'\

WA
vu, ‘

  

__.. ..
"'1' i: -?‘ Fl. P

r; ,. «E;

‘w'wvv— —

 

-, x': - . .
'f‘d'. A:

1" -w-v.,

.- (A m.

, . .3. -
I”, :yvqll'vlr'. v -

 

mem A

{1:} ".7

.‘,n-zr.>
..‘ 5
12' b“

' F

3r ":‘

f3

 

A
V};

{A
‘43

X "“n» I"
IV: "I" ‘
5.3 rue . f'“ ‘
A ' .
MW?" .'

‘ "33+?‘w. .

“ '; ['WMI M .

.. “’5? n". we:
"3':

,A

1r
I . 5”].
‘ » - - I :9; , ‘ rim,
«fr ' ~' )4. ' ' , 3 ‘ j . It»; .
Iv phi-.91 . “"5“ ’13.?“ V , ' . 2 .
‘ : "‘9 gm - , .
i

“3:?

vfl‘vf" ‘

 

" Jun

. 235'.)
mph}? 1. 4
.5; ""4:- ‘

1 {1‘

‘.)‘.‘U

"U

A.»‘ ’
”.5 .v...‘ yr-a—v- _
~~-~ r;*::r:,1:-"'M ....~
53' ~K~.--;..--~
Ma's: 7:. “m
m.-.“ -- -
w -:‘.:r~;:..
0 ._.L m -w.
_ ”WWW,
m“...

a,
..

 

 

.' __

_ _ .27.;“7. wrwr"

"‘1‘“ ;'_"",."'::;1:: n.
-~v"'..J‘ 1“.” ”M;-

a—. f. M A M
N

 

_..
.. ‘
1-3:: ,4,

~ 4. "w:

 

.1': '3 ..- wax-W,
w.- -
' .. ~"-“-‘:~. 4:3. - 337:}-
‘zIz'z an afi :..

. . --.

Jr W

 

 

   

022471/3g5’

TE

mlllllljflllullllllllllli‘ll

00784€KH1

 

LIBRARY
Michigan State
l University

 

 

 

This is to certify that the

dissertation entitled

Postemergence Quackgrass [Elytrigia repens (L.) Nevski]
Control in Corn with Sulfonylurea Herbicides

 

presented by

Joseph A. Bruce

has been accepted towards fulfillment
of the requirements for

Ph.D. degreein Crop and Soil Sciences

 

 

 

Date M7 2:; (6292.,

MS U is an Affirmative Action/Equal Opportunity Instirun'on 0-12771

PLACE IN RETURN BOX to remove this checkout from your record.
TO AVOID FINES return on or before date due.

‘ W

DATE DUE DATE DUE DATE DUE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MSU Is An Affirmative Action/Equal Opportunity Invitation
cmmut

 

POSTEMERGENCE QUACKGRASS El i i (L.) Nevski] CONTROL
IN CORN WITH SULFONYLUREA HERBICIDES

By

Joseph A. Bruce

A DISSERTATION

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Crop and Soil Sciences

1992

ABSTRACT

POSTEMERGEN CE QUACKGRASS mm (L.) Nevski] CONTROL
IN CORN WITH SULFONYLUREA HERBICIDES

By

Joseph A. Bruce

Field experiments were conducted to examine the effects of herbicide rate, growth
stage, cultivation, and adjuvants on quackgrass control with nicosulfuron and primisulfuron.
Greenhouse experiments examined the effect of adjuvants, plant growth stage and
environment on absorption, translocation, and activity of nicosulfuron in quackgrass.

Field applications of nicosulfuron controlled four-leaf quackgrass more effectively
than two-leaf plants. Primisulfuron activity was similar regardless of quackgrass growth .
stage. Sequential applications of either herbicide provided greater full-season control than
single applications to Mo-leaf but not four-leaf plants. Cultivation 10 days after nicosulfuron
and primisulfuron applications often increased early season weed control. Nicosulfuron (35
g ai ha") and primisulfuron (40 g ha") applied postemergence provided quackgrass control
equivalent to glyphosate (840 g ha") applied early preplant in conventional tillage corn
production.

In greenhouse studies, foliar absorption of 14C-nicosulfuron and l‘C-prirnisulfuron
by quackgrass was greatest with petroleum oil adjuvant (POA) plus urea-ammonium nitrate
liquid fertilizer (UAN). The addition of UAN to POA provided greater nicosulfuron and
primisulfuron absorption and activity in quackgrass than with POA alone. Translocation of
foliar applied l‘C-nicosulfuron was more rapid with POA plus UAN than with UAN alone.

Few differences were observed between adjuvants in the field efficacy trials. Nicosulfuron

and primisulfuron activity was occasionally decreased by the addition of atrazine.
Combinations with atrazine did not reduce l“C-nicosulfuron or l“C-primisulfuron uptake by
quackgrass. Foliar absorption of 1‘C-nicosulfuron by quackgrass was greater in one-leaf than
in five-leaf plants. Total 1“C translocation was similar regardless of growth stage. Despite
similar translocation, nicosulfuron more effectively controlled three- and five-leaf quackgrass
than one-leaf plants. Absorption, translocation, and accumulation of foliar applied “C-
nicosulfuron increased as air temperatures increased from 11 to 31 C. However,
nicosulfuron phytotoxicity in well-watered plants was similar. Soil water potentials of -0.03
and -0.2 MPa had little or no impact on l‘C—nicosulfuron absorption, translocation of
accumulation in quackgrass. However, as air temperatures increased, quackgrass control
decreased under soil water potential of -0.2 MPa. Differences in nicosulfuron phytotoxicity
due to growth stage or environmental conditions were not explained by differences in 1‘C

absorption, translocation, or accumulation.

ACKNOWLEDGEMENTS

I would like to thank the members of my graduate committee, Drs. Bernie Zandstra,
Jim Flore, Don Penner, and Jim Kells for their helpful advise and contributions to my
research. A special thank you to Dr. Don Penner for his support and advise regarding my
research project and especially during my job search. I suppose we now know the "Best” way
to handle an unusual job situation. I would to thank my major advisor Dr. Jim Kells for his
generous support, guidance, and friendship during my graduate career at Michigan State.
Now that I am leaving, I hope you find great comfort in the fact that you can safely ride in
307 to the research plots.

A sincere thanks goes out to Frank Roggenbuck and Steve "The Kid" Hart for
extending their advise on laboratory techniques and systems for minimizing the wrath of the
1‘C god. Field research assistance was gratiously provided by Jay ”Meister" Schmidt, Boyd
"The Lure” Carey, Andy "The Pole” Chomas (be thankful I used that nickname), Paul
Knoerr, and Karen Geiger. My sincere gratitude goes to Christy Sprague for her assistance
in this research. Without the camaraderie and antics of those already mentioned including
Troy "The Ghandi" Bauer, Aaron ”Sammy” Hager, and Jason "Woodsie' Woods, I am sure
my sanity would have been gone long ago.

I cannot express enough gratitude to my wife, Kathy, for her understanding,
assistance, support, and love during the past four years. Hopefully, we can now enjoy

bountiful returns.

iv

TABLE OF CONTENTS

Chapter 1: Review of Literature, Quackgrass Biology and Control in Corn

Name .......................................................... 1
Description ..................................................... 1
Distribution and habitat ............................................ 2
Growth and development ........................................... 3
Sexual reproduction ............................................... 5
Asexual reproduction .............................................. 5
Economics of quackgrass ........................................... 6
Quackgrass control in corn ......................................... 8
Literature cited .................................................. 16
Chapter 2: Quackgrass [EMS (L.) Nevski] Control in Conventional and No-
Tillage Corn Production With Glyphosate, N icosulfuron, and Primisulfuron.
Abstract ........................................................ 22
Introduction ..................................................... 23.
Materials and Methods ............................................ 25
Effect of application timing ................................... 25
Effect of cultivation ......................................... 28
Quackgrass control in no-tillage ................................ 29
Data analysis .............................................. 29
Results and Discussion ............................................ 31
Effect of application timing ................................... 31
Effect of cultivation ......................................... 34
Quackgrass control in no-tillage ................................ 36
Acknowledgements ............................................... 38
Literature Cited .................................................. 39

Chapter 3: ADJUVANT EFFECT ON ABSORPTION AND ACTIVITY OF
NICOSULFURON AND PRIMISULFURON IN QUACKGRASS [112mm
Isms (L) Nevsld].

Abstract ........................................................ 41
Introduction ..................................................... 42
Materials and Methods ............................................ 44

Greenhouse research ........................................ 44

V

Herbicide distribution in leaf components .................. 46

Effect of adjuvants on absorption ......................... 46

Herbicide efficacy ..................................... 47

Field research ............................................. 47

Data analysis .............................................. 48
Results and Discussion ............................................ 48
Herbicide absorption ........................................ 48
Herbicide distribution in leaf components .................. 50

Effect of adjuvants on absorption ......................... 51

Herbicide efficacy ..................................... 56
Acknowledgements ............................................... 58
Literature Cited .................................................. 59

Chapter 4: EFFECT OF GROWTH STAGE AND ENVIRONMENT ON FOLIAR
ABSORPTION,TRANSLOCATION,AND ACTIVITY OF NICOSULFURON

IN QUACKGRASS Was (L.) Nevski].

Abstract ........................................................ 61
Introduction ..................................................... 62
Materials and Methods ............................................ 64
General experimental procedures ............................... 64
Eflect of UAN ............................................. 65
Effect of growth stage ....................................... 66
Effect of air temperature and soil moisture ....................... 67.
Data analysis .............................................. 68,
Results and Discussion ............................................ 69
Effect of UAN ............................................. 69
Effect of grth stage ....................................... 76
Effect of air temperature and soil moisture .......... - ............. 80
Acknowledgements ............................................... 86
Literature Cited .................................................. 87

vi

LIST OF TABLES

Chapter 2: Quackgrass W (L.) Nevski] Control in Conventional and No-
Tillage Corn Production With Glyphosate, Nicosulfuron, and Primisulfuron.

Table 1. Plant height and leaf stage (true leaves) for quackgrass and corn
prior to herbicide application in conventional tillage production. . 27
Table 2. Plant height and leaf stage (true leaves) for quackgrass and corn
prior to herbicide application in no-tillage production. ......... 30
Table 3. Postemergence quackgrass control with nicosulfuron and
primisulfuron as affected by herbicide rate and application timing in
conventional tillage corn production. ...................... 32
Table 4. The effect of herbicide rate, application timing, and cultivation in
conventional tillage corn. ............................... 35
Table 5. Quackgrass control as affected by herbicide rate and application
timing in no-tillage corn production. ....................... 37

Chapter 3: ADJUVANT EFFECT ON ABSORPTION AND ACTIVITY OF
NICOSULFURON AND PRIMISULFURON IN QUACKGRASS Maia

ms (L.) Nevski].

Table 1. Recovery of “C-nicosulfuron and l4C-primisulfuron from quackgrass
leaf components and herbicide efficacy in the greenhouse as affected
by adjuvants. ......................................... 52

Table 2. Foliar absorption of “C-nicosulfuron by quackgrass in the
greenhouse and field efficacy of nicosulfuron as affected by spray
solution adjuvants. .................................... 53

Table 3. Foliar absorption of 1‘C-primisulfuron by quackgrass in the
greenhouse and field efficacy of primisulfuron as affected by spray
solution adjuvants. .................................... 55

Chapter 4: EFFECT OF GROWTH STAGE AND ENVIRONMENT ON FOLIAR
ABSORPTION ,TRANSLOCATION,AN D ACTIVITY OF NICOSULFURON

IN QUACKGRASS W (L.) Nevski].

Table 1. 1‘C recovered from quackgrass at 24, 72, and 168 h after application
of 1‘C-nicosulfuron as affected by UAN. .................... 70

vii

Table 2.,

Table 3.

Table 4.
Table 5.

Table 6.
Table 7.

Table 8.

Accumulation of 1‘C translocated from the treated leaf at 24, 72, and
168 h after application. ................................. 75
The effect of quackgrass grth stage on 1‘C recovery, absorption,
and distribution in quackgrass 168 h after l‘C-nicosulfuron
application. .......................................... 77
Accumulation of 1‘C in quackgrass plant parts 168 h after application
of l‘C-nicosulfuron as affected by growth stage. .............. 78
Quackgrass control in the greenhouse with nicosulfuron as affected
by quackgrass growth stage. ............................. 79
The effect of day/night air temperature and soil water potential on
1‘C recovery, absorption, and distribution in quackgrass 168 h after
application of 1‘C-nicosulfuron. ........................... 82
The effect of day/night air temperature and soil water potential on
distribution of 1“C translocated for the treated leaf 168 h after 1‘0

nicosulfuron application. ................................ 83
Quackgrass control with nicosulfuron as affected by day/ night air
temperature, soil moisture, and herbicide rate. ............... 84

viii

LIST OF FIGURES

Chapter 3: ADJUVANT EFFECT ON ABSORPTION AND ACTIVITY OF
NICOSULFURON AND PRIMISULFURON IN QUACKGRASS mm

mm (L.) Nevski].

Figure 1. Foliar absorption of 1‘Ci-nicosulfuron and 1‘C-primisulfuron by
quackgrass as affected by adjuvants. ....................... 49

Chapter 4: EFFECT OF GROWTH STAGE AND ENVIRONMENT ON FOLIAR
ABSORPTION,TRANSLOCATION,AND ACTIVITY OF NICOSULFURON
IN QUACKGRASS IElyjrigia gpgns (L.) Nevski].

Figure 1. F oliar absorption of 1‘C-nicosulfuron in quackgrass as affected by

UAN. .............................................. 71
Figure 2. Accumulation of 1‘C in the treated leaf of quackgrass as affected by

UAN. .............................................. 72.
Figure 3. Translocation of 1‘C from the treated leaf of quackgrass as affected

by UAN. ............................................ 74

CHAPTER 1
REVIEW OF LITERATURE
QUACKGRASS BIOLOGY AND CONTROL IN CORN

Name. Quackgrass has been referred to by several different common and scientific names
throughout the world. In 1753, Carl Linnaeus initially named quackgrass Triticum repent
because of its resemblance to wheat (Triticum) and its creeping growth habit (repens) (44).
From 1812 to 1989, the scientific name Agropyron repens (L) Beauv. was used but
quackgrass is currently referred to as Elytr'igia repens (L.) Nevski in the United States. In
portions of Europe the name Ebrmus repens (L.) Gould has also been used extensively (4,
30, 44, 68, 70). Quackgrass is also referred to by many different common names around the .
world. A sampling of theses names include couch, couchgrass, creeping couch-grass,
quickgrass, quitchgrass, scutchgrass, twitchgrass, and devilsgrass (4, 30, 44). -

Description. This member of the Poaceae family is described as an erect perennial which
is spread by seed or rhizome. Rhizomes are round, 1.5 mm in diameter, scaly, creamy white
to pale yellow in color reaching lengths in excess of one meter. Roots are fibrous arising
from rhizome nodes. Culms are hollow, round, 1.5 to 3 mm diameter, erect or curved at
the base, 30 to 120 cm in length, green (young) to tan (mature) in color with tips that are
often very sharp. Leaves are flat, green, finely pointed, 9 mm wide, 6 to 20 cm in length,
seabrous margin upper surface, smooth glabrous lower surface. Leaf sheath is pubescent
on lower leaves, glabrous on upper leaves, round, split, with overlapping margins. Ligule is

a small 0.5 to 1 mm obtuse membrane which is occasionally ciliate. Auricles are small and

clasping at the base of leaves. Inflorescence is an erect, straight, spike, 5 to 30 cm long with
rough margins, having dense or lax spikes resembling that of wheat (17, 30, 70). The unique
distinguishing characteristics of quackgrass are the slender white scaly rhizomes, clasping
auricles, and seed head resembling that of wheat.

Distribution and habitat. Quackgrass is a native of Europe but is now found throughout
the temperate zones of the world (30). The most serious infestations occur in Europe,
northern United States and southern Canada (30), however, it is also found in Australia,
New Zealand, temperate regions of Asia (70) as well as New Guinea (30). The growth of
quackgrass is suppressed by high temperatures and a short photoperiod. These conditions
reduce the ability of quackgrass to compete in hot or tropical regions (30). Despite its
intolerance of warm climates, it is still found in at least 40 countries infesting 32 different
crops (30, 44).

Quackgrass was introduced to North America prior to 1751 during colonization of
the eastern seaboard (56). Quackgrass seed was transported to the region in contaminated
forage grass seed, animal bedding, animal feed, and animal manure (44, 70). Since its
introduction to North America, quackgrass has become the most troublesome perennial
grass species north of the 35th parallel (30, 74). It is closely associated with agriculture and
is commonly found in orchards, lawns, waste areas, roadsides, and railroad embankments
(17, 30, 70).

This cool season grass can grow on soils ranging from dry sand to wet alluvium
regardless of drainage characteristics. However, it grows particularly well on fine structured
soils (30, 70). Soil pH can range from 4.5 to 8, however, the optimum pH ranges from 6.5
to 8 (70). Quackgrass also has a high salt tolerance. Since quackgrass cannot tolerate
contiguous tree and shrub cover it is commonly found in open areas (70). Quackgrass is

typically found growing in colonies due to its’ perennial nature (30). If left undisturbed, it

3

can quickly spread to acquire more than 90% of the biomass of an abandoned field (70).
Because of its ability to spread quickly and its’ persistent rhizome system, quackgrass is
nearly impossible to eradicate (30, 74).

Growth and development. The morphological development of quackgrass has been
examined. Rhizome sections planted in the fall will typically develop aerial shoots prior to
onset of freezing temperatures. Those sections without shoots remain dormant until spring.
Development of aerial shoots in the spring begins between early and mid-April. Once these
primary shoots reach the three- to four-leaf growth stage (mid-May), lateral shoots begin
to develop from nodes closest to the soil surface. These lateral shoots develop into
secondary aerial shoots or tillers (30, 56, 65). Rhizomes initiate from basal buds located on
the aerial shoot below the soil surface during the same time interval (65). These rhizomes
grow horizontally below the soil surface. By late May, rhizomes can have a length of 25 cm.
During the first two weeks of June, rhizome growth can approach 20 to 25 cm week". The
initial aerial shoots elongate and produce flowering spikes. By late June or early July,
rhizome apices begin to turn toward the soil surface to produce new aerial shoots.
Simultaneously, a rhizome bud at the base of the aerial shoot initiates development and
continues horizontal rhizome growth. This process continues until October when rhizome
apices turn toward the soil surface to overwinter. Not all of the apices survive the winter.
The following spring, the rhizome apices and axillary buds at the base of the overwintering
aerial shoot again initiate aerial shoots for the new season (30, 54, 56).

Carbohydrate levels and transport within quackgrass plants have been examined
throughout the growing season. Schirman and Buchholtz (64) found lowest carbohydrate
and rhizome dry matter levels in April during early plant growth. After this period,
carbohydrate levels increased slightly then remained constant throughout the remainder of

the season. Holm et al. (30) reviewed the results of a similar study conducted in Sweden.

4

In this study, decreases in plant dry weight were also observed. However, lowest dry weights
occurred once aerial shoots had developed two leaves. They determined that plants at this
stage were most susceptible to extremes in environment or disturbance by man (30).

Carbohydrate translocation patterns vary greatly during the growing season.
Differences in translocation may significantly impact the level of quackgrass control obtained
with phloem mobile herbicides. Transport of 1‘C-labelled carbohydrate was examined by
Fiveland et al. (21). They found more carbohydrate transport to the rhizomes of three- to
four-leaf quackgrass than two-leaf quackgrass. Rogan and Smith (60) examined
carbohydrate export from primary shoots to developed axillary tillers and rhizomes. There
was mutual translocation between primary shoots and rhizome tillers but not between
primary shoots and axillary tillers. At this time, primary shoots and axillary tillers were
photosynthetically independent. However, rhizome tillers were still receiving small
quantities of assimilate from the primary shoot (60). If phloem herbicide transport is
similar to that of assimilates, herbicide transport to rhizomes would be greater in larger
quackgrass plants with developed tillers than in smaller plants.

Very little is understood about development of rhizome axillary buds. These buds
can remain dormant for a long interval. However, if severed from the parent plant, the buds
are generally released from inhibition and produce shoots. Similar results are observed
when the rhizome apex is detached from the rhizome (65, 70). Robertson et al. (59)
observed bud elongation when the scale leaf covering the bud was removed. Aqueous
extracts from the scale leaves also effectively inhibited bud development. Bud elongation
was greatest when the rhizome apex was removed regardless of the presence of the scale
leaf (59). Growth hormones are believed to be responsible for the control of bud dormancy
(40, 61, 70). Production of IAA (indole-3-acetic acid) in apical regions and transport to

rhizome buds has been suggested for inhibition of bud deve10pment (70). Continuous

5 .
transport of gibberellin from the parent plant may also be responsible for apical dominance
in quackgrass rhizomes (61). Leakey ct al. (40) suspect a combination effect of cytokinin
and auxin may be responsible for bud dormancy. It is likely that multiple factors are
involved in bud dormancy.

Sexual reproduction. Quackgrass is wind pollinated and generally self-sterile (30, 44, 70)
however, some self-pollination has been reported (30, 54). Plants can produce from 15 to
400 seeds per stem but production of 25 to 40 seeds is typical (44, 70). Seed will remain
viable after passing through the digestive system of horses, cows, and sheep but not hogs
(44). Buried seed remain viable for 5 to 10 years (29, 44). Seeds do not require after-
ripening prior to germination (70) but little germination occurs in the fall. Alternating
temperatures from 30 to 20 C will enhance germination (30). Most seeds germinate in the
top 1 to 5 cm of soil (30).

Plants produced from seed have thinner leaves and are initially weaker than plants
grown from rhizomes. The onset of tiller and rhizome development occurs later with
seedling plants than with plants grown from rhizomes. Regardless of the development time
interval, both plants have similar development patterns. Seedlings require approximately
40 days after germination to establish a rhizome system mature enough to withstand tillage
(30). Quackgrass development from seed accounts for a very small portion of the
quackgrass population (56) but it is essential for continued genetic variability (70).
Asexual reproduction. Vegetative reproduction is more important for maintaining
quackgrass population than reproduction by seed (70). Most rhizomes are located within
the uppermost 10 to 15 cm of soil. Optimum shoot emergence occurs from rhizomes
located 2.5 to 7.5 cm below the soil surface. However, shoots can emerge from greater
depths if the rhizome pieces are large. Regardless of the rhizome planting depth,

development of secondary rhizomes will occur within the top 5 to 10 cm of soil (30). Heavy

6

quackgrass infestations have been estimated to produce rhizome masses in excess of 13,400
kg ha'1 (41) and total rhizome lengths of 80 miles acre" (29). Raleigh et al. (56) planted a
one node rhizome segment to examine rhizome production. By seasons end, a 3.3 m
diameter colony had produced 14 rhizomes totaling 135 m in length with 206 aerial shoots.
Despite this prolific rhizome growth, less than one-third of the axillary rhizome buds in a
three year old sod were found to be viable (33). The below ground quackgrass components
typically comprise 60 to 70% of the total plant biomass.

Economics of quackgrass. Man has used quackgrass for soil conservation, animal feed, as
well as various human uses. Quackgrass has been used as a sod builder along roadsides,
dikes, and in other areas where soil erosion may be a problem (44, 70). Established
quackgrass in abandoned fields provides excellent cover for wildlife (70). As a forage grass,
quackgrass is able to produce two cuttings of hay annually with total crude protein content
comparable to that of timothy (44, 70). Dried quackgrass rhizomes have been ground for
flour and utilized in bread for human consumption (18). In Michigan, quackgrass has been
noted for its ability to effectively reclaim nutrients from municipal sewage effluent (44).
Methanol extracts from quackgrass have been effective against mosquito larvae (Aedes
aegypti L.) at relatively low concentrations (66).

Quackgrass is also utilized for its medicinal values. In Tanzania, the effects of arrow
poison could be counteracted by chewing quackgrass and applying the macerated tissue to
the wound (30). Liquid preparations from roots and rhizomes have been used for its
diuretic properties. This property is believed to be due to the high glycolic acid content of
quackgrass (30). Quackgrass has been used for mucilage production because of its relatively
high content (11%). Rhizome extracts were used as a remedy for kidney and bladder
ailments in the early 20th century (44). Despite these advantages, quackgrass is better

known for its detrimental effects.

7

Quackgass reduces crop growth and yield by competing for light, moisture, nutrients,
and by production of allelopathic substances. Corn, soybean, cat, and canola gain yields
have been reduced by the presence of quackgass (3, 36, 50, 76, 77). Corn grain yield
reductions as geat as 37% (77) and 84% (3) have been reported. Delayed ear silking and
delayed corn maturity was attributed 'to quackgass competition (3). Bandeen and
Buchholtz (3) examined nutrient uptake by quackgass. During a single gowing season,
quackgass incorporated 110, 18, and 68 kg ha'1 of nitrogen, phosphorus, and potassium,
respectively. Between 45 and 68% of these nutrients were removed from the soil before
mid-July. Corn yield reduction from this quackgass population was not overcome by
addition of soil nutrients. Since corn quickly forms a canopy over quackgass, competition
for light does not explain continued corn yield loss. They concluded that soil moisture loss
or toxic inhibition by quackgass were likely causes for the remaining corn yield reductions
(3). Young et al. (77) examined the effect of soil moisture on quackgass interference in
corn. Corn yields were similar regardless of quackgass density when soil moisture and corn
nutrient levels were not limiting. With limited soil moisture, quackgass reduced corn gain
yields but irrigation improved yields of quackgass infested corn to a level similar to
irrigated corn without quackgass (3). Based on water consumption alone, quackgass can
sigiificantly reduce corn yields. Kommedahl et al. (37) examined the effect of quackgass
residues on corn gowth in the field. When corn was gown in residue-free areas, plant
heights and gain yields were geater than corn gown in areas containing quackgass
residues. This suggests that allelopathic substances released from quackgass may also
influence corn yields.

The presence of allelopathic substances in quackgass is well documented. These
substances are not exuded from living quackgass tissue (69). Instead, the substances are

released from decomposing quackgass tissue. Extracts from decomposing tissue inhibited

8

the gowth of alfalfa, wheat, oats, peas, edible beans, corn, cucumber, barley, and flax (23,
35, 39, 71). These toxic substances reduce seedling germination, gowth, and legume
nitrogen fixation (23, 39, 71). The inhibitory effect of quackgass tissue was similar
regardless of gowth stage but rhizome tissues have geater inhibitory effects than foliage
(52). Researchers have now isolated a glycoside (23) and two flavonoids (72) from
quackgass rhizomes and foliage, respectively, which were able to inhibit gowth of crop
plants.

Quackgass can reduce crop value and production in ways other than direct
competition. The ability of quackgass rhizomes to pierce and gow through potato tubers
can significantly reduce tuber value (44). Quackgass also serves as an alternate host for
several insects and crop diseases. Bromegass mosaic virus, wheat stem rust, and the wheat
root rot fungi Ophiobalus and Helminthospon’um are commonly associated with quackgass
(44). Cereal leaf beetle (Oulema melanopa (L.) and many other insects are known to feed
upon quackgass (70). By serving as an alternate host, quackgass can harbor these diseases
and insects in areas surrounding fields. Crops gown in these fields may encounter yield
reductions due to infection or feeding by these crop plants.

Quackgrass control in corn. Effective quackgass control progams are essential to prevent
crop yield reductions due to quackgass interference. Through the integation of sound
cultural practices and herbicides, quackgass populations can be reduced to acceptable levels
(65). Providing optimum conditions for crop gowth will enhance its ability to outcompete
quackgass. The optimum use of soil fertility, crop planting date, crop populations, and crop
row widths in combination with good seedbed preparation will help improve crop
competition with quackgass. It is also important to plant a crop which is most competitive
with quackgass (65). Doll and Kutil (15) conducted a four-year study to observe the effect

of corn and soybean crop rotations on quackgass control. They found geatest quackgass

9

biomass in continuous soybeans, intermediate with corn/soybean crop rotation, and least
biomass in continuous corn. The quackgass biomass in continuous corn was one-half of
that observed in continuous soybeans (15).

The use of soil tillage is also important for obtaining adequate quackgass control.
Prior to the development of herbicides, tillage was the primary means of quackgass control.
Repeated soil cultivations at 7 to 21 day intervals during hot dry weather effectively reduced
quackgass infestations (14, 16, 29, 30, 42). This method will effectively control dormant
rhizome buds. Repeated tillage reduced rhizome lengths (29) and enhanced quackgass
gowth by release of dormant rhizome buds from apical suppression (70). Continued
cultivation prevented foliage gowth which is necessary for production of carbohydrates.
The combination of little carbohydrate production and continued use of carbohydrates
during shoot regowth after tillage leads to depletion of carbohydrate reserves and death of
the rhizome (16, 29). Tillage will also move rhizomes to the soil surface where they are
most susceptible to desiccation ( 14, 16, 29, 30, 74). Soil cultivation in the fall also exposes
rhizomes to freezing temperatures which will also lead to death by desiccation ( 14, 16, 30,
70, 74). To utilize tillage for quackgass control, a producer would have to either summer
fallow the land or initiate tillage after summer harvest of a cereal gain crop. For many
producers, this approach does not fit into their crop rotation plans or does not represent a
profitable option.

Quackgass control is often geater when herbicides are used in combination with
tillage (70, 65, 74). The use of either atrazine (6-chloro-N-ethyl-N '-(1-methylethyl)-1,3,5-
triazine-2,4-diamine) or glyphosate (N-(phosphonomethyl)glycine) in conventional tillage
corn production provided geater quackgass control than the same herbicide treatments
utilized in no-tillage corn production (26). Cultivation of quackgass infested soybeans 7

days after postemergence applications of haloxyfop [2-[4-[[3-chloro-5-(trifluoromethyl)-2-

10

pyridinyl]oxy]phenoxy]propanoic acid] (32) and sethoxydim [2-[l-(ethoxyimino)butyl]-5-[2-
(ethylthio)pr0pyl]-3‘-hydroxy-2-cyclohexen-1-one] (67) sigiificantly improved quackgass
control. Cultivation is often substituted for a second application of herbicide in quackgass
control progams utilizing sequential applications of herbicide (14). Soil tillage is an
important tool in the efforts to control quackgass with or without the use of herbicides.

Quackgass suppression or control can be obtained with applications of glyphosate,
EPT C [S-ethyl dipropyl carbamothioate], atrazine, nicosulfuron [2-[[[[(4,6-dimethoxy-2-
pyrimidinyl)amino]carbonyl]amino]sulfonyl]-N,N-dimethyl-3-pyridinemrboxamide], and
primisulfuron [2-[[[[[4,6-bis(difluoromethoxy)-2-pyrimidinyl]amino]carbonyl]amino]
sulfonyl]benzoic acid]. Due to the nonselective nature of glyphosate, it must be applied
prior to crop emergence. Late fall or pre-plow spring applications to actively gowing
quackgass foliage at least 20~cm in height will provide effective control without soil activity
(14, 31, 74). Fall glyphosate applications often provide geater quackgass control than the
same herbicide rate applied in the spring (31). However, many producers find it difficult
to make timely fall applications due to inclement weather or delayed harvests. Spring
applications may delay corn planting beyond optimum dates while waiting for quackgass to
reach the desired application stage (74). Following glyphosate applications, producers must
delay soil tillage at least three days (14, 74). This interval is necessary to allow adequate
herbicide translocation for effective control of rhizome bud tissue (74). Glyphosate
generally provides a level of quackgass control which is persistent for several years (14, 17).

Preplant incorporated applications of EPTC at 6.6 kg ai ha'l will provide some
degee of quackgass suppression. Efficacy is dependent upon thorough herbicide
incorporation (two passes) to depths of 5 to 8 cm (14, 17, 74). Greatest suppression is
obtained when tillage operations cut quackgass rhizomes into small segnents (14, 17, 74).

Control of quackgass with EPTC is increased if atrazine (2.2 kg ha") plus crop oil

11
concentrate is applied either pre-plow or postemergence (14, 17). However, due to the
relative cost of EPTC treatments and the level of quackgass control, EPTC is not widely
utilized for quackgass control in corn.

Selective postemergence quackgass control in corn can be achieved from
applications of atrazine. Optimum control is provided from a pre-plow application of 2.2
kg ha'1 when followed with an additional preemergence or postemergence application of 2.2
kg ha'1 (11, 14, 17). In some instances, the second application of atrazine in this sequential
treatment may be substituted with cultivation without reducing control (14). The pre-plow
application of atrazine is important for obtaining optimum quackgass control. When
applied pre-plow, more herbicide comes in contact with quackgass rhizomes allowing
geater herbicide uptake and control (11, 14). Quackgass control is less consistent with
single applications of atrazine (74). Application rates less than 2.2 kg ha'1 do not provide
adequate control (11). Despite the benefit of postemergence selectivity in corn, atrazine
treatments have some shortcomings. Soil persistence from this treatment will restrict crop
rotation to atrazine tolerant crops the following year (11, 14, 17). These restrictions
combined with recent changes in the registration status in the United States have reduced
the utility of atrazine for quackgass control in corn.

N icosulfuron and primisulfuron are newly available sulfonylurea herbicides which
control many gass and broadleaf weed species when applied postemergence in corn. These
herbicides provide new alternatives for control of troublesome weed species such as
johnsongass [Sorghum halepense (L.) Pers.], shattercane [Sorghum bicolor (L.) Moench], and
quackgass. Both herbicides have high specific activity, requiring only 20 to 70 g ai ha'1 to
provide effective weed control. These herbicides must be applied with an adjuvant to obtain
maximum efficacy. In soils with a pH of 6.8 or less, these herbicides have a relatively short

soil half-er so crop rotation is generally not a problem (1, 2).

12
These sulfonylurea herbicides inhibit acetolactate synthase (ALS) to effectively block

synthesis of the branched-chain amino acids valine, leucine, and isoleucine (1, 49). Previous
research concluded that herbicide phytotoxicity was a result of amino acid starvation (6).
Researchers now believe that accumulation of the toxic metabolite, a-amino butyric acid is
responsible for the phytotoxicity induced by an ALS inhibitor (38, 58). The basis of
herbicide selectivity is by rapid metabolism of the herbicide in tolerant plant species (22, 49,
51). In primisulfuron tolerant barnyardgass [Echinochloa cms-galli (L.) Beauv.],
primisulfuron is rapidly inactivated (within 2 hours) by cytochrome P450-catalyzed
hydoxylation of the pyrimidine ring followed by glycosylation (49, 22). The author is not
aware of documentation regarding the metabolic pathway of nicosulfuron in tolerant species.

Nicosulfuron and primisulfuron have exhibited good activity on quackgass.
Quackgass control in excess of 80% has been reported with both herbicides in conventional
tillage corn production (9, 10, 47, 57). However, less than acceptable control has also been
observed (10, 75). Quackgass control with nicosulfuron was influenced by application rate.
Bhowmik et al. (9) observed quackgass control increase as nicosulfuron application rate
increased from 17.5 g to 35 g ha“. Nicosulfuron rates geater than 35 g ha'1 provided
quackgass control similar to the 35 g ha'1 rate (9). Similar results were observed by Yenish
and Doll (75). Quackgass control was not influenced as primisulfuron rates increased from
20 to 40 g ha ‘1 (7, 47, 75).

The effect of nicosulfuron and primisulfuron application timing on quackgass
efficacy has been examined. Quackgass control was geater when the application of either
herbicide was delayed (75). Bhowmik et al. (9) observed geater nicosulfuron control of
four- to six-leaf quackgass than application on one- to three-leaf or seven- to 10-leaf plants.
However, Reinhart et al. (57) observed similar nicosulfuron control of three- to four-leaf

and five- to six-leaf quackgass. Quackgass regowth following an early postemergence

13

application of primisulfuron (20 g ha") was effectively controlled with a post-directed
application of primisulfuron (24). Optimum quackgass control from postemergence
nicosulfuron and primisulfuron applications may be influenced by quackgass stage of
gowth.

Little research has been conducted to examined the effect of tillage on nicosulfuron
and primisulfuron activity. Hand cultivation of quackgass 4-weeks after nicosulfuron
application did not influence quackgass control (8). However, cultivation after
postemergence application of nicosulfuron increased johnsongass control (73). In no-tiliage
corn production, primisulfuron did not provide acceptable quackgass control (26). In the
same study, nicosulfuron provided unacceptable early season quackgass control, however,
late season control was at least 85% (26). Multiple applications of nicosulfuron and
primisulfuron were necessary to provide acceptable johnsongass control in no-tillage corn
production (63).

Primisulfuron efficacy is influenced by quackgass biotype. Gillespie et al. (25)
observed similar initial control of 15 different biotypes following a postemergence
application of primisulfuron at 20 g ha". However, late season regowth was observed with
some of the biotypes. All biotypes tested had similar 1‘C-prirnisulfuron absorption and
translocation patterns. However, sigiificant differences in spray retention were observed
between the biotypes. They attributed the primisulfuron biotype response to differences in
spray retention and total amount of primisulfuron absorbed (25).

Foliar absorption of nicosulfuron and primisulfuron by target weed species is often
quite low. J ohnsongass absorption of nicosulfuron and primisulfuron plus NIS was only
12% and 3%, respectively (12). In field and geenhouse research, nicosulfuron activity on
geen foxtail [Setaria viridrlr (L.) Beauv.] was dependant upon adjuvant (48). In this research,

methylated seed oil provided geater nicosulfuron activity than petroleum oil adjuvant or

l4

nonionic surfactant (48). Various adjuvants have enhanced the activity of other sulfonylurea
herbicides. Velvetleaf (Abutilon theophmsti Medicus) foliar absorption of thifensulfuron [3-
[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]amino]sulfonyl]-2-
thiophenecarboxylic acid] plus NIS was 15%, 24 hours after application (5). The addition
of 28% urea-ammonium nitrate liquid fertilizer (UAN) to this treatment not only increased
absorption to 38% but also improved velvetleaf control. Fielding and Stoller (19) observed
21% chlorimuron [2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]
benzoic acid] uptake in velvetleaf with NIS and 32% with NIS plus UAN 84 hours after
treatment. In field studies, chlorimuron plus NIS and UAN provided geater velvetleaf
control than chlorimuron plus NIS. However, the effectiveness of an adjuvant can be very
specific. Several researchers have found that adjuvant efficacy is dependant upon the
herbicide being applied and the characteristics of the target weed species (20, 43, 62). The
identification of efficacious adjuvants for nicosulfuron and primisulfuron may further
improve quackgass efficacy.

The weed spectrum controlled by nicosulfuron and primisulfuron can be broadened
through the use of tank-mix combinations with other herbicides. These combinations are
of particular interest to achieve single application, total postemergence weed control. Our
preliminary quackgass control research examined the combinations of atrazine with
nicosulfuron and primisulfuron (10). The addition of atrazine to nicosulfuron and
primisulfuron treatments provided similar or geater quackgass control than identical
treatments without atrazine (10). Other researchers have observed reduced weed control
from these tank-mix combinations. N icosulfuron control of velvetleaf (13) and giant foxtail
(Setan'a faberi Herrm) (45, 46, 55) decreased when applied as a tank-mix combination with
atrazine. Similar results were observed on giant foxtail (13, 27, 34), shattercane (28), and

velvetleaf (27) with primisulfuron. Nicosulfuron and primisulfuron combinations with

15

atrazine would be useful for total postemergence weed control in corn. However, research
is needed to identify possible tank-mix interactions which may potentially reduce quackgass
control.

Environmental factors affecting nicosulfuron and primisulfuron activity have been
examined. Nalewaja et al. (48) observed less effective geen foxtail control when 2 mm of
simulated rainfall fell within 24 h after nicosulfuron application. Greatest control reductions
occurred when simulated rain fell within 1.5 hours after application (48). Air temperature
at the time of nicosulfuron application also influences weed control. Nalewaja et al. (48)
observed geater redroot pigweed (Amaranthus retroflexus L.) control as temperature
increased from 10 to 30 C. Control of geen foxtail was geatest at 20 C, intermediate at
30 C, least at 10 C. With both species, nicosulfuron efficacy was geater at 96 to 100%
relative humidity than at 40 to 50% (48). Oyarzabal and Owen (53) examined soil moisture
effects on shattercane and woolly cupgass [Eriochloa villosa (Thunb.) Kunth] control with
nicosulfuron and primisulfuron. Herbicide activity was geatest on well watered plants.
Absorption of l4C-labelled herbicide in shattercane was similar regardless of soil water
potential. In stressed woolly cupgass, less 1‘C-herbicide was absorbed and translocated than
well watered plants. At present, the effects of air temperature and soil moisture on
absorption, translocation, and activity of nicosulfuron and primisulfuron in quackgass have

not been examined.

10.

11.

12.

13.

Literature Cited

Anonymous. 1990. AccentTM Herbicide. Technical Bulletin. E. I. du Pont de
Nemours and Co. Inc., Agicultural Products Dep., Wilmington, DE. 12 p.

Anonymous. 1988. BeaconTM Herbicide. Technical Release. Agicultural Division,
CIBA- Geigy Corporation, Greensboro, NC. 8 p.

Bandeen, J. D. and K. P. Buchholtz. 1967. Competitive effects of quackgass upon
corn as modified by fertilization. Weeds 15:220-224.

Bayer AG, Agochemicals Division. 1983. Important Weeds of the World. Bayer
AG, Leverkusen, Federal Republic of Germany.

Beckett, T. H. and E. W. Stoller. 1991. Effects of methylammonium and urea
ammonium nitrate uptake of thifensulfuron in velvetleaf (Abutilon theophrasti).
Weed Sci. 39:333-338.

Beyer, E. M., M. J. Duffy, J. V. Hay, and D. D. Schlueter. 1987. Sulfonylurea
herbicides. p. 117-189 in P. C. Kearney and D. D. Kaufman, eds., Herbicides:
Chemistry, Degadation, and Mode of Action. Vol 3. Dekker, NY.

Bhowmik, P. C. and B. M. Bahnson. 1989. Postemergence activity on DPX-V9360
and CGA-136872 in controlling quackgass [Agropyron repent (L.) Beauv.] in corn.
Abstr. Weed Sci. Soc. Am. 29:2-3.

Bhowmik, P. C. and B. M. Bahnson. 1990. Quackgass control in field corn with
CGA-136872 and DPX-V9360. Proc. Northeast Weed Sci. Soc. 44:86.

Bhowmik, P. C., B. M. O’Toole, and J. Andaloro. 1992. Effects of nicosulfuron on
quackgass (Eb/trigia repens) control in corn (Zea mays). Weed Technol. 6:52-56.

Bruce, J. A. and J. J. Kells. 1988. Quackgass (Agropyron repent (L.) Beauv.) control
in corn with selective postemergence herbicides. Proc. North Cent. Weed Control
Conf. 43:33.

Buchholtz, K. P. 1963. Use of atrazine and other triazine herbicides in control of
quackgass in corn fields. Weeds 11:202-205.

Camacho, R. F. and L. J. Moshier. 1991. Absorption, translocation, and activity of
CGA-136872, DPX-V9360, and glyphosate in rhizome johnsongass (Sorghum
halepense). Weed Sci. 39:354-357.

Carey, J. B., P. B. Knoerr, and J. J. Kells. 1992. Herbicide interactions with
nicosulfuron and primisulfuron in corn. Abstr. Weed Sci. Soc. Am. 32:12.

16

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

26.

27.

28.

17’

Doll, J. D. 1981. Quackgass control in field crops. University of Wisconsin
Cooperative Extension Bull. no. A2045.

Doll, J. D. and J. L. Kutil. 1990. Quackgass [Agropyron repens (L.) Beauv.]
reinfestation following glyphosate application for several cropping systems. Abstr.
Weed Sci. Soc. Am. 30:45.

Dunham, R. S. K P. Buchholtz, L. A. Derscheid, A. H. Grisby, E. A. Helgerson, and
D. W. Staniforth. 1956. Quackgass control. Minn. Ag. Exp. Sta. Bull. 434. '

Fawcett, R. S. and V. M. Jennings. 1978. Quackgass and its control. Iowa State
University Cooperative Extension Bull. no. Pm-742.

Femald, M. L. and A. C. Kinsey. 1958. Edible wild plants of eastern North
America. Rev. by R. C. Rollins. Harper, New York, NY.

Fielding, R. J. and E. W. Stoller. 1990. Effects of additives on efficacy, uptake, and
translocation of chlorimuron ethyl ester. Weed Technol. 4:264-271.

Fielding, R. J. and E. W. Stoller. 1990. Effects of additives on the efficacy, uptake
and translocation of the methyl ester of thifensulfuron. Weed Sci. 38:172-178.

Fiveland, T. J ., L. C. Erickson, and C. I. Seely. 1972. Translocation of 1"C-
assimilates and 3-amino-1, 2-, 4-triazole and its metabolites in Agropymn repens.
Weed Res. 12:155-163.

Fonné-Pfister, R., J. Gaudin, K. Kreuz, K. Ramsteiner, and E. Ebert. 1990.
Hydroxylation of primisulfuron by an inducible cytochrome P450-dependant
monooxygenase system from maize. Pestic. Biochem. Physiol. 37:165-173.

Gabor, W. E. and C. Veatch. 1981. Isolation of a phytotoxin from quackgass
(Agropyron repens) rhizomes. Weed Sci. 29:155-159.

Gillespie, G. R., P. J. Porpiglia, and J. W. Peek. 1990. Influence of application
variables on the herbicidal activity of CGA- 136872. Abstr. Weed Sci. Soc. Am. 30:6.

Gillespie, G. R. and D. B. Vitolo. 1992. Response of quackgass [Ebrtrigia repens
(L.) Nevski] biotypes to primisulfuron. Abstr. Weed Sci. Soc. Am. 32:13.

Hahn, R. R. 1990. Quackgass control progams for field corn. Proc. Northeast
Weed Sci. Soc. 44:87.

Hart, 8. E. and D. Penner. In review. Physiological basis for the antagonistic effect
of atrazine on the efficacy of primisulfuron to giant foktail (Setaria faben') and
velvetleaf (Abutilon theophmsti). Weed Sci. in review.

Hart, S. E., D. Penner, and J. J. Kells. 1990. Absorption and efficacy of
primisulfuron from tank-mix combinations with other postemergence herbicides.
Proc North Cent. Weed Sci. Soc. 45:14.

29.

30.

31.

32.

33.

34.

35.

36.

37.

38.

39.

40.

41.

42.

43.

18

Hay, J. R. 1962. Biology of quackgass and some thoughts on its control. Down to
Earth 18:14-16.

Holm, L. G., D. L. Plucknett, J. V. Pancho, and J. P. Herberger. 1977. The World’s
Worst Weeds: Distribution and Biology. University Press of Hawaii, Honolulu. 609

pp.

Ivany, J. A. 1981. Quackgass (Agropyron repens) control with fall-applied
glyphosate and other herbicides. Weed Sci. 29:382-386.

Ivany, J. A. 1991. Effect of haloxyfop on quackgass (Ebrtrigia repens) and potatoes
(Solanum tuberosum). Weed Technol. 5:72-75.

Johnson, B. G. and K. P. Buchholtz. 1962. The natural dormancy of vegetative buds
on the rhizomes of quackgass. Weeds 10:53-57.

Kells, J. J. and P. B. Knoerr. 1990. Tank-mix herbicide combinations for corn with
nicosulfuron and primisulfuron. Proc North Cent. Weed Sci. Soc. 45:17.

Kommedahl, T., J. B. Kotheirner, and J. V. Bernardini. 1959. The effects of
quackgass on germination and seedling development of certain crop plants. Weeds
7:1-12.

Kommedahl, T., K. M. Old, J. H. Ohman, and E. W. Ryan. 1970. Quackgass and
nitrogen effects on succeeding crops in the field. Weed Sci. 18:29-32.

Kommedahl, T., K. M. Old, J. H. Ohman, and E. W. Ryan. 1975. Quackgass and
nitrogen effects on succeeding crops in the field. Weed Sci. 23:29-32.

LaRossa, R. A., T. K. Van Dyk, and D. R. Smulski. 1987. Toxic accumulation of
a-ketobutyrate caused by inhibition of the branched-chain amino acid biosynthetic
enzyme acetolactate synthase in Salmonella ophimun'um. J. Bacteriol. 169:1372-
1378.

Le Toumeau, D. and H. G. Heggeness. 1957. Germination and gowth inhibitors
in leafy spurge foliage and quackgass rhizomes. Weeds 5:12-19.

Leakey, R. R., R. H. Chancellor, and D. Vince-Prue. 1975. Parental factors in
dominance of lateral buds on rhizomes of Agropyron repens (L.) Beauv. Planta
123:267-274.

Linscott, D. L. 1970. The ten worst weeds of field crops. Quackgass. Crop and
Soils 23:8-9.

Lowe, H. J. and K P. Buchholtz. 1952. Control of quackgass. Weeds 1:346-351.

Manthey, F. A. and R. Matysiak. 1990. Oils and emulsifiers affect imazethapyr
phytotoxicity. Proc. North Cent. Weed Sci. Soc. 45:14- 15.

45.

46.

47.

48.

49.

50.

51.

52.

53.

55.

56.

57.

58.

19
Mitich, L. W. 1987. The Devil’s gass: quackgass. Weed Technol. 1:184-185.

Morton, C. A. and R. G. Harvey. 1989. DPX-V9360 for weed control in field and
sweet corn. Abstr. Weed Sci. Soc. Am. 29:2.

Morton, C. A. and R. G. Harvey. 1990. DPX-V9360 for control of giant foxtail
(Setaria faben' Herrm.) in field corn. Abstr. Weed Sci. Soc. Am. 30:4.

Moses, A. J., C. L. Kern, T. B. 'Threewitt, D. E. Stamm, T. D. Taylor, M. D.
Johnson, J. Cantwell, T. R. Dill, and G. R. Gillespie. 1989. Summary of the 1989
CGA-136872 EUP progam. Proc. North Cent. Weed Sci. Soc. 44:36.

Nalewaja, J. D., Z. Woznica, and F. A. Manthey. 1991. DPX-V9360 efficacy with
adjuvants and environment. Weed Technol. 5:92-96.

Neighbors, S. and L. S. Privalle. 1990. Metabolism of primisulfuron by
barnyardgass. Pestic. Biochem. Physiol. 37:145-153.

O’Donovan, J. T. 1991. Quackgass (Elytrigia repens (L.) Nevski) interference in
canola (Bmssica campestris). Weed Sci. 39:397-401.

Obrigawitch, T. A., W. H. Kenyon, and H. Kuratle. 1990. Effect of application
timing on rhizome johnsongass (Sorghum halepense) control with DPX-V9360.
Weed Sci. 38:45-49.

Ohman, J. H. and T. Kommedahl. 1960. Relative toxicity of extracts from
vegetative organs of quackgass to alfalfa. Weeds 8:666-670.

Oyarzabal, E. S. and M. D. K. Owen. 1992. Nicosulfuron and primisulfuron-methyl
activity in shattercane (Sorghum bicolor) and woolly cupgass (Ericchloa villosa)
gown under water stress. Abstr. Weed Sci. Soc. Am. 32:5.

Palmer, J. H. and G. R. Sagar. 1963. Agropyron repens (L.) Beauv. Biological flora
of the British Isles. J. Ecol. 51:783-794.

Radliff, E. E. and G. Kapusta. 1990. Grass control in corn as influenced by
antagonistic interactions between DPX-V9360 and selected postemergence
herbicides. Proc. North Cent. Weed Sci. Soc. 45:28.

Raleigh, S. M., T. R. Flanagan, and C. Veatch. 1962. Life history studies as related
to weed control in the northeast. Quackgass. Univ. Rhode Island Ag. Exp. Sta.
Bull. 365.

Reinhart, M. W., M. J. Dobrotka, and S. W. Rowe. 1989. DPX-V9360 performance
on difficult to control gass species in corn. Proc. North Cent. Weed Sci. Soc. 44:30.

Rhodes, D., A. L. Hogan, L. Deal, G. C Jamieson, and P. Haworth. 1987. Amino
acid metabolism of Lemna minor L. II, Responses to chlorsulfuron. Plant Physiol.
84:775-780.

59.

60.

61.

62.

63.

65.

66.

67.

68.

69.

70.

71.

72.

20

Robertson, J. M., J. S. Taylor, K N. Harker, R. N. Pocock, and E. C. Yeung. 1989.
Apical dominance in rhizomes of quackgass (Elm-igia repens): Inhibitory effect of
scale leaves. Weed Sci. 37:680-687.

Rogan, P. B. and D. L. Smith. 1974. Patterns of translocation of 1‘C-labelled
assimilates during vegetative gowth of Agmpyron repens (L.) Beauv. Z.
Pflanzenphysiol. 73:405-414.

‘ Rogan P. B. and D. L. Smith. 1976. Experimental control of bud inhibition in

rhizomes of Agropyran repens (L.) Beauv. Z. Pflanzenphysiol. 78:113-121.

Roggenbuck, F. C., L. Rowe, D. Penner, L. Petroff, and R. Burow. 1990. Increasing
postemergence herbicide efficacy and rainfastness with silicone adjuvants. Weed
Technol. 4:576-580.

Ross, M. A. 1989. Selective control of johnsongass [Sorghum halepense (L.) Pers.]
in corn. Proc. North Cent. Weed Sci. Soc. 44:40-41.

Schirman, R. and K P. Buchholtz. 1966. Influence of atrazine on control of
rhizome carbohydrate reserves of quackgass. Weeds 14:233-236.

Stobbe, E. H. 1976. Biology of quackgass. Proc. North Central Weed Control
Conf. 31:151-152.

Supavar, P., F. W. Knapp, and R. Nafus. 1974. Biologically active plant extracts for
control of mosquito larvae. Mosquito News 3:398-402.

Waldecker, M. A. and D. L. Wyse. 1984. Quackgass (Agropymn repens) control in
soybeans (Glycine max) with BAS 9052 OH, KK-80, and Ro-13-8895. Weed Sci.
32:67-75.

Weed Science Society of America. 1989. Composite List of Weeds. Weed Science
Society of America. Champaigi, IL. 112 pp.

Welbank, P. J. 1960. Toxin production from Agropyron repenr. Pages 158-168 in J.
L. Harper, ed. The Biology of Weeds. Blackwell Sci. Publ. Oxford, England.

Werner, P. A. and R. Rioux. 1977. The biology of Canadian weeds. 24. Agmpymn
repens (L.) Beauv. Can. J. Plant Sci. 57:905-919.

Weston, L. A. and A. R. Putnam. 1985. Inhibition of gowth, nodulation and
nitrogen fixation of legumes by quackgass. Crop Sci. 25:561-565.

Weston, L. A., B. A. Burke, and A. R. Putnam. 1987. Isolation, characterization,
and activity of phytotoxic compounds from quackgass [Agropymn repent (L.)
Beauv.]. J. Chem. Ecol. 13:403-421.

73.

74.

75.

76.

77.

21

Worthington J. P. 1990. The effect of cultivation, preceding herbicide application
of DPX-V9360, DPX-79406 and CGA- 136872 on control of johnsongass [Sorghum
halepenre (L.) Pers.] in corn. Proc. North Cent. Weed Sci. Soc. 45:34-35.

Wyse, D. L. 1976. Quackgass control in field crops. Proc. North Central Weed
Control Conf. 31:152-154.

Yenish, J. P. and J. D. Doll. 1990. Efficacy of CGA-l36872, DPX-V9360, and DPX-
79406 on quackgass (Agropyron repens (L.) Beauv.) control in corn. Abstr. Weed
Sci. Soc. Am. 30:5.

Young, F. L., D. L. Wyse, and R. J. Jones. 1982. Influence of quackgass
(Agropyron repens) density and duration of interference on soybeans. Weed Sci.
30:614-619.

Young, F. L., D. L. Wyse, and R. J. Jones. 1984. Quackgass (Agropyron repens)
interference on corn (Zea mays). Weed Sci. 32:226-234.

CHAPTER 2

QUACKGRASS El i i m (L.) Nevski] CONTROL IN CONVENTIONAL AND
NO-TILLAGE CORN PRODUCTION WITH GLYPHOSATE,

NICOSULFURON, AND PRIMISULFURON

ABSTRACT

Field experiments were conducted in 1990 and 1991 to examine the effect of
herbicide rate, application timing, quackgass gowth stage, and cultivation on quackgass
control with nicosulfuron and primisulfuron in corn. In conventional tillage, quackgass
control with nicosulfuron was geater when application was made to four-leaf quackgass
than two-leaf quackgass. Primisulfuron provided similar control regardless of quackgass
gowth stage. Sequential applications of nicosulfuron and primisulfuron provided geater
season-long control than single applications of the same rate on two-leaf but not four-leaf
quackgass. Cultivation 10 days after nicosulfuron or primisulfuron application often
increased early season control, but by October few differences were observed.
Postemergence applications of nicosulfuron (35 g ha") and primisulfuron (40 g ha")
provided control equivalent to or geater than an early preplant application of glyphosate
(840 g ha"). Corn yields were similar regardless of the quackgass control progam. In no-
tillage corn production, glyphosate (840 g ha") applied early preplant consistently provided
at least 94%’late season control which was equivalent to or geater than postemergence
applied nicosulfuron (35 g ha") or primisulfuron (40 g ha“). Early preplant applications of
nicosulfuron or primisulfuron generally provided inadequate control. However, when

applied as a sequential treatment with a postemergence application of atrazine, control

22

23,
increased sigiificantly. Nomenclature: Atrazine, 6-chloro-N-ethyl-N’-(1-methylethyl)-1,3,5-
triazine-2,4-diamine; Glyphosate, N-(phosphonomethyl)glycine; Nicosulfuron, 2-[[[[(4,6-
dimethoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]-N,N-dimethyl-3-
pyridinecarboxamide; Primisulfuron, 2-[[[[[4,6-bis(difluoromethoxy)-2-
pyrimidinyl]amino]carbonyl]amino] sulfonyl]benzoic acid; quackgass, Ebrtrigia repenr (L.)
Nevski #1 AGRRE; corn, Zea mays L.

Additional index words. AGRRE, application timing, atrazine, CGA-136872, cultivation,

DPX-V9360, gowth stage, sequential application.

Introduction

Quackgass is a serious weed problem in northern United States and southern
Canada (13). Its ability to propagate from seed and undergound rhizomes make it nearly
impossible to eradicate (9, 13, 18). Severe quackgass infestations have been reported to
reduce corn gain yields by as much. as 58% (20). The competitive nature of this perennial
weed emphasizes the importance of an effective control progam for successful corn
production in these regions.

The most effective quackgass control progams available for corn production utilize
applications of glyphosate or atrazine. Due to the nonselective nature of glyphosate, it must
be applied prior to crop emergence. Late fall or early spring pre-plow applications will
effectively control actively gowing quackgass which is at least 20-cm in height without soil
activity (8, 9, 12). Many producers have difficulty making timely fall applications due to

inclement weather or delayed harvests. Spring applications may delay corn planting beyond

 

lLetters following this symbol are a WSSA-approved computer code from Composite
List of Weeds. Revised 1989. Available from WSSA, 309 West Clark Street, Champaigi,
IL 61820.

24

optimum dates while waiting for quackgass to reach the desired application stage (18).

Selective quackgass control in corn can be achieved from applications of atrazine.
Optimum control is provided from a pre-plow application of 2.2 kg ai ha'l when followed
with an additional preemergence or postemergence application of 2.2 kg ha’1 (7, 8, 9).
Despite the benefit of postemergence selectivity in corn, atrazine treatments have some
shortcoming. Soil persistence from this treatment will restrict crop rotation to atrazine
tolerant crops the following year (8, 9). These restrictions and recent changes in the
registration status in the United States have reduced the use of atrazine for quackgass
control in corn.

Nicosulfuron and primisulfuron are sulfonylurea herbicides which provide control of
many gass and broadleaf weed species when applied postemergence in corn. These
herbicides provide new alternatives for control of troublesome weed species such as
johnsongass [Sorghum halepens'e (L.) Pers.], shattercane [Sorghum bicolor (L.) Moench], and
quackgass. In soils with a pH of 6.8 or less, these herbicides have a relatively short half-life
and crop rotation is generally not a problem (1, 2).

Several researchers have examined postemergence activity of nicosulfuron and
primisulfuron on quackgass. Quackgass control in excess of 80% has been reported with
both herbicides in conventional tillage corn production (3, 6, 14, 15). However, less than
acceptable control has also been observed (6, 19). Quackgass control was similar regardless
of herbicide rate (4, 19), application timing (4, 5, 15), or use of cultivation (5). However
other researchers found control influenced by rate (4) and application timing (10, 19). Little
research has examined the efficacy of either herbicide in no-tillage corn production.
Primisulfuron did not provide acceptable quackgass control in no-tillage corn production
(11). In the same study, nicosulfuron provided unacceptable early season quackgass

control, but late season control was at least 85 %. Multiple applications of nicosulfuron and

25

primisulfuron were required to provide acceptable johnsongass control in no-till (16).
The objectives of this research are to; a) observe the effect of nicosulfuron and

primisulfuron application rate, application timing, and cultivation on postemergence

quackgass control in corn and, b) compare quackgass control from nicosulfuron,

primisulfuron, and glyphosate in conventional and no-tillage corn production.

Materials and Methods

Research was conducted in mid-Michigan during 1990 and 1991 to examine
quackgrass control in corn. The sites selected had a natural dense quackgass infestation.
All herbicide applications were applied with a tractor mounted compressed air sprayer.
Glyphosate treatments included nonionic surfactant2 (0.5% v/v) and were applied prior to
spring tillage in 70 L water ha" at 234 kPa utilizing 80013 nozzle tips. Nicosulfuron and
primisulfuron applications included petroleum oil adjuvant‘ (1% v/v) and were applied in
206 L water ha‘l at 234 kPa' using 8003’ nozzle tips. All treatments were applied to plots
at least 3-m wide (4 rows) by 10-m in length. Quackgass control and corn injury were
visually evaluated with 0 representing no visible injury and 100 representing complete plant
death. Evaluations were taken in mid July, August, and October.
Effect of application timing. Field trials were conducted in 1990 and 1991 to examine the

effect of application timing and herbicide rate on quackgass control with nicosulfuron and

 

2X-77 nonionic surfactant is a mixture of alkylarylpolyoxyethylene glycols, free fatty acids,
and isopropanol marketed by Valent U.S.A. Corp., 1333 N California Blvd., Walnut Creek,
CA 94596.

3'Teejet flat fan tips. Spraying Systems Co., North Avenue and Schmale Road, Wheaton
IL 60188.

‘Herbimax, 83% petroleum oil, 17% adjuvant, a product of Loveland Industries, Inc. PO
Box 1289, Greeley, CO 80632.

26

primisulfuron in conventional tillage corn production. The soil type at the 1990 site was a
Mariette fine sandy loam (fine-loamy, mixed, mesic Glossoboric Hapludalfs) with 2.0%
organic matter and 4.4 pH. Seedbed preparation consisted of spring chisel plow, disked
twice, then planted with corn variety ‘Maumee Valley 6278’ on May 25. Fertility progam
consisted of anhydrous ammonia applied (134 kg N ha") pre-plow. Starter fertilizer (168
kg ha“, 8% N, 26% P205, 26% K20) was applied in a band below the soil surface at
planting. Fonofos [O-ethyl-S-phenylethylphosphonodithioate] (1.8 kg ha) was applied as a
T-band at planting. Annual weed species were controlled with a preemergence application
ofnetolachlor[2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-l-methylethyl)acetamide]
at 2.2 kg ai ha‘l plus cyanazine (2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl]amino]-2-
methylpropanenitrile) at 2.2 kg ha".

Soil at the 1991 research site consisted of a Colwood-Brookston loam complex
(Colwood, fine-loamy, mixed, mesic Typic Haplaquolis; Brookston, fine-loamy, mixed, mesic
Typic Argiaquolls) with 2.9% organic matter and 6.2 pH. The soil was disked twice prior
to planting corn variety ‘Pioneer 3718’ on May 23. Nitrogen at 128 kg N ha'1 was applied
as 28% liquid urea-ammonium nitrate fertilizer solution (159 L ha") prior to corn
emergence. Annual weed species were controlled with a broadcast preemergence
application of metolachlor at 2.2 kg ha" plus atrazine at 1.8 kg ha".

Nicosulfuron and primisulfuron treatments were arranged as a factorial with three
herbicide rates and three application timings; early, late, and sequential. Early and late
postemergence applications were timed such that quackgass shoots averaged two and four
true leaves, respectively. The shoot height and leaf stage for corn and quackgass at the

time of application is shown in Table 1. Sequential applications consisted of one-half of the

 

 

 

 

 

a: :a $8 5-9. an 6 some...» a: new 2 2:: 3:658

E 3 an 3-2 «mm 5 causes a: was e 2:: son
-- -- a: 5 some...» as 9.... m a: Em 32

6 on $3 3.8 E 5 I a: a-“ a 2:: gsosaom

E 2. 38 8-8 SN 5 Z 33 8-2 : 2:; soc
-- -- 8w 5 3 a: 8-3 8 E3. cam 82
3:7. Susana 35:30

8: 2.» Gt 8-2. am 8 nausea as 9% a 2:; son 25
E m-.. :3 :13 new 5 some...» 85 m3 3 2:: eon. 23m 32

E 3 :9 ”new we 8 an as 3.» nu 2:: ea 23
6 3 G: 3-2 N: 3 4.8.25 3: a-.. 2 as: 58 Sam 82
been ”SE: ecu—woman?

@950— .«O .0: Eu «.8 SOC-am 8‘30— .«O .O: EU
ems” “no.“ 233* .3280 one..." «ecu— Ewmom 2.5 mums—E. 30>
Eco magic—oaac scanning

 

.86on :03 c8 38.—ESE 5v omega use omen.— ofi 88:2: Sat 2: .couonvoa

owe—E 1:85.268 5 ”—3.83% 365.5: 9 coma 58 23 $89.83 .5.“ A852 0:5 093 «no— uca Eamon ace—m

.~ ass

28

total herbicide rate applied early postemergence (EP)5 and the remaining herbicide applied
late postemergence (LP). The interval separating the sequential applications was 9 and 10
days in 1990 and 1991, respectively.

Effect of cultivation. Field experiments were conducted in 1990 and 1991 to examine the
efiect of herbicide rate, application timing, and the use of cultivation in combination with
herbicide treatments for quackgass control. The research sites were adjacent to each other
on a Sisson fine sandy loam (fine-loamy, mixed, mesic Typic Hapludalfs) with 2.9% organic
matter and 6.9 pH in 1990 and 3.1% organic matter and 6.6 pH in 1991. Primary tillage
consisted of spring moldboard plow and chisel plow in 1990 and 1991, respectively. Final
seedbed preparation was accomplished by two passes with a disk. Nitrogen (134 kg ha“)
was applied as urea and incorporated with the final tillage Operation. Starter fertilizer (336
kg ha", 6% N, 24% P205, 24% K20) was band applied at planting. Corn variety ‘Pioneer
3751’ was planted in 76-cm row spacings on May 15, 1990 and May 16, 1991. The entire
research area received a preemergence application of metolachlor at 2.2 kg ha‘1 and
cyanazine at 2.2 kg ha'1 for control of annual weed species.

Nicosulfuron and primisulfuron treatments were arranged in a factorial with three
herbicide rates and three cultivation systems. These systems consisted of the full herbicide
rate applied EP to two-leaf quackgass with and without cultivation and a sequential
postemergence application where one-half of full rate was applied to two-leaf quackgass
and the remaining herbicide was applied approximately 10 days later. Cultivation was
accomplished with a tractor mounted 4-row cultivator‘ equipped with 18-cm wide sweep

shovels operated at a depth of 8 cm. Early preplant (EPP) applications of glyphosate were

 

‘Abbreviations: EP, early postemergence; LP, late postemergence; EPP, early preplant.

‘John Deere Model 875, min-till cultivator with C-shanks. Deere and Company, Moline
IL, 61265- 1304

29'

included with and without cultivation for comparative purposes. The plant heights and leaf
stages for each of these applications are shown in Table 1.

Quackgass control in no-tillage. Quackgass control from glyphosate, nicosulfuron, and
primisulfuron was examined in no-tillage corn production. Research in 1990 was conducted
on a Mariette sandy loam soil with 1.8% organic matter and 4.6 pH. Corn variety ‘Pioneer
3573’ was planted without tillage on May 8 into an area which was previously set-aside.
Starter fertilizer was applied at 224 kg ha'1 (4.5% N, 26% P205, 23% K20) below the soil
surface during planting. The 1991 research was conducted on a Spinks loamy sand (sandy,
mixed, mesic Psammentic Hapludalfs) with 2.1% organic matter and 5.2 pH. Corn variety
‘Pioneer 3718’ was planted without tillage on May 25 into corn residue. In both years,
existing vegetation and annual weeds were controlled with a preemergence application of
metolachlor at 2.2 kg ha'1 plus cyanazine at 2.2 kg ha‘1 plus nonionic surfactant at 0.25% v/v.
This treatment was applied utilizing 28% urea-ammonium nitrate liquid fertilizer (393 L ha'
1) as a carrier.

Nicosulfuron and primisulfuron treatments were arranged in a factorial with two
herbicide rates and four application timings. These methods included early preplant, early
preplant followed with postemergence applied atrazine (1.7 kg ha“) plus petroleum oil
adjuvant (1% v/v), early preplant (one-half the total rate) followed with the remaining
herbicide applied postemergence, and postemergence. All postemergence treatments were
applied when quackgass regowth had reached 2 fully developed leaves. The study included
a standard quackgass treatment consisting of glyphosate (840 g ha") applied early preplant.
The weed and crop stages at the time of application are shown in Table 2.

Data analysis. All studies were conducted as randomized complete block desigis repeated
over time. Treatments were replicated four times in all studies except the cultivation study

which had three replications. Arcsine transformation of all data was conducted prior to

30

 

5 in as 8.2 one 3 nausea 63 a-” 2 2:; 38m

 

 

 

 

-- .. :s E 3 so 3.: R a: mum
-- -- mos 5 some...» as an m a: .Em 33
Soc
5 on as 8-2 5 E G: as a 2:: 053....
“mom
6 m-“ as 3.“ am E E 63 9..» _ as: 833823
-- -- a 5 I 83 ”we 2 a: B:
-- -- an 5 cm as 8-8 R =8... .Em 82
megs— «o .o: :6 c8 mucosa 323— .«c .o: :6
owe... a3 .fism Ease owe... s3 swam 28 mean. 23>
Eco $83030 538:9?

 

.83on some .5.“ 3855.39 .5 owfiga can omen.— ofi 8865 Sun 25.
dozen—coca owe—Eon E 538:9? 2:05an o. coma E8 was $83—an .8.“ A823— 036 own..." E2 can Emma: :85 N finch

31

analysis of variance. Analysis of variance of combined data indicated significant year by
factor interactions in all studies, therefore treatment means for each year are presented
separately. Nicosulfuron and primisulfuron treatment means were separated utilizing
Fishers’ Protected Least Significant Difference at the 5% level of significance. In studies
containing glyphosate as a standard for comparison, Dunnett’s test (P=.05) was used for

comparison of the standard to nicosulfuron and primisulfuron treatments.

Results and Discussion

Effect of application timing. Effective postemergence quackgass control (>75%) was
observed at all herbicide rates and application timings. Nicosulfuron (35 g ha") and
primisulfuron (40 g ha“) generally provided similar quackgass control within a given
application timing (Table 3). The only observed difference in control was in October, 1990
when nicosulfuron provided geater control of four-leaf quackgass than primisulfuron.

The level of quackgass control from either herbicide was dependant upon herbicide
rate. Control increased as nicosulfuron rate increased from 35 g to 70 g ha", but this effect
was observed only from EP applications evaluated in August 1990 and 1991 as well as
October 1991. Quackgass control increased as primisulfuron rate increased from 20 g to
40 g ha“1 in the 1990 gowing season. As with nicosulfuron, control differences due to
primisulfuron rate were observed only at the EP application timing. In 1991, no quackgass
control rate response was observed with primisulfuron. Previous research did not show
differential quackgass response to nicosulfuron rates from 52 g to 104 g ha’1 (19) or from
35 g to 140 g ha'1 when applied to four- to six-leaf quackgass (3). With primisulfuron,
control of four- to six-leaf quackgass has been reported to increase as application rates
increased from 10 to 30 g ha'1 (3).

Differences in quackgass control due to postemergence application timing were

32

083 05 be
«5:28 ecu v.38 e833 23> Benton—Eco .858ch Co :26. can 2: 8 Om.— 38083 {2mm 8 neurones 85v 8: co coau— oES. 2: 55 ESE Eugenio
.3 woman omen 9.39:2 05 new mm com—Eu 3.885 38 05 be

rom .33 Emu—.038 com—Ea .mimm magma—cue: .32 2:3. 2 85908033 22 Riga SA ”832 25.8 9.3826 axons—o 2 859080qu 2.80 voice .mma
.>\> G3 .a Egan—cu ac Eco—9:05. ova—us 35882.?

 

 

 

 

 

 

 

 

 

 

mag 33 we: .18 2.8 2.5 2.8 ea 03 33 38 2.8 8
we: .38 is 38 .32 .2. 9.2a 08 ca 1.3 .38 as 8
3338 mag .88 2.8 .08 38 ca .3 ER 1.8 at 8 5.2.325

«8 38 38 «a .38 .38 38 38 on: sea 2.8 33 2.
38 .18 we: 88 38 3% 2:8 «3 1.3 38 «a new on
e. a a... 8 i 3 o... 8 o... a a 2. o... 8 a a a 8 e... 8 a a a 8 mm 55.382

s 12 a u
Sim .3 mm .155 .5 .5 RES .3 mm Sim .3 mm as. .8398:
2 space a up»: a .8on a was...
aaouaozcma RS aȤ28=&u. 83
9.22.8 9.29930

 

debated E8 095: 35:52.8 5 use: 828:9? 28 33 0203.6: .3 0080...? 8 coca—SEE“ c5 coca—88m: 55 35:8 gnaw 85925.3.— .m. Seek

33

apparent in 1990 and 1991. Nicosulfuron provided greater control of four-leaf quackgrass
(LP) than two-leaf quackgrass (EP) in 1990. This trend was observed at the 35 and 56 g ha"
application rates in August and with all rates in October. Throughout most of the 1991
study, B? and LP application of nicosulfuron provided similar control. Nicosulfuron (35 g
ha") applied sequentially in 1991 provided greater quackgrass control throughout the
growing season than the same rate applied EP. In general, quackgrass control was similar
whether nicosulfuron was applied as a single LP application or as a sequential application
in 1990 and 1991. The only exception was observed in October 1990 when 35 g ha’l applied
LP provided greater control than the same rate applied sequentially.

Application timing had a significant impact on quackgrass control with primisulfuron.
By the end of the 1990 and 1991 season, primisulfuron (20 g ha") provided greater control
of four-leaf quackgrass than two-leaf quackgrass. At higher application rates, control was
similar regardless of leaf stage. Sequentially applied primisulfuron provided greater late
season control than the same rate applied EP in 1990 (20 g or 30 g ha") and 1991 (30 g ha'
1). Regardless of application timing, primisulfuron at 40 g ha“1 provided similar late season
control. In most instances, primisulfuron applied sequentially gave control similar to a single
application to four-leaf quackgrass.

N icosulfuron and primisulfuron provided similar quackgrass control whether applied
with single or sequential applications (5). Conflicting results have been reported regarding
the effect of quackgrass growth stage on control. Late applications of nicosulfuron and
primisulfuron have provided greater control than early applications (19). Despite early
season differences, control of three- to five-leaf or five- to seven-leaf quackgrass was similar
9 weeks after treatment with primisulfuron (5). Similarly, nicosulfuron provided similar
control of one- to three-leaf, four- to six-leaf, and seven- to 10-leaf quackgrass (5).

Quackgrass control was least effective when nicosulfuron and primisulfuron were

34

applied EP at the lowest rates tested. By applying these rates at the LP timing, one could
expect quackgrass control equivalent to higher rates applied EP. This approach could be
used to reduce the amount of herbicide used, thus reducing weed control costs.

Efl'ect of cultivation. Postemergence application of nicosulfuron (35 g ha") and
primisulfuron (40 g ha") provided mid-season quackgrass control equivalent to or greater
' than that provided by early preplant glyphosate (840 g ha“) applications (Table 4).
Cultivation of these treatments provided similar or greater quackgrass control than the same
treatments without cultivation. At harvest, nicosulfuron and primisulfuron treated plots with
or without cultivation had quackgrass control and corn yields similar to glyphosate treated
plots with or without cultivation.

Postemergence quackgrass control was at least 88% with nicosulfuron in both 1990
and 1991 (Table 4). No differences in quackgrass control or corn yield were observed as
' nicosulfuron rates increased from 35 g to 70 g ha“1 regardless of cultivation. With
primisulfuron, control ranged from 77% to 98% depending upon herbicide rate and
cultivation. Mid-season quackgrass control increased as primisulfuron rate increased from
20 g to 40 g '1 in 1990 cultivated treatments and both with and without cultivation in 1991.
No differences were observed in late season control or corn yield due to primisulfuron rate.

Sequential applications of nicosulfuron or primisulfuron provided equivalent or
greater midseason control than the same rate applied EP with or without cultivation. The
use of cultivation 10 days after nicosulfuron or primisulfuron application resulted in similar
or greater control than the same treatment without cultivation. With the exception of
primisulfuron in 1991, all treatments, regardless of cultivation resulted in similar late season
quackgrass control and corn yields. In 1991, primisulfuron applications combined with
cultivation provided greater quackgrass control at harvest than the same treatment without

cultivation. Corn yield in plots receiving primisulfuron (20 g ha") and cultivation was

35'

49.6. 3.: 05 8 82 8.88550 .3 vouch—808v 8 5:28 2:8 2: £53 88225» 58.. .5850 98 C 55 v0.2.3 882: .558; .25. 5:383 :25 a he
8:: 93 85:28 .8253 38> 23.5950 3:85:38 he .96— .Rm 2: 8 Ovi— 38893 8.80:8.» 8 9.5.83 8% .e: on .632 058 05 55 33:. .5582?
.822 «5 3 conga 8.8 9.2862 2: 55 995. 588:9? 0.9.8 05 8 com—Ea 22 3.865 05 no 8082. Damn

.>\> 8m... 8 2888.58 85:8: Bus—us Eon—.8... 89.2.50 .>\> 8: 8 395?.“ no 83.8.2— 332: 8:253... 5:53:58. 23 coca—3°32-

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

..8: :8: 8 8 8 8 :8 2.3.8.0

9.38: 9.28: 3:8: 38 a8 2.8 «8 .8 8.8 8

3 2...: 8 an: 3 8‘: 8 8 a 8 u... 8 8 8 u.“ 8 a. 8 8
o 89: 8 :88 3 :88 o 8 3 8 +3 R m... 8 3 8 m 8 8 83:83:

a 88_ a. an: a 888 a 8 a 8 a 8 a 8 8 8 a... 8 8

8 88" 3 c8: 3 :8: a 8 a.“ 8 3 8 8 8 3 8 E 8 8
a 88" 8 88" 3 8:: a 8 8 8 a 8 a 8 o... 8 E. 8 8 5.3.382

88

85 on: 8 8 8 8 38 289.86

a 88 8 888 a 85 8 8 a 8 a 8 a.“ 8 .a 8 .f. 8 8

8 82: a 8:: an 88” a 8 a 8 8 8 .Z 8 .2. 8 ._.o 8 8
a. 82: a :8: a. :88 8 8 8 8 a 8 3 8 .3 8 E 8 8 8.3.385

a 85 a 2:: a 88: no 8 a 8 a 8 . 9a 8 .3 8 8 8 8

8 8:: 8 8:: a. 8:: a 8 8 8 8 8 3 8 8 8 E 8 8
8 888 a an: a 88: e 8 8 8 8 8 a.» 8 .86 8 _ 8 8 53382

88
.2 9. 8 vs. 8 u
. + - - + - - + - 2.8 .8895:
. and“ 558:8? a 5:829? a 528:9?
3.588 288 3.588 288 8.588 288
8885 £553 8:380
so; 5.8 58 2 .328 2 8....
9.22.8 839—850

 

.Eeo own—E 8:32.288 5 38:8 gnaw no 5:323 28 $58: grooming .32 3858.: He Soho 2F v ~35

36

greater than the yield from sequential application of the same herbicide rate.

The utility of cultivation in combination with postemergence nicosulfuron and
primisulfuron applications has been previously examined. Quackgrass control was not
increased by hand cultivation 4 weeks after primisulfuron application (5). However,
cultivation following nicosulfuron application increased johnsongrass control compared to
treatments not receiving cultivation (17). These results concur with our findings. Generally
quackgrass control was similar or greater with cultivation in early season evaluations,
however, late season control was generally similar regardless of cultivation.

Quackgrass control in no-tillage. Nicosulfuron and primisulfuron applications provided
quackgrass control ranging from 15% to 98% depending upon application timing (Table 5).
Increasing the application rate of either herbicide generally did not improve quackgrass
control from either sequential or single postemergence applications. However, increasing
herbicide rate in single early preplant (EPP) applications generally increased quackgrass

control. -

Application timing influenced nicosulfuron and primisulfuron efficacy. With the
exception of nicosulfuron in 1990, single EPP applications of either herbicide generally
resulted in less quackgrass control than other application timings. Control from EPP
treatments generally increased when followed with a postemergence application of atrazine
(1.7 kg ha") or a postemergence application of additional nicosulfuron or primisulfuron.
Primisulfuron (40 g ha") applied EPP gave less than 45% control in both years (Table 5).
By following this EPP treatment with a postemergence application of atrazine to two-leaf
regrowth, full season quackgrass control was increased to at least 85%. Sequential
application (EPP followed by POST) of primisulfuron (40 g ha") provided greater full
season quackgrass control ( z 71%) than the same primisulfuron rate applied early preplant

(<45 ‘70). Similar results were observed with sequential nicosulfuron applications and EPP

37

:26. mod 0:. 3 82 58:55 .3 cos—583 8 :828 0:8. 05 £55 282:5» ES: .585: 2a a 55 38:0: 83:. :86325. .25: 523.26 :03» a u:

2.8. :5 325.8 5250: 23> 3035—68 3:85.»? a: .26. awn 0:. 3 Q3 v0.3.2: {oi—L 2 9:280: 8.5: 3: on 3:2 2:8 0:. 5m) 23:. .558»?
3:090:8qu com—go

E; *5 25.6.. a. 58.8.2. 3: f... 9. Ev 05:5“ 55 83:2 2m 8%.: 8.865 28 gig: "85:8603: 83% 8382. 9.3.5. 3 83:8
22:2: 2.80 Bag: 08835 38 $8 2.3.5.59. BEE: Fag—3mm 59362.8.— .85906033 :5 .532: 2.80 com—Eu 28.83% 2&5». .59— 05 mama
.>\> Quad 8 .588...“ 3:35: 80205 32:38. 280ng .>\> $3 8 395?: ac Sac—8.2. 3295 8:08:85 53:33:.— vg 53:382-

 

 

 

 

 

 

 

 

 

 

 

 

 

a 8 8a 232an
£8 3:: £2 .wox. .38 £8 38 .59 8
a. S a... g .3 an .u 8 a... 3 u... a .3 n .= 8 8 8.2.325
as «8 2.8 .38 38 «a .38 .38 2
a 8 a B a... 2. .m a .3 8 as a .3 2. .3 8 mm 8.3.382
as
a 8 3w 282.50
.38 .08 .8: L8 33 38 a8 :8 8
3 8 .o 8 .o 8 L 2 3 8 .o 8 .8 a .w a. 8 5.3.3.5.:
«3 2.8 38 £8 «8 a8 «a £8 E
o... B .8 S 3 8 .1. S 3 a u... a a a .I. a 2 85.382
as
«my . :2. mu m
#55:: .50.. Schmmm Em Ekimm .52 Sofifim Em 2a: .335:
amps—E: 528:9? swig. :o_~8=&<
2 .330 8 2.:
L828 389.350

 

£262.93 E8 own—div: 5 9:8: 538:9? :5. 2.: 0203.8: .3 cocoa: 8 33:8 8393.30 .n 8a.:

5

38

followed by postemergence applied atrazine combinations in 1991. Single postemergence
applications provided late season control ranging from 82 to 90% for nicosulfuron and 60
to 78% for primisulfuron. Control from these postemergence applications was equivalent
to or greater than combination treatments applied early preplant and postemergence.

_ Early preplant application of glyphosate (840 g ha") consistently provided at least
94% quackgrass control in no-tillage corn production (Table 5). This level of control was
superior to early preplant applications of nicosulfuron (1991) and primisulfuron (1990 and
1991). The rate of glyphosate activity was much greater than either of the sulfonylurea
herbicides. By three weeks after treatment, quackgrass treated with glyphosate was
completely necrotic. During the same interval, quackgrass treated with nicosulfuron or
primisulfuron ceased growing but had not developed necrotic symptoms.

Midseason quackgrass control from nicosulfuron (35 g ha") and primisulfuron (40

3 ha") applied postemergence was comparable to that obtained with glyphosate. Late
season control from the postemergence applied sulfonylureas was less than glyphosate in .
1990 and equivalent to glyphosate in 1991. Glyphosate consistently gave excellent full season
control of quackgrass sod in no-tillage corn production. Postemergence applications of
nicosulfuron and primisulfuron also provided control of quackgrass, however their

performance was not consistently as effective as glyphosate.

Acknowledgements
The authors would like to thank CIBA-GEIGY and 13.1. DuPont for their product
donations and financial support of this research. Our sincere gratitude is expressed to A.

Chomas, C. Sprague, J. Schmidt, and J. B. Carey for their assistance in this research.

10.

11.

12.

13.

1.4.

15.

Literature Cited

Anonymous. 1988. BeaconTM Herbicide. Technical Release. Agricultural Division,
CIBA-Geigy Corporation, Greensboro, NC. 8 p.

Anonymous. 1990. AccentTM Herbicide. Technical Bulletin. E. I. du Pont de
Nemours and Co. Inc., Agricultural Products Dep., Wilmington, DE. 12 p.

Bhowmik, P. C. and B. M. Bahnson. 1989. Postemergence activity on DPX-V936O
and CGA-136872 in controlling quackgrass [Agmpymn repens (L.) Beauv.] in corn.
Abstr. Weed Sci. Soc. Am. 29:2-3.

Bhowmik, P. C. and B. M. Bahnson. 1990. Postemergence quackgrass [Eb'nigia
repens (L.) Nevski] control in corn. Abstr. Weed Sci. Soc. Am. 30:5.

Bhowmik, P. C. and B. M. Bahnson. 1990. Quackgrass control in field corn with
CGA-136872 and DPX-V9360. Proc. Northeast Weed Sci. Soc. 44:86.

Bruce, J. A. and J. J. Kells. 1988. Quackgrass (Agropyron repens (L.) Beauv.) control
in corn with selective postemergence herbicides. Proc. North Cent. Weed Control
Conf. 43:33. '

Buchholtz, K. P. 1963. Use of atrazine and other triazine herbicides in control of
quackgrass in corn fields. Weeds 11:202-205.

Doll, J. D. 1981. Quackgrass control in field crops. University of Wisconsin
Cooperative Extension Bull. no. A2045.

Fawcett, R. S. and V. M. Jennings. 1978. Quackgrass and its control. Iowa State
University Cooperative Extension Bull. no. Pm-742.

Gillespie, G.R., PJ. Porpiglia, and J.W. Peek. 1990. Influence of application
variables on the herbicidal activity of CGA-136872. Abstr. Weed Sci. Soc. Am. 30:6.

Hahn, R. R. 1990. Quackgrass control programs for field corn. Proc. Northeast
Weed Sci. Soc. 44:87.

Ivany, J. A. 1981. Quackgrass (Agropyron repens) control with fall-applied
glyphosate and other herbicides. Weed Sci. 29:382-386.

Mitich, L. W. 1987. The Devil’s grass: quackgrass. Weed Technol. 1:184-185.
Moses, A. J., C. L. Kern, T. B. Threewitt, D. E. Stamm, T. D. Taylor, M. D.
Johnson, J. Cantwell, T. R. Dill, and G. R. Gillespie. 1989. Summary of the 1989
CGA-136872 EUP program. Proc. North Cent. Weed Sci. Soc. 44:36.

Reinhart, M. W., M. J. Dobrotka, and S. W. Rowe. 1989. DPX-V9360 performance
on difficult to control grass species in corn. Proc. North Cent. Weed Sci. Soc. 44:30.

39

16.

17.

18.

19.

20.

40

Ross, M. A. 1989. Selective control of johnsongrass [Sorghum halepense (L.) Pers.]
in corn. Proc. North Cent. Weed Sci. Soc. 44:40-41.

Worthington J. P. 1990. The effect of cultivation preceding herbicide application
of DPX-V9360, DPX-79406 and CGA-136872 on control of johnsongrass [Sorghum
halepense (L.) Pers.] in corn. Proc. North Cent. Weed Sci. Soc. 45:34-35.

Wyse, D. L. 1976. Quackgrass control in field crops. Proc. North Cent. Weed
Control Conf. 31:152-154.

Yenish, J. P. and J. D. Doll. 1990. Efficacy of CGA-136872, DPX-V9360, and DPX-
79406 on quackgrass (Agropyron repens (L.) Beauv.) control in corn. Abstr. Weed
Sci. Soc. Am. 30: 5.

Young, F. L., D. L. Wyse, and R. J. Jones. 1984. Quackgrass (Agropyron repens)
interference on corn (Zea mays). Weed Sci. 32:226-234.

CHAPTER 3

ADJUVANT EFFECT ON ABSORPTION AND ACTIVITY OF NICOSULFURON AND

PRIMISULFURON IN QUACKGRASS [Emu m (L.) Nevski]

ABSTRACT

Greenhouse and field experiments were conducted to determine foliar absorption
and activity of nicosulfuron and primisulfuron by quackgrass with various adjuvants. Foliar
absorption of l‘C-nicosulfuron and l‘C-primisulfuron plus petroleum oil adjuvant (POA) was
completed by 4 hours after application. Absorption of nicosulfuron and primisulfuron plus
POA increased from 11 and 2% of applied, respectively, to 51 and 12% with the addition
of 28% urea-ammonium nitrate liquid fertilizer (UAN) at 4% v/v. At least 83% of the
absorbed 1‘C from either herbicide penetrated the leaf epicuticular waxes. Absorption of
1‘C-labeled herbicides was greatest with the following adjuvants: POA + UAN > nonionic
surfactant (NIS) at 0.25% v/v + UAN = methylated seed oil at 0.75% v/v. The addition
of UAN to either NIS or POA significantly increased 1“C-herbicide uptake. In greenhouse
studies, nicosulfuron (35 g ai ha") and primisulfuron (20 g ha") applied with POA plus
UAN provided greater quackgrass control than with POA alone. Despite the differences
in foliar uptake in the greenhouse, few differences were observed between these adjuvants
in 1989 or 1990 field efficacy trials. Quackgrass control was reduced by the addition of
atrazine (1120 g ha“) to nicosulfuron plus POA in 1989 and to primisulfuron plus POA in
1990. Combinations with atrazine did not reduce “C-nicosulfuron or “C-primisulfuron
uptake by quackgrass. Nomenclature: Atrazine, 6-chloro-N-ethyl-N’-(l-methylethyl)-l,3,5-

triazine-2,4-diamine; Nicosulfuron, 2-[[[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]amino]

41

42
sulfonyl]-N,N-dimethyl-3-pyridinecarboxamide; Primisulfuron, 2-[[[[[4,6-bis(difluoromethoxy)-
2-pyrimidinyl]amino]carbonyl]amino] sulfonyl]benzoic acid; quackgrass, Elytrigia repens (L.)
N evski #1 AGRRE.

Additional index words. AGRRE, antagonism, CGA-136872, DPX-V9360.

INTRODUCTION

Effective adjuvants enhance foliar penetration, increase foliar retention of spray
solution, and improve spray delivery (20). Not all adjuvants improve herbicide efficacy and
some can even reduce efficacy (25). The effectiveness of an adjuvant can be very specific.
Several researchers have observed that adjuvant efficacy is dependant upon the herbicide
being applied and the characteristics of the target weed species (9, 14, 23).

Nicosulfuron and primisulfuron are new sulfonylurea herbicides which control many
grass and broadleaf weed species when applied postemergence in corn (Zea mays L.) (1, 2).
These herbicides provide alternatives for control of troublesome weed species such as
Johnsongrass [Sorghum halepense (L.) Pers.], shattercane [Sorghum bicolor (L.) Moench],
and quackgrass. The use of nonionic surfactant (NIS)2 or petroleum oil adjuvant (POA)
is recommended to improve nicosulfuron and primisulfuron efficacy (1, 2).

Quackgrass is a serious weed problem in northern United States and southern
Canada (15). Quackgrass with its underground rhizomes is a perennial that is nearly
impossible to eradicate (26). Despite these traits, several researchers have reported

acceptable (280%) quackgrass control from postemergence applications of nicosulfuron or

 

1Letters following this symbol are a WSSA-approved computer code from Composite
List of Weeds. Revised 1989. Available from WSSA, 309 West Clark Street, Champaign,
IL 61820. -

2Abbreviations: NIS, nonionic surfactant; POA, petroleum oil adjuvant; UAN, 28%
urea-ammonium nitrate liquid fertilizer; MSO, methylated seed oil.

43

primisulfuron (4, 6, 18, 22). However, less than acceptable control has also been observed
(5, 27). It may be possible to increase quackgrass control through the use of adjuvants
which increase nicosulfuron and primisulfuron absorption.

Foliar absorption of sulfonylurea herbicides by target weed species is often quite low.
Absorption of thifensulfuron (3-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]
amino]sulfonyl]-2-thiophenecarboxylic acid) plus NIS in velvetleaf (Abutilon theophrasti
Medicus) was 15%, 24 hours after application (3). The addition of 28% urea-ammonium
nitrate liquid fertilizer (UAN) to this treatment not only increased absorption to 38% but
also improved velvetleaf control. Fielding and Stoller (10) observed 21% chlorimuron (2-
[[[[(4-chloro-6-methoxy—2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]benzoic acid) uptake
in velvetleaf with NIS and 32% with NIS plus UAN 84 hours after treatment. In field
studies, chlorimuron plus NIS and UAN provided greater velvetleaf control than
chlorimuron plus NIS. Absorption of nicosulfuron and primisulfuron was only 12% and 3%,
respectively, when applied with NIS (7). In field and greenhouse research, nicosulfuron
activity on green foxtail [Setaria viridis (L.) Beauv.] was dependant upon adjuvant (19). The
identification of efficacious adjuvants for use with nicosulfuron and primisulfuron may
increase quackgrass efficacy and consistency.

The weed spectrum controlled by nicosulfuron and primisulfuron can be broadened
through tank-mix combinations with other herbicides. These combinations are of particular
interest to achieve single application, total postemergence weed control. Preliminary
research on nicosulfuron and primisulfuron combinations with atrazine provided equivalent
or greater quackgrass control than similar treatments without atrazine (5). However, activity
on velvetleaf (8) and giant foxtail (16, 17, 21) was reduced when applied in tank-mix
combinations with atrazine. Similar results were observed with giant foxtail (8, 12, 13),

shattercane (11), and velvetleaf (12) control with primisulfuron. Nicosulfuron and

44

primisulfuron combinations with atrazine would be useful for total postemergence weed
control in corn; however, research is needed to identify possible tank-mix interactions which
may potentially reduce quackgrass control.

Our objectives were: a) to examine foliar absorption of nicosulfuron and
primisulfuron in quackgrass, b) to quantify foliar absorption as influenced by adjuvants, and
c) to examine nicosulfuron and primisulfuron efficacy on quackgrass as affected by

adjuvants.

MATERIALS AND METHODS
Greenhouse research. Greenhouse studies were conducted to examine the effect of
adjuvants on foliar herbicide absorption and quackgrass control. Environmental conditions
were maintained at 25 C t 4 C, and plants were grown in a 16-h photoperiod of natural and
supplemental metal halide lighting with a midday photosynthetic photon flux density of 1000
[E m2 s". A rhizome from a slightly pubescent quackgrass biotype was selected from a
field in Williamston, MI. This biotype was then used as a propagation source to maintain
genetic uniformity among plants. All quackgrass plants were raised from single unbranched
three-node rhizome segments placed at a 2-cm depth in l-L plastic pots containing potting
medium’. Plants were watered as needed and fertilized weekly with 50-ml of water soluble
fertilizer solution (400 ppm N, 400 ppm P205, 400 ppm K20). Once plant growth averaged
five-true leaves, the plants were clipped back to the soil surface. Herbicide treatments were
applied to quackgrass regrowth averaging three-true leaves. Powdery mildew and aphid
infestations were controlled with foliar applications of triadimefon [1-(4-chlorophenoxy)-3,3-

dimethyl-1-(1H-1,2,4-triazol-1-yl)-2-butanone] and acephate (0,5-dimethyl

 

3Baccto Professional Planting Mix. Michigan Peat Company, P O Box 980129, Houston,
TX 77098.

45

acetylphosphoramidothionate), respectively.

Foliar absorption of l‘C—nicosulfuron and 14C—prirnisulfuron was measured over a 24-
h period. Herbicide treatments were prepared utilizing 2-pyrimidine l‘C-nicosulfuron (2.3
MBq mg" specific activity, 98.8% purity) and phenyl labeled l‘C-primisulfuron (1.9 Mbq mg"
specific activity, and 97.2% purity). Purity for both herbicides was determined by high-
performance liquid chromatography.

Radiolabeled nicosulfuron was dissolved in tetrahydrofuran. Herbicide stock solution
was placed in a vial to prepare a 185 Bq pl" treatment solution. Tetrahydrofuran was
evaporated from the nicosulfuron treatment solution using a nitrogen stream and then
replaced with deionized water. The treatment solution was supplemented with deionized
water, formulated nicosulfuron product,‘ formulation blank, and POA’ at 1% v/v. Final
treatment concentrations were 415 umol nicosulfuron plus 57 mg L" formulation blank.
These treatment concentrations correspond to a field application of 35 g ai ha" applied at
206 L ha".

Radiolabeled primisulfuron was dissolved in methanol and utilized to prepare a 185
Bq pl" treatment solution. This solution was supplemented with deionized water,
formulated primisulfuron product,‘ formulation blank, and POA at 1% v/v. This treatment
contained 207 mol primisulfuron and 32 mg L" formulation blank and less than 10% v/v
methanol. The primisulfuron concentration corresponds to a field application of 20 g ai ha"

applied in a 206 L ha" carrier volume. Quackgrass plants with three fully developed leaves

 

‘Accent 75 WDG herbicide. E.I. DuPont deNemours and Co., Wilmington, DE 19898.

’Herbimax, 83% petroleum oil, 17% adjuvant, a product of Loveland Industries, Inc. PO
Box 1289, Greeley, CO 80632.

‘Beacon 75 WDG herbicide. CIBA-GEIGY Corp., Agricultural Division, Greensboro,
NC 27419.

46

per culm were selected to receive l“C--labeled treatments. A single 2-ul droplet of treatment
solution containing 370 Bq was placed on the adaxial surface of the youngest fully developed
leaf with a microsyringe. The droplet was placed laterally between the leaf margin and
midrib, midway between the base and tip. Herbicide absorption was quantified at 0, 2, 4,
8, 12, and 24 h after herbicide application. At the appropriate harvest interval, the treated
leaf was excised and rinsed in 3 ml methanol for 45 s to remove unabsorbed 1‘C. The
methanol wash vials received lS-ml scintillation cocktail and were quantified by liquid
scintillation spectrometry correcting for quench.

Herbicide distribution in leaf components. Labeled nicosulfuron and primisulfuron treatment
solutions were prepared with the adjuvants POA (1% v/v) or POA plus UAN (4% v/v), and
quackgrass plants were treated as previously described. Six hours after application, the
treated leaf was excised and washed 45 s in 3 ml methanol to remove unabsorbed 1‘C. The
leaf was then immersed in 3 ml chloroform for 10 s to remove epicuticular waxes in the
treated region. The treated leaf was then frozen. The chloroform wash was reduced to near
dryness with a stream of nitrogen. Each methanol and chloroform leaf wash vial received
15 ml scintillation cocktail. Frozen treated leaves were combusted in a biological sample
oxidizer using a mixture of carbon dioxide absorbent and scintillation fluid (1:2 ratio) to trap
evolved 1‘C02. All samples were then quantified by liquid scintillation spectroscopy.
Effect of adjuvant: an absorption Labeled nicosulfuron and primisulfuron solutions were
prepared with each of the following adjuvant combinations; none, NIS7 at 0.2% v/v, POA

at 1% v/v, UAN at 4% v/v, NIS plus UAN, POA plus UAN, methylated seed oil8 (MSO)

 

7X-77 nonionic surfactant is a mixture of alkylarylpolyoxyethylene glycols, free fatty acids,
and isopropanol marketed by Valent USA. Corp., 1333 N California Blvd., Walnut Creek,
CA 94596.

I’Scoil, a methylated seed oil product of AGSCO, Inc. Box 458 Grand Forks, ND 58206.

47

at 0.7% v/v, and atrazine9 plus POA (1120 g ha" + 1% v/v). Treatments were applied to
quackgrass leaves as previously described. Upon drying, calipers were used to measure
droplet spread on the leaf surface. At 1 and 6 hours after treatment, treated leaves were
excised and washed in methanol as previously described to remove unabsorbed “C. Samples
were then quantified with liquid scintillation spectroscopy as previously described. Foliar
absorption was calculated as the difference between total “C applied and the “C recovered
in the methanol wash quantity divided by total applied. Absorption data for both herbicides
were analyzed by nonlinear regression to generate response curves.

Herbicide ejficacy. Nicosulfuron (35 g ha") and primisulfuron (20 g ha") were applied with
the adjuvants POA (1% v/v) and POA plus UAN (1% + 4% v/v). Treatments were
applied to quackgrass regrowth averaging three-leaf and 15 cm utilizing a single 8001Blo
flat fan nozzle on a continuous link-belt sprayer delivering 206 L ha" at 138 kPa. Control
was visually evaluated 30 days after treatment.

Field research. Quackgrass control from postemergence applications of nicosulfuron and
primisulfuron as affected by adjuvants was examined in central Michigan during 1989 and
1990. The selected research sites were infested with a dense quackgrass sod. The 1989
research site had a Parkhill loam (Fine-loamy, mixed, nonacid, mesic Mollic Haplaquepts)
soil containing 3.2% organic matter and a pH of 6.2. In 1990, the soil type was a Sims silty
clay loam (Fine, mixed, nonacid, frigid Mollie Haplaquepts) with 2.3% organic matter and
a pH of 5.6. Spring tillage consisted of moldboard plow, followed by one disking in both
years. Corn (Zea mays L.) varieties ‘Golden Harvest 2300’ and ‘Great Lakes 579’ were

planted on May 23, 1989 and May 30, 1990, respectively. Corn was planted at a population

 

9Aatrex 4L, CIBA-GEIGY Corp., Agricultural division, Greensboro, NC 27419.

10Teejet flat fan tips. Spraying Systems Co., North Avenue and Schmale Road, Wheaton
IL 60188.

48

of 54,000 seeds ha" in rows spaced 97 cm apart in both years. Herbicides were applied to
plots four rows wide by at least 7.6 m long with a tractor-mounted compressed air sprayer
calibrated to deliver 206 L ha" at 207 kPa using 800313 flat fan nozzles. Annual weeds were V
controlled with a preemergence application of metolachlor [2-chloro-N-(2-ethyl-6«
methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] at 2.2 kg ha" plus cyanazine [2-[[4-
chloro-6-(ethylamino)-1,3,5-triazin-2-yl]amino]-2-methylpropanenitrile] at 2.2 kg ha".
Postemergence herbicides were applied to quackgrass averaging four visible leaves (three-
true leaves) and 19 cm in height on June 18, 1989 and 23 cm in height on June 25, 1990.
Quackgrass density averaged 323 and 237 shoots m'2 in 1989 and 1990, respectively.
Quackgrass control and corn injury were evaluated visually with 0 representing no visible
injury and 100 representing complete plant death. Evaluations were made 30 and 60 days
after treatment, mid-October, and 1 year after treatment.

Data analysis. Each greenhouse and field study was conducted as a randomized complete
block design repeated over time. Treatments in all studies were replicated four times with
the exception of the 1990 field study which contained three replicates. Analysis of variance
indicated no significant repeat by factor interactions in greenhouse studies, therefore means
presented are a combined average of the repeats. Field results are presented separately for
each year due to year by factor interactions. Mean separations were determined utilizing

Fishers’s Protected Least Significant Difference at the 5% level of significance.

RESULTS AND DISCUSSION
Herbicide absorption. Foliar absorption of “C-nicosulfuron and 1‘C-primisulfuron with
POA over a 24-hour period is shown in Figure 1. Nicosulfuron and primisulfuron
absorption was characterized by the equations Y = -23.26 em‘x + 23.33 (R2=0.85) and Y

= -30.24. e"'“" + 30.25 (R2= 0.82), respectively. The rate of absorption was greatest during

49

 

 

   
 

 

 

 

 

40
g L A
._ R2 =
LA 6
0'0
8.2 J R2 = .85
08—— ”"_—___-—___-——’—-_-—_-_-__o
(1) _ o
E O 20
2‘6
8 . . ~
ob .
_C
| 10—
to
Primisulfuron + POA _ BX h
- Nicosulfuron + POA Y _ BO e ' + 82
O I I T I r l ' l 1 l . l
O 4 8 12 16 20 24
Time after treatment (h)
Figure 1. F oliar absorption of “C-nicosulfuron and “C-primisulfuron by quackgrass.

Treatments included “C-nicosulfuron and “C-primisulfuron plus petroleum
oil adjuvant (POA) at 1 % v/v.

50

the first 2 hours after application. Nicosulfuron and primisulfuron foliar absorption
approached 23 and 29% of applied, respectively, within 4 hours after application. Foliar
absorption at later intervals was not significantly greater than at 4 hours after application.
These results indicate that the first 4 hours after application are critical for the absorption
process of nicosulfuron and primisulfuron in quackgrass. Nalewaja et al. (19) examined
simulated rainfall effects on nicosulfuron control of green foxtail. They observed significant
reduction in control from rainfall within 1.5 hours after nicosulfuron application. After 3
hours, only slight reduction in control was observed. These results closely parallel “C-
nicosulfuron absorption patterns in this study where foliar absorption was nearly completed
4 hours after application. This would indicate that a 4 hour rain-free interval after
application would be critical for optimum quackgrass control.

Since foliar herbicide absorption approaches a maximum within 4 hours after

treatment, all other absorption studies were quantified 6 hours after application to
approximate maximum foliar uptake.
Herbicide distribution in leaf components. Following application of “C-herbicide, unabsorbed
“C was quantified using a methanol leaf wash. This process removed herbicide remaining
unabsorbed on the leaf surface. The use of a methanol leaf wash does not remove “C-
herbicide which may be retained within the epicuticular waxes of the leaf. A 5- to 10-s
chloroform wash has been utilized to dissolve epicuticular waxes and to remove herbicides
retained in this region (3). A preliminary study with quackgrass indicated that a 10-s wash
interval was appropriate for removing the epicuticular waxes (data not reported). This
interval did not extract chlorophyll from the leaf proper since no green pigments were
detected in the solution. Combustion of the leaf in a biological oxidizer represented the
amount of “C which passed through the cuticle.

The amount of unabsorbed herbicide recovered (methanol wash) was greatest when

51
either herbicide was applied with POA (Table l). The unabsorbed “C in the nicosulfuron

plus POA treatment was 89% compared to only 49% when UAN was added to the
treatment. With primisulfuron plus POA, 98% of the applied “C remained on the leaf
surface compared to 88% when POA plus UAN was used. Enhanced herbicide absorption
was previously reported from the addition of UAN to NIS with thifensulfuron on velvetleaf
(3, 9).

Small quantities of “C-nicosulfuron or “C-primisulfuron were measured in the
chloroform leaf wash component (Table 1). Radioactivity recovered in the chloroform wash
was greatest with treatments containing UAN plus POA. The majority of the leaf absorbed
“C moved through the epicuticular waxes removed by the chloroform wash, regardless of
adjuvant used. Greater than 83% of the absorbed herbicide was recovered in the leaf
combustion fraction. These results indicate that quackgrass leaf epicuticular waxes do not
represent an impermeable barrier to nicosulfuron or primisulfuron absorption into the leaf.
It also confirms that methanol leaf wash techniques provide a good measure of foliar
herbicide absorption.

Total “C recovery in this study was consistently greater with herbicide treatments
containing POA than treatments containing POA plus UAN. Reduced “C recovery with
the use of POA plus UAN may be due to greater herbicide translocation from the treated
leaf than with POA alone. Fielding and Stoller (9) observed greater absorption and
translocation of thifensulfuron with NIS plus UAN than with NIS alone.

Efiect of adjuvants an absorption. Nicosulfuron and primisulfuron absorption results were
very inconsistent when applied without an adjuvant or with UAN alone (Table 2). These
inconsistencies were due to solution surface tension properties and the application technique
utilized. The epicuticular waxes on quackgrass foliage make the leaf very difficult to wet

(24). These characteristics made the application of “C-solutions containing UAN or no

52

6303.5: 08% 2: Ho 2.838 5.33 2.5» 88138009
45:53.. coca 98c on beams—gm»

donate“ Est: 88:: EB:oEEa-ao.5 sewn u Z<D .Egaom mo 8:20on u <0?

 

 

 

 

v a. I. m Jan—3
mm 3 w 3 mm 3. + 3 Z<D + <Om
mm. 2: N 2. no A: <Om
9.2 a m as 8.3355
h o 3 w ".894
am om mm 9m av 3. + A: Z<D + «On
3. on o N." am o4 <9—
9h: 3 w 3 555382
e Bias co e >\> s
.828 Eon. 53388 :33 :33 8mm 5.280830;
889—030 .83 E80820 35522

 

838%..." .2: 952. e - 5,82 0..

 

.255?“ .3 cognate an

83:52» 2: 5 .6830 02035: new Seasons—co .30— mmfiwv—oazc Boa eccaaammEmEO: new =05:38E.U= .«o bo>ooom .~ «335

53

.8838 8:33 33> 88383800..
80880: 88.8 93% am 38395“...
Ava—5:8? 0: 88: A0: 333 398508 - tom—mam U: 1385 .. 3: an 33:38 8.5me
63883 n MH< .30 noon 3.3.3508 n
OmE .uofiatou 2:3— 8838 835888.82: «gm u Z<D 833.3 :0 8:20on u <8 8803.3 08080: n m2 $895.85

 

 

 

 

dz m 3 a h u.@.d3
ow am «.3 2 a 3 + 13 w on: <Om + .mp3.
ow -- mi R 3 he Om:
an 3 Q: 3. mm 3. + o; Z<D + <Om
mm mm «.2 on 3 3. + N6 725 + $2
on -- me o o 3. Z<D
3w 3 03 2 o cg <Om
S 3 QB _ S 2 ad mHZ
ow ww Wm H N" -- 252

5.8— 8 m a 808.33ng

-.... ..... - § -----..---- 88 - ..... o5 ----..... >\> 05

82 $2 .205“... 952 o .8: _ 2.8 .9556...

3an .

L888 889—230 gov—Sm: U: hum—om

 

5:33.? 83.38
.38.." .3 @80on 3 8838808 no .6850 30m 88 8:03:02» 05 8 889.035 .3 8833:8390: we 802903“ 830m .N figs

54

adjuvant very difficult. Once droplets were applied to the leaf surface, they were very easily
displaced. All other adjuvants modified droplet surface tension properties sufficiently to
improve leaf retention, thus improving consistency of treatment results.

Foliar absorption of 1‘C-nicosulfuron and l‘C-primisulfuron was measured at l and
6 hours after application with eight different adjuvant combinations. Nicosulfuron
absorption in quackgrass ranged from 0 to 40% of the total 1‘C applied (Table 2). At 1
hours after application, nicosulfuron absorption was greatest with POA plus UAN (33%)
followed by NIS plus UAN (24%). At 6 hours after application, absorption with POA plus
UAN increased to 40%, greater than either NIS plus POA (30%) or methylated seed oil
(M80) (27%).

Foliar absorption of primisulfuron in quackgrass ranged from 8 to 28% (Table 3).
Greatest primisulfuron absorption occurred with the use of POA plus UAN. At 1 and 6
hours after application, absorption was 21 and 28%, respectively, with POA plus UAN.
Absorption with M80 and N15 plus UAN was 22% and 20%, respectively, 6 hours after
application. Herbicide absorption was similar when either NIS or POA was used.

Foliar absorption of nicosulfuron and primisulfuron improved from the addition of
UAN to either NIS or POA as compared to either component applied alone at both 1 and
6 hour harvest intervals. Similar results were reported for thifensulfuron and chlorimuron
combined with NIS plus UAN or NIS alone in velvetleaf (3, 9, 10).

Foliar absorption of nicosulfuron was similar when POA was applied with or without
atrazine (Table 2). Absorption of primisulfuron was greater 6 hours after application with
atrazine plus POA than when POA was the only adjuvant (Table 3). Previous research has
indicated possible reductions in nicosulfuron or primisulfuron efficacy when tank-mixed with
atrazine (8, 11, 12, 21). Based on our observations in quackgrass, antagonism with

nicosulfuron or primisulfuron combinations with atrazine was not due to reduced

55

.8838 85:» 28> macaw-.3809.
80880.: 88.8 99% cm 383??
Ave-.88 o: 38 6.. as, .2352: - 3.8“ o: .59: _. 2: a 8.28.8 8.53..
.2888 u MH< do noon veg—>508 u
022 REE-.8 2:0: 28:: 83588988 sown u Z<D .855?“ no 8:20.509 u <Om 88%-tam 083:0: u 22 ”$5883

 

 

 

 

 

: a. mu m m «”553
£- 8 qfi E c 3 + as. w 8: <08 + a:
3 -- ha 8 a 8 om:
a 3 2 mm a c... + 3 2.3 + <8
5 3 n: 8 a 3. + 2 55 + a2
8 - a.“ 2 w 3. ES
8 a S: a a 3 <8
3 a mm m : S . £2
E 8 nm : a -- 2oz
. as: a m as 8.88.5.5
s as ....... as ------.- >\> as
83 33 “8088? 8:2. c .50; g 08% .3:a>=.€<
9.9.88 mambo—ogc $3th sou—89.. U: ammo-m

 

.3895?“ 82.38
.38» 3 380mm 3 80893888 .8 .6850 Row 28 030808» on. 8 883—83 .3 883388890: .«0 coma-535 ammo-m .m. See-u

56

nicosulfuron or primisulfuron foliar absorption.

Measurements of spray droplet diameter on the leaf surface at dryness were taken

prior to harvest. The least amount of spread was observed in treatments containing either
no adjuvant or UAN. All other adjuvants sufficiently modified droplet surface properties
to increase droplet diameters (Tables 2, 3). Comparisons of droplet diameter to herbicide
absorption appear unrelated since adjuvants with similar absorption had large differences
in droplet diameter. Based on this observation, the degree of droplet dispersal on a leaf is
not a good indicator of the potential for an adjuvant to modify herbicide absorption. Similar
findings were reported by Wanamarta et. a1 (25) for sethoxydim (2-[1-(ethoxyimino)butyl]-5-
[2-ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one) use on quackgrass.
Herbicide efi‘icacy. Control of three-leaf quackgrass with nicosulfuron and primisulfuron in
the greenhouse was dependant upon adjuvant selection. The addition of UAN to POA
significantly increased quackgrass control with nicosulfuron (35 g ha") from 76% to 89% 30
days after treatment (Table 1). Similar results were observed with primisulfuron. Since
nicosulfuron and primisulfuron absorption was greater with POA plus UAN than POA
alone, differences in control appear related to foliar herbicide absorption. Similar results
have been reported with thifensulfuron and chlorimuron absorption and control of velvetleaf
(3, 9, 10).

Similar growing seasons were observed in field studies in 1989 and 1990. In both
seasons, rainfall was adequate to above normal with normal temperatures. In general,
quackgrass control in 1989 was greater and more consistent than that observed in 1990
(Tables 2, 3). Quackgrass emergence from the soil and shoot height at the time of
postemergence application was more uniform in 1989 than in 1990. Uniformity differences
can be attributed to differences in primary tillage depth and resulting quackgrass rhizome

distribution. The moldboard plow depth was greater in 1990 than in 1989, probably resulting

57

in greater vertical rhizome distribution through the plow layer in 1990. As a result,
quackgrass shoot emergence occurred over a greater time interval. This lead to a wide
range of quackgrass heights at the time of application in 1990 and more shoot emergence
after application than in 1989. This would account for greater variability observed in 1990
quackgrass control results.

Quackgrass control within treatments was similar throughout the growing season
(Tables 2, 3). Early season control ratings are presented since control was similar
throughout the growing season. All herbicide treatments experienced some degree of new
shoot emergence after treatment. Typically new shoots were not observed until 60 days
after treatment, however, new shoots were observed as early as 30 days after treatment in
1990.

Postemergence applications of nicosulfuron (35 g ha") without an adjuvant provided
88% and 80% quackgrass control 30 days after treatment in 1989 and 1990, respectively
(Table 2). In 1989, the use of NIS, POA, NIS plus UAN, and POA plus UAN with
nicosulfuron significantly increased control compared to no adjuvant. Nicosulfuron applied
with NIS, POA or POA plus UAN gave similar quackgrass control (294%). In 1990, no
significant differences in control were observed 30 days after treatment regardless of the
adjuvant used. The lack of differences were due in part to the emergence of new quackgrass
shoots following the postemergence herbicide application (data not presented). Examination
of these late emerging shoots indicated that they originated form greater soil depths than
nearby treated shoots which had emerged prior to herbicide application.

Quackgrass control with primisulfuron was at least 90% in 1989 (Table 3).
Compared to primisulfuron alone, the addition of NIS, NIS plus UAN, POA plus UAN, and
atrazine plus POA significantly increased quackgrass control. In 1990, none of the adjuvants

applied with primisulfuron provided greater control than primisulfuron applied alone.

 

58
The addition of UAN to either NIS or POA did not increase nicosulfuron (Table 2)

activity on quackgrass compared to NIS or POA without UAN. Similar results were
observed with primisulfuron in both years (Table 3). Greenhouse studies with both
herbicides revealed greater foliar absorption and activity from the addition of UAN to either
POA or NIS. These conflicting results may be due to differences in quackgrass epicuticular
wax composition due to the different environments in which the plants were grown.

The addition of atrazine to nicosulfuron plus POA reduced quackgrass control from
94% to 89% in 1989 but not in 1990 (Table 2). Primisulfuron efficacy was not affected by
atrazine in 1989 (Table 3). However, in 1990, primisulfuron plus POA efficacy declined
from 91% to 76% when atrazine was added to the treatment solution. Foliar absorption
studies indicated that atrazine did not affect the absorption of 1‘C-nicosulfuron or 1‘C—
primisulfuron in quackgrass (Tables 2, 3). Hart and Penner (12) observed reduced control
of giant foxtail and velvetleaf when primisulfuron was applied with atrazine. They reported
no effect on primisulfuron absorption; however, primisulfuron translocation to meristematic

regions declined in the presence of atrazine. A similar response may occur in quackgrass.

ACKNOWLEDGMENTS
The authors wish to thank CIBA-GEIGY and 8.1. DuPont for supplying the 1‘0
labeled primisulfuron and “C-labeled nicosulfuron, respectively. The generous financial
support of this research by El. DuPont is also greatly appreciated. Our sincere gratitude

is extended to Christy Sprague for her technical assistance in this research.

 

10.

11.

12.

13.

14.

15.

LITERATURE CITED

Anonymous. 1990. Accent herbicide specimen label. E.I. Du Pont de Nemours and
Company, Agricultural Products, Wilmington, DE 19898.

Anonymous. 1990. Beacon herbicide product label. CIBA-GEIGY Corporation,
Agricultural Division, Greensboro, NC 27419.

Beckett, T. H. and E. W. Stoller. 1991. Effects of methylammonium and urea
ammonium nitrate uptake of thifensulfuron in velvetleaf (Abutilon theophrasti).
Weed Sci. 39:333-338.

Bhowmik, P. C., B. M. O’Toole, and J. Andaloro. 1992. Effects of nicosulfuron on
quackgrass (Ebm'gzh repens) control in corn (Zea mays). Weed Technol. 6:52-56.

Bruce, J. A and J. J. Kells. 1988. Quackgrass (Agropyron repens (L.) Beauv.) control
in corn with selective postemergence herbicides. Proc. North Cent. Weed Cont.
Conf. 43:33.

Bruce, J. A. and J. J. Kells. 1990. Postemergence quackgrass control in corn. Proc.
North Cent. Weed Sci. Soc. 45:31.

Camacho, R. F. and L. J. Moshier. 1991. Absorption, translocation, and activity of
CGA-136872, DPX-V9360, and glyphosate in rhizome johnsongrass (Sorghum
halepense). Weed Sci. 39:354-357.

Carey, J. B., P. B. Knoerr, and J. J. Kells. 1992. Herbicide interactions with
nicosulfuron and primisulfuron in corn. Abstr. Weed Sci. Soc. Am. 32:12.

Fielding, R. J. and E. W. Stoller. 1990. Effects of additives on the efficacy, uptake
and translocation of the methyl ester of thifensulfuron. Weed Sci. 38:172-178.

Fielding, R. J. and E. W. Stoller. 1990. Effects of additives on efficacy, uptake, and
translocation of chlorimuron ethyl ester. Weed Technol. 41264-271.

Hart, S. E., J. J. Kells, and D. Penner. Influence of adjuvants on the efficacy,
absorption, and spray retention of primisulfuron. Weed Technol. In review.

Hart, S. E., and D. Penner. Physiological basis for the antagonistic effect of atrazine
on the efficacy of primisulfuron to giant foxtail (Setaria faben') and velvetleaf
(Abutilon theophrasti). Weed Sci. in review.

Kells, J. J. and P. B. Knoerr. 1990. Tank-mix herbicide combinations for corn with
nicosulfuron and primisulfuron. Proc North Cent. Weed Sci. Soc. 45:17.

Manthey, F. A. and R. Matysiak. 1990. Oils and emulsifiers affect imazethapyr
phytotoxicity. Proc. North Cent. Weed Sci. Soc. 45:14-15.

Mitich, L W. 1987. The Devil’s grass: quackgrass. Weed Technol. 1:184-185.

59

 

16.

17.

18.

19.

20.

21.

22.

23.

24.

26.

27.

6O

Morton, C. A. and R. G. Harvey. 1989. DPX-V9360 for weed control in field and
sweet corn. Abstr. Weed Sci. Soc. Am. 29:2.

Morton, C. A. and R. G. Harvey. 1990. DPX—V936O for control of giant foxtail
(Setaria faberi Herrm.) in field corn. Abstr. Weed Sci. Soc. Am. 30:4.

Moses, A. J ., C. L. Kern, T. B. Threewitt, D. E. Stamm, T. D. Taylor, M. D.
Johnson, J. Cantwell, T. R. Dill, and G. R. Gillespie. 1989. Summary of the 1989
CGA-136872 EUP program. Proc. North Cent. Weed Sci. Soc. 44:36.

Nalewaja, J. D., Z. Woznica, and F. A. Manthey. 1991. DPX-V9360 efficacy with
adjuvants and environment. Weed Technol. 5:92-96.

Penner, D. 1989. The impact of adjuvants on herbicide antagonism. Weed
Technol. 3:227-231.

Radliff, E. E. and G. Kapusta. 1990. Grass control in corn as influenced by
antagonistic interactions between DPX-V936O and selected postemergence
herbicides. Proc. North Cent. Weed Sci. Soc. 45:28.

Reinhart, M. W., M. J. Dobrotka, and S. W. Rowe. 1989. DPX-V9360, performance
on difficult to control grass species in corn. Proc. North Cent. Weed Sci. Soc. 44:30.

Roggenbuck, F. C., L. Rowe, D. Penner, L. Petroff, and R. Burow. 1990. Increasing
postemergence herbicide efficacy and rainfastness with silicone adjuvants. Weed
Tech. 4:576-580.

Ruiter, H. de, A.J.M. Uff‘mg, E. Meinen, and A. Prins. 1990. Influence of
surfactants and plant species on leaf retention of spray solutions. Weed Sci. 38:567-
572.

Wanamarta, G., D. Penner, and J. J. Kells. 1989. Identification of efficacious
adjuvants for sethoxydim and bentazon. Weed Technol. 3:60-66.

Wyse, D. L. 1976. Quackgrass control in field crops. Proc. North Central Weed
Cont. Conf. 31:152-154.

Yenish, J. P. and J. D. Doll. 1990. Efficacy of CGA-136872, DPX-V9360, and DPX-
79406 on quackgrass (Agropyron repens (L.) Beauv.) control in corn. Abstr. Weed
Sci. Soc. Am. 30:5.

CHAPTER 4

EFFECT OF GROWTH STAGE AND ENVIRONMENT ON FOLIAR ABSORPTION,
TRANSLOCATION, AND ACTIVITY OF NICOSULFURON IN

QUACKGRASS mm ms (L.) Nevski]

ABSTRACT

Experiments were conducted to examine the influence of adjuvant, grth stage, air
temperature, and soil moisture on nicosulfuron activity, absorption, and distribution in
quackgrass. The addition of 28% urea-ammonium nitrate liquid fertilizer (UAN) to 1‘C-
nicosulfuron plus petroleum oil adjuvant (POA) provided greater 1‘C absorption than POA
alone. Translocation of 1“C with POA alone at 168 h after treatment (HAT) was similar to
POA plus UAN at 24 HAT.- Total translocation was similar at 168 HAT, regardless of
adjuvant. Foliar absorption of 1"C-nicosulfuron by quackgrass was greater in one-leaf than-
five-leaf plants. Total translocation of 1‘C-nicosulfuron was similar regardless of growth
stage. However, nicosulfuron was more phytotoxic to three- and five-leaf than one-leaf
quackgrass. 1“C-Nicosulfuron absorption, translocation, and accumulation increased with
increasing temperatures independent of soil moisture. Under adequate soil moisture
conditions (-0.03 MPa) nicosulfuron activity was not influenced by temperature.
Nicosulfuron efficacy was not influenced by soil moisture at a cool (11/6 C) temperature.
As plant moisture stress increased, due to low soil moisture and increasing air temperature,
nicosulfuron efficacy declined. Differences in nicosulfuron efficacy due to growth stage or
environmental conditions could not be explained by differential l“C recovery, absorption,

translocation, or accumulation. Nomenclature: Nicosulfuron, 2-[[[[(4,6-dimethoxy-2-

61

62
pyrimidinyl)amino]carbonyl]amino]sulfonyl]-N,N-dimethyl-3~pyridinecarboxamide;
quackgrass, Eb’trigia repens (L.) Nevski #1 AGRRE.

Additional index words. AGRRE, application timing, control, DPX—V9360, moisture stress,

soil moisture, temperature, urea-ammonium nitrate.

Introduction

Nicosulfuron is a postemergence herbicide which provides selective grass and
broadleaf weed control in corn (1). This sulfonylurea herbicide inhibits acetolactate
synthase (ALS)2 to effectively block synthesis of the branched-chain amino acids valine,
leucine, and isoleucine (1). Previous research concluded that herbicide phytotoxicity
resulted from amino acid starvation, however, researchers now believe that accumulation
of the toxic metabolite, a-amino butyric acid is responsible for the phytotoxicity induced by
an ALS inhibitor (12, 17).

In field studies, nicosulfuron has provided effective control of quackgrass. Shoot
regrowth from vegetative reproductive tissues has been observed in some instances (Chapter
2). Quackgrass control was enhanced by the addition of 28% urea-ammonium nitrate liquid
fertilizer (UAN)‘ to nicosulfuron plus petroleum oil adjuvant (POA)‘. Nicosulfuron
absorption was greater in the presence of POA plus UAN than with UAN alone. Total
recovery of 1“C was lower with POA plus UAN treatments, possibly due to greater
translocation from the treated leaf (Chapter 2).

Control of quackgrass and johnsongrass [Sorghum halepense (L.) Pers.] with

 

1Letters following this symbol are a WSSA-approved computer code from Composite
List of Weeds. Revised 1989. Available from WSSA, 309 West Clark Street, Champaign,
IL 61820.

2Abbreviations: ALS, acetolactate synthase; UAN, 28% urea-ammonium nitrate liquid
fertilizer; POA, petroleum oil adjuvant; HAT, hours after treatment.

63

nicosulfuron is influenced by grth stage. Phytotoxicity improved when nicosulfuron was
applied to larger quackgrass (Chapter 2) and johnsongrass (4, 15) rather than smaller plants.
Control differences could not be attributed to differential absorption, translocation, or
accumulation of nicosulfuron in johnsongrass (15).

Soil moisture content and air temperature has previously influenced sulfonylurea
efficacy. Oyaizabal and Owen (16) observed greatest nicosulfuron activity on well watered
woolly cupgrass [Eriochloa villosa (Thunb.) Kunth] and shattercane [Sorghum bicolor (L.)
Moench]. Kochia [Kochia scoparia (L.) Schrad.] control with thifensulfuron (3-[[[[(4-
methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]amino]sulfonyl]-2-thiophenecarboxylic
acid) (13) and chlorsulfuron (2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-
yl)amino]carbonyl]benzenesulfonamide) (14) was also better at field capacity than when
plants were drought stressed. However, velvetleaf (Abutilon theophrasti Medicus) control
was similar with thifensulfuron regardless of soil moisture (20). Greater herbicide efficacy
was observed with lower air temperatures with chlorsulfuron (l4), chlorimuron (2-[[[[(4-
chloro-6-methoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]benzoic acid) (7), and
thifensulfuron (20). However, Nalewaja and Adamczewski (13) reported greater kochia
control with thifensulfuron when day/ night temperatures were increased from 10/ 8 to 30/24
C. Quackgrass growth is generally suppressed by increasing temperatures (10) which may
adversely influence nicosulfuron phytotoxicity.

Quackgrass research was initiated to examine: a) the effect of UAN on the
absorption and distribution of nicosulfuron, b) the influence of growth stage on nicosulfuron
absorption, distribution, and activity, and c) soil moisture and air temperature effects on

nicosulfuron absorption, distribution, and activity in quackgrass.

 

Materials and Methods
General experimental procedures. Greenhouse experiments were conducted to examine
foliar absorption and translocation of l‘C-nicosulfuron over time as affected by UAN.
Treatments were arranged as a factorial with two herbicide treatments and three harvest
timings; 24, 72, and 168 h after application (HAT)‘. Plants were treated with a foliar
application of nicosulfuron (35 g ha") plus petroleum oil adjuvant (POA)‘ with and without
UAN.

Greenhouse conditions were maintained at 25 C i 4 C with a 16-h photoperiod of
natural and supplemental metal halide lighting with a midday photosynthetic photon flux
density of 1000 uE m‘2 s". A rhizome from a slightly pubescent quackgrass biotype was
selected from a field in Williamston, MI. This biotype served as a propagation source for
all plants to maintain genetic uniformity within studies. Quackgrass plants were raised from
single unbranched three-node rhizome segment placed at a 2-cm depth in l-L plastic pots
containing potting medium’. Plants were watered as needed and fertilized weekly with 50-
ml of water soluble fertilizer solution (400 ppm N, 400 ppm P205, 400 ppm K20). Aphid
infestations were controlled with foliar applications of acephate (O,S-dimethyl
acetylphosphoramidothioate).

Radiolabeled herbicide solutions were prepared in the laboratory, utilizing 2-
pyrimidine 1"C-nicosulfuron with a specific activity of 2.3 MBq mg" and 98.8% purity as
determined by high-performance liquid chromatography. Labeled nicosulfuron was dissolved
in tetrahydrofuran and then utilized to prepare a 390 Bq pl" treatment solution.

Tetrahydrofuran was then evaporated in a nitrogen stream and replaced with deionized

water. The labeled herbicide solution was supplemented with deionized water, formulated

 

3Baccto Professional Planting Mix. Michigan Peat Company, P O Box 980129, Houston,
TX 77098. '

64

65'

nicosulfuron product‘ and formulation blank. Two separate treatment solutions were
prepared to include POA’ at 1% v/v and POA plus UAN at 4% v/v. Final treatment
concentrations were 415 umol nicosulfuron plus 57 mg L" formulation blank. These
concentrations correspond to a broadcast application of nicosulfuron at 35 g ha'1 delivered
in 206 L water ha".
Effect of UAN. Quackgrass plants selected for treatment had two culms each originating
from adjacent buds on the parent rhizome. One of these culms had three fully developed
leaves while the other culm had not yet developed a true leaf. These three-leaf plants
ranged from 20 to 33 cm averaging 25-cm in height. These plants represent the typical
quackgrass size and stage observed at the time of field nicosulfuron applications. Prior to
herbicide application, the uppermost fully developed leaf (third leaf) was covered with
plastic wrap. The plants then received a broadcast foliar application of nicosulfuron (35 g
ai ha") plus either POA (1% v/v) or POA plus UAN (1% plus 4% v/v). This application
was made with a continuous link-belt single nozzle sprayer equipped with a 8001E‘ tip
calibrated to deliver 206 L ha". Upon drying, the plastic wrap was removed from the third
leaf to allow for application of l‘C-nicosulfuron. A total of 5480 Bq were delivered from a
microsyringe to the third leaf as seven 2-ul droplets of treatment solution.

Plants were harvested at 24, 72, and 168 h after herbicide treatment. At harvest
time, the treated leaf was excised and rinsed for 45 s in a scintillation vial containing 3 ml

methanol to remove unabsorbed l“C. Leaf washes conducted immediately after l‘C

 

‘Accent 75 WDG herbicide. E. I. duPont deNemours and Co., Wilmington, DE 19898.

5Herbimax, 83% petroleum oil, 17% adjuvant, a product of Loveland Industries, Inc. PO
Box 1289, Greeley, CO 80632.

‘Teejet flat fan tips. Spraying Systems Co., North Avenue and Schmale Road, Wheaton
IL 60188.

66

application effectively removed at least 98% of the unabsorbed 1‘C. Plants were uprooted
and gently washed in water to remove soil from the roots. Plants were then sectioned into
the following seven parts: treated leaf, above treated leaf, below treated leaf (to soil
surface), crown, parent rhizome and associated roots, new culms, and new rhizomes. Since
few plants had new rhizomes, the data for these parts were pooled with the new culms. All
plant parts were frozen and later lyophilized. Dry weights of each part were recorded prior
to combustion in a biological sample oxidizer. A mixture of carbon dioxide absorbent and
scintillation fluid (1:2 ratio) was used to trap evolved l‘COzz. Each methanol leaf wash vial
received 15-ml scintillation fluid. All samples were then quantified by liquid scintillation
spectrometry correcting for quench.
Effect of growth stage. Experiments were conducted to examine the effect of growth stage
on nicosulfuron activity, absorption, and distribution in quackgrass. Quackgrass plants were
established in the greenhouse as previously described. Plantings were delayed in order to
simultaneously obtain plants at one-, three-, and five-leaf growth stages. Quackgrass plant
heights averaged 14, 24, and 32-cm for one-, three-, and five-leaf plants, respectively, at the
time of herbicide application. At this time, separate control and 1“C translocation studies
were initiated. To examine quackgrass control, nicosulfuron was applied at 0, 8, 16, and 32
g ha’1 with POA at 1% v/v to one-, three-, and five-leaf quackgrass. Treatments were
applied to plants as previously described. Quackgrass control was visually evaluated 30 days
after treatment.

Radiolabeled nicosulfuron solution was prepared as previously described to contain
POA at 1% v/v. The uppermost fully developed quackgrass leaf was covered with plastic
wrap. Nicosulfuron (35 g ha") plus POA (1% v/v) was applied to the plants as previously
described. After removal of the plastic wrap, the leaf was treated with l"C-nicosulfuron

solution as previously described. Plants were harvested at 168 HAT and 1‘C quantified.

67

Plants were sectioned as previously described except that tillers from the treated culm were
treated as an additional section.

Effect of air temperature and soil moisture. Studies were initiated to examine the effect
of air temperature and soil moisture on nicosulfuron activity, absorption, and distribution
in quackgrass. Treatments were arranged-as a factorial with two soil water potentials, -0.03
and -0.2 MPa, and three day/night air temperatures of 11/6, 21 /16, and 31/26 C.

Plants were initiated in the greenhouse at 26 i 3 C with a 16-h photoperiod of
natural and supplemental high-pressure sodium lighting with a midday photosynthetic
photon flux density of 1000 pE m“2 s". Three node rhizome segments were planted in 0.5-L
pots containing sandy clay loam soil (54% sand, 26% silt, 20% clay) with 2.3% organic
matter and pH of 6.7. Plants were maintained as previously described.

Through previous research, a moisture retention curve was developed for this
particular soil". From this curve, the soil water content (g/ g) could be determined for a
specific soil water potential (MPa). At planting, the initial soil moisture content was
determined for the soil. This moisture level and the amount of soil (g) in each pot was
utilized to establish a specific soil water potential for each pot.

Three days prior to herbicide application, quackgrass plants were selected for
uniformity and transferred into growth chambers with day/ night temperatures of 11/6,
21/16, and 31/26 C. Chambers were maintained at 60% relative humidity with a 16-h
photoperiod from fluorescent and incandescent lighting with a photosynthetic photon flux
density of 750 [E m”2 s-l. Each growth chamber contained two groups of plants, well-
watered and water-stressed. Plants were watered twice daily to 18 and 9.5% (wt/wt) soil

moisture which correspond to water potentials of -0.03 and -0.2 MPa, respectively. These

 

7Zollinger, Richard K. 1989. Perennial sowthistle (Sonchus arvensis L.) distribution,
biology and control in Michigan. Ph. D. Dissertation, Michigan State University.

68

values were established from the soil moisture curve described above.

Separate studies were initiated to examine nicosulfuron activity and 1‘C distribution.
Quackgrass plants for the efficacy study were removed from the growth chamber and treated
with nicosulfuron at rates of 0, 8, 16, and 32 g ha'l plus POA (1% v/v) as previously
described and then returned to the grth chamber once leaves were dry. Seven days after
treatment, all plants were returned to the greenhouse and watered as needed. Thirty days
after treatment, all plants were visually evaluated for control.

Plants utilized in the l‘C-nicosulfuron absorption and translocation study were pre-
sprayed and then treated with l‘C—nicosulfuron plus POA as previously described. At the
time of application, all plants had three fully developed leaves and averaged 18-cm in height.
Within 60 minutes after treatments, plants were returned to the growth chambers and
maintained until harvest 168 h later. New culms and new rhizomes were not consistently
present on all plants. As a result, 1‘C accumulation in these parts are not presented, but
their contribution to MC recovery and translocation is included.

Data analysis. Treatments in all studies were arranged as a factorial in a randomized
complete block design with four replications repeated over time. All data were subjected
to analysis of variance. Significant repeat main effects were observed in some translocation
studies, but no repeat by factor interactions were observed. As a result, treatment means
presented are the result of the combined analysis. Treatment mean separations were made
utilizing Fisher’s protected least significant difference at the 5% confidence level. Data
representing distribution of nicosulfuron were expressed as a percentage of total

radioactivity applied to the plant.

 

Results and Discussion

Effect of UAN. Recovery of 1“C from quackgrass 168 HAT was at least 80% of that applied
(Table 1). Recovery decreased as harvest was delayed. The addition of UAN to
nicosulfuron plus POA generally resulted in less 1‘C recovery compared to nicosulfuron plus
POA alone. These losses may be attributed to root exudation of 1“C (5), metabolism and
subsequent release of carbon dioxide (6), or loss of 1‘C containing roots during plant harvest.
Reduced recovery at 168 HAT is presumed to be attributed to a combination of these
factors, but research was not conducted to identify the source of these losses. Camacho et
al. (3) obtained 88% recovery of applied 1‘C—nicosulfuron in johnsongrass at 24 HAT.

Foliar absorption of l‘C-nicosulfuron when applied with POA increased from 18%
to 42% as harvests were delayed from 24 to 168 HAT (Figure 1). These results are contrary
to those obtained in Chapter 3 where l‘C-nicosulfuron plus POA absorption reached a
plateau within the first four hours of a 24 h study. These differences between studies may
be due to differences in leaf cuticular wax composition or environmental conditions at the
time of application. In addition, the rate of increase in absorption may have been so slow
that the increase was not obvious in the 24 h experiment in Chapter 3.

The addition of UAN to 1‘C-nicosulfuron plus POA provided significantly greater
l"C absorption at all harvest times than without UAN. These results concur with those
found in Chapter 3 where the addition of 28% UAN to POA increased nicosulfuron
absorption in quackgrass. The addition of UAN to nonionic surfactant has also improved
thifensulfuron and chlorimuron absorption in velvetleaf (2, 8, 9). Similar absorption of 1‘C-
nicosulfuron was observed with the adjuvants POA plus UAN regardless of harvest time.

Radioactivity in the treated leaf increased from 15 to 30% of applied from 24 to 168

HAT, respectively with POA (Figure 2). With POA plus UAN, 41% of the applied 1‘C was

69

70

Table I. 1‘C recovered from quackgrass at 24, 72, and 168 h after application of “C-
nicosulfuron as affected by UAN.

 

1"C Recovery after application

 

 

 

 

Adjuvant‘ 24 72 168 h
% of applied

POA 94 92 87

POA + UAN 88 90 80

LSD-,5" ' 5

 

 

'Treatment include petroleum oil adjuvant (POA) at 1% v/v with and without 28% urea-
ammonium nitrate liquid fertilizer (UAN) at 4% v/v.
bMean comparisons valid within or between columns.

 

71'

100

 

80—

 

‘4C absorption (70 of applied)

‘ ’ k-A POA + UAN
e—e POA

 

 

 

O l l l l l T T

O 24 72 120 168

Time after treatment (h)

Figure 1. Foliar absorption of 14C-nicosulfuron in quackgrass as affected by UAN.
Treatments included petroleum oil adjuvant (POA) at 1% v/v with and
without 28% urea-ammonium nitrate liquid fertilizer (UAN) at 4% v/v.

 

72

100

 

80—

(70 of applied)

07

O

l

5)
b0

n

()1

 

14C accumulation in treated leaf

2 ’ k-A POA + UAN
o—o POA

 

 

 

 

O l l l l l l l

O 24 72 120 168

Time after treatment (h)

Figure 2. Accumulation of 1"C in the treated leaf of quackgrass as affected by UAN.
Treatments included 1“C-nicosulfuron plus petroleum oil adjuvant (POA) at
1% v/v with and without 28% urea-ammonium nitrate liquid fertilizer

(UAN) at 4% v/v.

73

recovered from the treated leaf at 24 HAT. Similar 1‘C accumulation was observed at 168
HAT. Accumulation of 1‘C in the treated leaf was greater with POA plus UAN than with
POA alone at all harvest times.

Translocation of 1‘C from the treated leaf during the first 24 HAT progressed more
rapidly when the treatment included POA plus UAN compared with POA alone (Figure 3).
For treatment with POA alone, 168 HAT were needed to obtain 1‘C translocation equivalent
to that obtained with POA plus UAN at 24 HAT. The accumulation of “C in the treated
leaf and translocation from the treated leaf followed a similar pattern (Figures 2 and 3).
This suggests that the amount of 1‘C translocated from the treated leaf increased as a result
of increased l4C concentrations in the treated leaf.

The amount of radioactivity translocated from the treated leaf accounted for less
than 15% of that applied (Table 2). Of the total 1‘C translocated, at least 85% moved to
plant parts below the treated leaf and 29% accumulated in below-ground parts and
developing shoots. The proportion and direction of 1‘C translocated indicate that
nicosulfuron is phloem mobile in quackgrass. Similar accumulation patterns were observed
with nicosulfuron in johnsongrass (3, 15). These studies also reported greater accumulation
of 1‘C in shoot tissue immediately below the treated leaf than in rhizome tissues. Less than
2.5% of the applied 1‘C accumulated in the crown or parent rhizomes of quackgrass. In
johnsongrass, less than 5% of the absorbed 1“C was translocated to rhizome tissues (3, 15).
Accumulation of 1‘C in plant parts generally increased over time when POA was used as the
adjuvant, but this was not observed with POA plus UAN. These trends were not as evident
with 1‘C concentration. This may be due to the increased variability associated with this
type of concentration measurement. The use of POA plus UAN with nicosulfuron provided
greater absorption and more rapid translocation than POA alone. Greater nicosulfuron

phytotoxicity was observed in Chapter 3 with POA plus UAN than with POA alone. This

74

 

   
 

 

 

 

50
A
U .
.9
E
Q 40—
O l
B
N" 30—
V
C u
.9
8 20— LSDDS — 3
O
Tn ‘ ,,,,,, A
C __________
g lO~ ——————
g) ‘ r—x POA + UAN
'- o—o POA
O l l T l
O 24 72 120 168

Time after treatment (h)

Figure 3. Translocation of 1‘C from the treated leaf of quackgrass as affected by UAN.
Treatments included 1‘C—nicosulfuron plus petroleum oil adjuvant (POA) at
1% v/v with and without 28% urea-ammonium nitrate liquid fertilizer
(UAN) at 4% v/v.

 

75

.958 85? 38> macaw-.388 .822.

.35 as a 923 38:»... 28: 28:.
838888-38 «awn 8253 8.8 as? A>\>v ex: 8 A<Omv 898:8 :0 8:03.32. .88 coda—388.0: eds—o8 888.8 80882.?

 

 

 

 

mZ Nun Sm mmm m2 @— m; fig 800.? 302
m2 Nn em on mZ Ya —.~ VA 083:1 808m
m2 mam 5mm vow mz dd md bd 8580
m2 N3. awn Eb mZ fin in Wm .80— voaaob 320m
mZ hem wmm m2 ed Nd m4 dd .82 ©0805 o>on< Z<D + <Om
mZ ww— we 8 m2 ad ad vd 809? 302
3 av an 3 rd o4 _.H md 080N3— 808m
mz vow 3 v «.2 _d bd m d Nd 839.0
dvm don 3N Na 5N dd ON NA .82 880.: 320m
m2 59 ca R. pd w; wd Nd .80— uouuoh o>on< <Om
ii... _.w8 8nd tit... i... dodge 8 88 t-..-
sadfl __ me" «e «N .8qu a 88 Q. an Ex. 82m 895%....
83.888ch 8=OE< _

 

.«8— Bus-5 0.: 89¢ gag—mam: 03 HO Gomuw—QE:8<

 

838388 ~28 : mg 28 .Q. .vu 8 82 $080.: 2: 80¢ 388—88“ 0: .8 8888833» N 885
we

76

difference may be explained by greater nicosulfuron absorption and more rapid translocation
with POA plus UAN than with POA alone.

Effect of growth stage. Absorption and translocation of 1‘C-nicosulfuron plus POA was
examined in one-, three-, and five-leaf quackgrass to explain differences in quackgrass
control Total recovery of 1‘C was greater from three- and five-leaf quackgrass than one-leaf
plants at 168 HAT (Table 3). These results are possibly due to differences in 1‘C lost during
soil removal from plant roots. The 1‘C concentration was greater in one-leaf plant roots
than either three- or five-leaf plants (data not presented). This concentration difference
would result in greater l4C losses for one-leaf than three- or five-leaf plants assuming similar
quantities of roots were lost during the harvesting process.

The amount of “C absorbed and remaining in the treated leaf was greater in one-
leaf than in five-leaf quackgrass plants (Table 3). Despite the differences in absorption, the
amount of 14C translocated from the treated leaf was similar among all growth stages.

The crown and parent rhizome of one-leaf plants accumulated more 1‘C than three-
or five-leaf plants (Table 4). Translocation of 14C to other plant parts was similar regardless
of plant growth stage.

Quackgrass control with nicosulfuron was greater when plants were treated at the
three- or five-leaf stage than at the one-leaf stage (Table 5). This effect was observed with
application rates of 16 and 32 g ha‘1 applied with POA alone. In previous field research,
four-leaf quackgrass plants were controlled more effectively with nicosulfuron than two-leaf
plants (Chapter 2). Other researchers have reported that nicosulfuron efficacy was greater
when applied to larger johnsongrass (>five-leaf) rather than smaller plants (4, 15, 19).

Since nicosulfuron absorption and accumulation in vegetative reproductive tissues
was greater in one-leaf quackgrass than three- or five-leaf quackgrass, control of one-leaf

quackgrass might be expected to be greater than three- or five-leaf quackgrass. However,

77‘

Table 3. The effect of quackgrass grth stage on 1‘C recovery, absorption, and
distribution in quackgrass 168 h after l‘C-nicosulfuron application'.

 

1"C recovered

 

 

 

 

1-leaf 3-leaf S-leaf LSDm"
% of applied
Total recovery 84 89 90 4
Absorption 34 32 27
Treated leaf 26 22 17 6
Translocatedc 8 10 10 NS

 

”Treatments included petroleum oil adjuvant at 1% v/v.
bMean comparisons valid within rows.
“Translocated from the treated leaf.

78

Table 4. Accumulation of 1‘C in quackgrass plant parts 168 h after application of “C-
nicosulfuron as affected by growth stage“.

 

Accumulation of 1‘C translocated from
the treated leaf

 

 

Plant part 1-leaf 3-leaf 5-leaf LSDm"
-- ------- % of applied -- -----------
Above treated leaf 1.2 1.3 0.9 NS
Below treated leaf 3.5 6.2 7.0 NS
Tillers -- 1.1 0.5 NS
Crown 1.7 0.5 0.1 0.6
Parent rhizome 1.0 0.6 0.4 0.4
New shoots 0.3 0.2 0.2 NS
New rhizomes -- 0.3 0.9 NS

 

'All treatments included petroleum oil adjuvant at 1% v/v.
t’Mean comparisons valid within rows.

79

Table 5. Quackgrass control in the greenhouse with nicosulfuron as affected by

quackgrass growth stage.

 

Quackgrass control”

 

 

 

Nicosulfuron
rate‘ l-leaf 3-leaf 5-leaf
g ai ha'1 %
0 0 0 0
8 2 10 10
16 10 41 50
32 51 73 83
LSD.”c 14

 

 

 

‘All treatments included petroleum oil adjuvant at 1% v/v.
l’Evaluated visually 30 days after treatment

cMean comparisons valid within and between columns.

80

the opposite control results were observed in greenhouse efficacy trials and field
experiments (Chapter 2).

Obrigawitch et al. (15) and Camacho et al. (3) observed greater control of
johnsongrass with nicosulfuron as plant size increased to 8 leaves. Control differences could
not be attributed to differences in translocation, accumulation, or foliar absorption (3, 15).
Obrigawitch et al. (15) reasoned that rhizome carbohydrate reserves were at a minimum in
the larger growth stages which made plants more susceptible to nicosulfuron applications
at this time. This may not be the true for quackgrass. In their review of quackgrass, Holm
et al. (10) reported minimum carbohydrate reserves in rhizomes when plants were showing
two developed leaves. At this stage, plants are most susceptible to environmental stress or
disturbance by man. In our greenhouse and field research, plants with more than two leaves
were controlled more effectively with nicosulfuron than plants with two leaves or less.

It is likely that the effect of growth stage on quackgrass control with nicosulfuron is
due to differences in spray retention. Since one-leaf plants have less leaf area than three-
or five-leaf plants, less spray solution will be intercepted by the one-leaf plants. This
reduction in amount of herbicide available for absorption may be responsible for less
complete control of one-leaf plants compared to three- or five-leaf plants.
Effect of air temperature and soil moisture. Quackgrass plants exposed to a day/night
temperature of 21 /16 C with -0.2 MPa soil water potential and 31 /26 C with 0.03 and 0.2
MPa were visibly stressed. Symptoms included rolled leaves, growth cessation, and purple
discoloration of plant tissue. Approximately three days after treatment, growth of untreated
plants resumed for all plants except those at 31 /26 C and -O.2 MPa. Plants exposed to 11/6
C did not appear stressed regardless of soil moisture.

The effect of air temperature and soil moisture on translocation of foliar applied 1‘0

nicosulfuron was examined. At least 86% of applied radioactivity was recovered from plants

81
harvested at 168 HAT (Table 6). Total 1“C recovery was not affected by soil moisture, but

increasing temperature from 21 C to 31 C reduced recovery. This difference may be
attributed to increased metabolism of herbicide to carbon dioxide in plants with increasing
temperature. Coupland (6) observed greater l“C-glyphosate metabolism to 1‘CO, in
quackgrass at 26 C than at 10 C.

Absorption and translocation of “C increased as soil moisture increased within the
21/ 16 C environment, but no significant differences were observed at 11/6 and 31/26 C
(Table 6). Despite differences in translocation at 21 / 16 C, soil moisture generally did not
influence 1‘C accumulation in individual plant parts (Table 7). Although nicosulfuron
phytotoxicity decreased with decreasing soil moisture at 21/16 and 31 /26, this response was
not explained by differences in nicosulfuron absorption, translocation, or accumulation in
vegetative reproductive tissue.

Air temperature had a significant impact on nicosulfuron distribution in quackgrass.
Within a soil moisture level, increasing air temperature significantly increased absorbed “C,
1"C in the treated leaf, and “C translocated from the treated leaf (Table 6). An
approximate two-fold increase in nicosulfuron absorption and 4-fold increase in translocation
was observed as temperature increased from 11/6 C to 31 /26 C. As a result, more
radioactivity was recovered in all plant parts as temperature increased (Table 7).
Radioactivity concentration (DPM mg") also increased with increasing air temperature.
Greater “C accumulation in vegetative reproductive tissues (crown and parent rhizome)
with increased temperature, would be expected to result in greater nicosulfuron efficacy, but
this was not observed (Table 8).

Nicosulfuron activity from 16 and 32 g ha'l applied to quackgrass was not influenced
by temperature when plants were grown with adequate (-0.03 MPa) soil moisture (Table 8).

However, quackgrass control decreased as temperature increased from 11/6 to 21 / 16 C at

82

82 @080: 05 89a 888—885 0:0
£38 85?» 28> 881888 802..
.>\> §~ 8 893.8 do 8:20..qu docs—2: 380880.: :5

 

 

 

 

 

 

_ n . N _ n m 8 838223.
m a a a a 3 8 as; was:
a. 8 2 e a a 2 Been?
m on a 8 mm a a 82688
tom—Q8 .8 as
.393 u on?” o 25 o 8: o 83“ o 28 0 e3
«32 «6. «m2 8d-

 

fl0h0>80h U:

..:o.5==m88.03 no 838888 .88 .— mg

38.—38.8 8 80:85.88 88 603988 59602 0: cc 83:28 .583 :8 88 0.888282 .8 Emmeiad .8 88.8 BF 6 88h

83

.959 55“? 23> macaw—888 :82»
.>\> §~ an 2.95:3 mo 8:30on Bun—05 8:253: =<.

 

 

 

 

 

 

 

 

c a w w 2 a 2 28s.: 22.8
cm 8 S R K on on .580
x a. 3“ t x t. 2 $2 385 320m
8 8 2 t 8 a 2 $2 8.8: 33.4.

was 2.5
S no .3 S 3. 2 2 28%: 32$
3 2 8 3 3 ed 3 €80
8 Z S Z. 3. M: .8 as. Ba»: 32%
3 2 2 S we 3 3 :2 8.8: 28¢.
Baa“ Ho 95
.053 o 85 o 23 0 £2 o 83“ 0 25 o a: .5. :33
£2 2. £2 8...-

 

«.3— 138: 05 Sew 338—88“ 0: go :o:n.=E=8<

 

raga—woman“ =o.5:=»8€.0: “can a me“
two— 3285 2: 80.: 3.8035: 0: no :ousnmbflv cc 3322. .833 :8 new 2380988 an Emu—>96 mo Some 25. N 335

.2828 5223 8 55? 23> anemia—:8 :82»
4:08.35 ban 9?.» on 33m? 833.30 33 35:00..
.>\> Q2 3 25,33 mo 8:20on ova—oi 85630: =<.

 

 

 

 

 

 

 

 

a 92.23
R R 8 S 8 8 N».
x E 3 R 8 S 2
R on on an 2. a. w
c a o c o o c
08 was mu m
u 35 o 23 o a? o 85 0 85 0 £2 2.:
cohabzmoomz
«22 ad. «m2 med-

 

L828 9.6.9.230

 

..83 0203.5; new .3888 .633 :8 .8583an as Ewmcbnau 3 8.8:.“ 3 83:38? 53 33:8 899—030 .m ”Bah

85

low soil moisture levels (-0.2 MPa), regardless of nicosulfuron application rate. Research
with chlorsulfuron (14), chlorimuron (7), and thifensulfuron (20) has shown greater
herbicidal activity at lower temperatures. However, Nalewaja and Adamczewski (13)
reported greater kochia control by thifensulfuron when day/ night temperatures were
increased from 10/8 to 30/24 C.

Soil moisture did not influence the control of plants grown at 11/6 C (Table 8).
However at 21/16 and 31 /26 C, quackgrass control generally decreased as soil water
potential decreased from -0.03 to -O.2 MPa. Oyarzabal and Owen (16) also observed
greatest nicosulfuron activity on well watered woolly cupgrass and shattercane. Kochia
control with thifensulfuron (13) and chlorsulfuron (14) was better at field capacity than when
drought stressed. However, velvetleaf control was similar with thifensulfuron regardless of
soil moisture (20).

Differences in nicosulfuron activity not explained by herbicide absorption,
translocation, or accumulation may be related to herbicide retention and differential plant
metabolism. Less herbicide may have been intercepted and retained by stressed plants.
These stressed plants likely had smaller leaf area for spray interception, due to leaf rolling.
Rossi and Neal (18) examined fenoxaprop [(i)-2-[4-[(6-chloro-2-
benzoxazolyl)oxy]phenoxy]propanoic acid] retention on moisture stressed smooth crabgrass
(Digitan'a ischaemum). They observed a 20% reduction in fenoxaprop retention as soil
moisture stress increased to -0.8 MPa. It is likely that decreased nicosulfuron retention is
contributing to decreased efficacy of moisture stressed quackgrass.

The effect of moisture stress on plant metabolism rate may also influence
nicosulfuron activity. Moisture stressed plants typically accumulate increased levels of amino
acids since slower growth rates result in decreased protein synthesis (11). As the demand

for amino acids declines in stressed plants, ALS inhibition may have a less pronounced

86

effect than in nonstressed plants where amino acid demand is high. As a result, there may
be greater accumulation of a-amino butyric acid in nonstressed plants than stressed plants
resulting in greater herbicide phytotoxicity of nonstressed plants (12,17). Future research
is needed to determine if plant moisture stress indeed influences the accumulation of «-

amino butyric acid in plants treated with an ALS inhibitor.

Acknowledgements
The authors would like to thank E. I. duPont for their generous financial support
and donation of l"C-labeled nicosulfuron. Our sincere gratitude is extended to Christy

Sprague for her technical assistance in this research.

10.

11.

12.

13.

Literature Cited

Anonymous. 1990. AccentTM Herbicide. Technical Bulletin. E. I. du Pont de
Nemours and Co. Inc., Agricultural Products Dep., Wilmington, DE. 12 p.

Beckett, T. H. and E. W. Stoller. 1991. Effects of methylammonium and urea
ammonium nitrate uptake of thifensulfuron in velvetleaf (Abutilon theophrasti).
Weed Sci. 39:333-338.

Camacho, R. F. and L. J. Moshier. 1991. Absorption, translocation, and activity of
CGA-136872, DPX-V9360, and glyphosate in rhizome johnsongrass (Sorghum
halepense). Weed Sci. 39:354-357.

Camacho, R. F., L. J. Moshier, D. W. Morishita, and D. L. Devlin. 1992. Rhizome
johnsongrass (Sorghum halepense) control in corn (Zea mays) with primisulfuron and
nicosulfuron. Weed Technol. 5:789-794.

Coupland, D and J. C. Caseley. 1979. Presence of 1“C activity in root exudates and

guttation fluid from Agropyron repens treated with l“C-labelled glyphosate. New
Phytol. 83:17-22.

Coupland, D. 1984. The effect of temperature on the activity and metabolism of
glyphosate applied to rhizome fragments of Elymus repens (=Agropyron repens).
Pestic. Sci. 15:226-234.

Edmund, R. M., Jr. and A. C. York. 1987. Effects of rainfall and temperature on
postemergence control of sicklepod (Cassia obtw'zfolia) with imazaquin and DPX-
F6025. Weed Sci. 35:231-236.

Fielding, R. J. and E. W. Stoller. 1990. Effects of additives on the efficacy, uptake
and translocation of the methyl ester of thifensulfuron. Weed Sci. 38:172-178.

Fielding, R. J. and E. W. Stoller. 1990. Effects of additives on efficacy, uptake, and
translocation of chlorimuron ethyl ester. Weed Technol. 4:264-271.

Holm, L. G., D. L. Plucknett, J. V. Pancho, and J. P. Herberger. 1977. The World’s
Worst Weeds: Distribution and Biology. University Press of Hawaii, Honolulu. 609

PP-

Hsiao, T. C. 1973. Plant response to water stress. Ann. Rev. Plant Physiol. 24:519-
570.

LaRossa, R. A., T. K. Van Dyk, and D. R. Smulski. 1987. Toxic accumulation of
a-ketobutyrate caused by inhibition of the branched-chain amino acid biosynthetic
enzyme acetolactate synthase in Salmonella typhimurium. J. Bacteriol. 169:1372-
1378.

Nalewaja, J. D. and K. A. Adamczewski. 1988. Thiameturon phytotoxicity to kochia
(Kochia scopan’a). Weed Science 36:296-300.

87

14.

15.

16.

17.

18.

19.

20.

88

Nalewaja, J. D. and Z. Wonzica. 1985. Environment and chlorsulfuron
phytotoxicity. Weed Sci. 33:395-399.

Obrigawitch, T. A., W. H. Kenyon, and H. Kuratle. 1990. Effect of application
timing on rhizome johnsongrass (Sorghum halepense) control with DPX-V9360.
Weed Sci. 38:45-49.

Oyarzabal, E. S. and M. D. K. Owen. 1992. Nicosulfuron and primisulfuron-methyl
activity in shattercane (Sorghum bicolor) and woolly cupgrass (Eriochloa villosa)
grown under water stress. Abstr. Weed Sci. Soc. Am. 32:5.

Rhodes, D., A. L. Hogan, L. Deal, G. C Jamieson, and P. Haworth. 1987. Amino
acid metabolism of Lemna minor 1... H. Responses to chlorsulfuron. Plant Physiol.
84:775-780.

Rossi, F. S. and J. C. Neal. 1991. Fate of fenoxaprop applied to moisture stressed
crabgrass (Digitaria ischaeum) Abstr. Weed Sci. Soc. Am. 31:56.

Thompson, M. A., W. W. Witt, J. R. Martin, and C. H. Slack. 1989. The efficacy
of DPX-V9360 and CGA-136872 on johnsongrass (Sorghum halepense) control in
corn. Abstr. Weed Sci. Soc. Am. 29:4.

Zhao, C. C., J. R. Teasdale, and C. B. Coffman. 1990. Factors affecting the activity
of thifensulfuron. Weed Sci. 38:553-557.