigated
gravel (see NM-PRO, March 1995). Results show trees and shrubs held in a gravel bed can be planted in
mid-summer with survival rates equal to, or greater than those expected for container-grown or B&B
plants. As promising as these early results are, additional work is required to better characterize the
performance of gravel bed plants after planting in the field.
P re s e n t S ta tu s o f R e s e a rc h

The initial research on the gravel bed technique was conducted in 1987 at the University of Missouri.
'Hopa' crabapples and 'Whitehouse' callery pears taken from a gravel bed and field-planted in July
showed 100% survival. Subsequent studies using 'Aristocrat' and 'Redspire' callery pear, redbud,
flowering dogwood, maples, lindens, and hybrid tea roses confirmed that trees and shrubs can be planted
bare-root in full leaf in mid-summer with essentially 100% survival if held in a bed of irrigated pea
gravel. In 1994, Sherman Nursery Co. (Charles City, IA) held 500 dormant trees (approximately 30
species) in gravel beds until August 25 before they were field planted. And again, the results were very
encouraging.

105

Research Methodology
Trees of Washington hawthorn (
Crataegusphaenopyrum), Eastern American redbud (
canadensis), green ash (
Fraxinuspennsylvanica), and red maple ( rubrum) were removed from cold
storage at Sherman Nursery Co. (Charles City, IA) in early May 1995, and randomly assigned to three
treatments. Controls (bare-root trees for immediate field planting) and trees to be potted, were packed in
boxes for transport to the Iowa State University Horticulture Research Station (Ames, IA). Containergrown trees were planted in appropriately-sized containers (7-10 gal.) in a bark/sand medium, and grown
until July. Gravel bed trees were placed upright in 18-inch-deep pea gravel at Sherman Nursery,
fertilized with a granular slow-release fertilizer applied to the gravel surface, and drip irrigated with an
automatic system as needed. In late July, gravel bed trees will be harvested from the gravel, sprayed
with water, and transported to the field planting site in Ames where they and the container-grown trees
will be randomly planted among the early spring-planted controls. A slow-release fertilizer will be
applied to gravel bed and container-grown trees after field planting. Trunk caliper and length of the
longest four shoots will be measured at the end of the first, second, and third growing season.

106

Introducing

Introducing
Iowa State University Personnel
Affiliated with the Turfgrass Research Program

D a v e A n d e rs o n

Former Graduate Student and Research Associate
Horticulture Department M.S. (Agnew, M./ Christians)
Presently with Ringer Corporation

B a r b a r a B in g a m a n , P h .D .

Postdoctoral Research Associate, Horticulture Department

D o u g C a m p b e ll

Research Associate, Horticulture Department

N i c k C h r is tia n s , P h .D .

Professor, Turfgrass Science Research and Teaching
Horticulture Department

J i m D ic k s o n

Field Manager, Horticulture Department

P a u la F l y n n

Extension Associate, Plant Disease Clinic
Plant Pathology Department

D a v id G a r d n e r

Graduate Student and Research Associate
Horticulture Department M.S. (Christians)

Ja s o n G a te s

Undergraduate Honors Student
Horticulture Department (Christians)

M a r k G le a s o n , P h .D .

Assistant Professor, Extension Plant Pathologist
Plant Pathology Department

C lin to n H o d g e s , P h .D .

Professor, Turfgrass Science Research and Teaching
Horticulture Department

Jessica L a t t a

Lab Technician, Horticulture Department

D o n a ld L e w is , P h .D .

Associate Professor, Extension Entomologist
Entomology Department

D ia n n a L i u , P h .D .

Postdoctoral Research Associate, Horticulture Department

J o e L iv in g s to n

Undergraduate Research Associate, Horticulture Department

Ja s o n M a n f u ll

Field Technician, Horticulture Department

S c o tt M ille r

Field Technician, Horticulture Department

D a v id M i n n e r , P h .D .

Associate Professor, Extension Turfgrass Specialist
Horticulture Department

R ic h a r d M o o r e

Superintendent Horticulture Research Station

107

Steve Nelson

Field Technician, Horticulture Department

Forrest Nutter, Ph.D.

Associate Professor, Plant Pathologist
Plant Pathology Department

Gary Peterson

Extension Field Specialist - Horticulture

Jason Peterson

Field Technician, Horticulture Department

Steve Starrett, Ph.D.

Former Research Associate
Horticulture Department Ph.D. (Christians)
Presently at Kansas State University, College of Engineering

J. Bryan Unruh

Graduate Student and Research Assistant
Horticulture Department Ph.D. (Christians)

Companies and
Organizations

Companies and Organizations That Made Donations
or Supplied Products to
the Iowa State University Turfgrass Research Program

Special thanks are expressed to the Big Bear Turf Equipment Company and Cushman Turf for providing
a Cushman Turfgrass Truckster; to Tri-State Turf and Irrigation for providing a Greensmaster III Triplex
Greensmower, a Groundsmaster 220 rotary mower, and irrigation equipment; to Great American
Outdoor/Grass Roots for providing a Triplex Greensmower; to Standard Golf Company for providing a
Topdress Broom; and, to Rainbird Irrigation Company for irrigation equipment for use at the research
area.

AgrEvo
8512 Winston Avenue
Des Moines, IA 50522

Gardens Alive
5100 Schenley Place
Lawrenceburg, Indiana 47025

American Hoechst Corporation
Agricultural Chemicals Department
Route 1 - Box 7
Brownsdale, Minnesota 559 i 8

Grain Processing Corporation
PO Box 349
Muscatine, Iowa 52761
Grace Sierra
PO Box 4003
Milpitas, California 95035-2003

Big Bear Turf Equipment Company
10405 T Street
Omaha, Nebraska 68127

Great American Outdoor/Grass Roots Turf
10100 Dennis Drive
Urbandale, Iowa 50322

Ciba Corporation
Agriculture Division
Greensboro, North Carolina 27049

Iowa Golf Course Superintendents
Association

Coron Corporation
PO Box 198
Souderton, Pennsylvania 18964

Iowa Professional Lawn Care
Association

Cushman Turf
5232 Cushman
Lincoln, Nebraska 68501

Iowa Sports Turf Managers
Association

D & K Turf Products
8121 Parkview Drive
Urbandale, Iowa 50322

Iowa Turf Producers and
Contractors
Iowa Turfgrass Institute

DowElanco
Midland, Michigan 48674

LESCO Incorporated
PO Box 10915
Rocky River, Ohio 44116-0915

Earthgro
P.O. Box 143
Lebanon, Connecticut 06249

Lyman-Ritchie Sand & Gravel
4315 Cuming Street
Omaha, Nebraska 68131

Enviro-Gro Technologies
P.O. Box 5036
Lancaster, Pennsylvania 17601-0036

109

Box 218
Quimby, Iowa 51049

Milorganite
735 North Water Street
Milwaukee, Wisconsin 53200

The Toro Company
Irrigation Division
Riverside, California 92500

Monsanto Company
Agricultural Products Division
800 North Lindbergh Boulevard
St. Louis, Missouri 63167

Tri State Turf & Irrigation Co.
6125 Valley Drive
Bettendorf, Iowa 52722

PBI/Gordon Corporation
PO Box 4090
1217 West 12th Street
Kansas City, Missouri 64101-9984

United Horticultural Supply
4564 Ridge Dr. NE
Salem, Oregon 97303

Pickseed West Incorporated
PO Box 888
Tangent, Oregon 97389

Weathermatic Corporation
Telsco Industries
P.O. Box 180205
Dallas, Texas 75218-2005

Pursell
P.O. Box 450
201 W. Fourth St.
Sylacauga, Alabama 35150

Williams Lawn Seed Company
PO Box 112
224 South Hills Drive
Maryville, Missouri 64468

O. M. Scott and Sons
14111 Scottslawn Road
Marysville, Ohio 43041
R.G.B. Laboratories Incorporated
1531 Charlotte Street
Kansas City, Missouri 64108
Rainbird Irrigation Company
Rhone-Poulenc Chemical Company
PO Box 125
Black Horse Lane
Monmouth Junction, New Jersey 08852
SportGrass, Inc.
6849 Old Dominion Drive, Suite 219
McLean, Virginia 22101
Spraying Systems Company
N Avenue at Schmale Road
Wheaton, Illinois 60187
Standard Golf Company
PO Box 68
Cedar Falls, IA 50613
Sustane Corporation
P. O. Box 19
Cannon Falls, Minnesota 55009

Terra Chemical Corporation

110

...and justice for all

The Iowa Cooperative Extension Service's programs and policies are consistent with pertinent
federal and state laws and regulations on nondiscrimination regarding race, color, national origin,
religion, sex, age, and disability.
Cooperative Extension Service, Iowa State University of Science and Technology and the United
States Department of Agriculture cooperating. Robert M. Anderson, Jr., director, Ames, Iowa.
Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914.