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WEED MANAGEMENT PROGRAMS FOR USE IN HERBICIDE
RESISTANT- SUGARBEET

presented by

Nathan Joseph Kemp

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14.8.. . CrOp and Soil Sciences

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11/00 chIHCIDIbOUOpGS-p.“

WEED MANAGEMENT PROGRAMS FOR USE
IN HERBICIDE RESISTANT SUGARBEET

By

Nathan Joseph Kemp

A THESIS
Submitted to
Michigan State University
in partial fulﬁllment of the requirements
for the degree of
MASTER OF SCIENCE
Department of Crop and Soil Sciences

2000

ABSTRACT

WEED MANAGEMENT PROGRAMS FOR USE IN
HERBICIDE RESISTANT SUGARBEET

By

Nathan Joseph Kemp

The recent introduction of sugarbeet modiﬁed to express resistance to the
herbicides glufosinate and glyphosate provides a new method for weed management in
this crop. Traditional weed management systems in sugarbeet follow a program
approach utilizing preemergence herbicides, postemergence herbicides, cultivation, and
hand-labor. Unlike conventional sugarbeet herbicides, glufosinate and glyphosate
applied in herbicide resistant sugarbeet can effectively control weeds that exceed 5 cm in
height, produce no crop injury, and eliminate the need for manual or mechanical weed
control. Research was conducted in 1998 and 1999 as a cooperative effort between
Michigan State University, Michigan Sugar Company, and Monitor Sugar Company to
evaluate the use of glufosinate and glyphosate in sugarbeet production. Herbicide
resistant sugarbeet was planted at four locations in Michigan each of two years. Research
determined when annual weeds became competitive with sugarbeet, the need for using
preemergence herbicides prior to postemergence applications of glufosinate or

glyphosate, and the effect of cultivation on annual weed emergence.

ACKNOWLEDGMENTS

This section of my thesis may have been the most difficult to write since there are
so many people who deserve credit for my accomplishment. I would like to thank Dr.
Merrill Ross and Dr. Carole Lembi for being mentors as well as friends. If it were not for
them I would have never continued my education. I also need to thank Richie and Mike
for getting me through the Purdue years. A project such as this could not have been
completed without the selﬂess hours given by my fellow graduate students, undergrads,
and technicians in the program. G. Powell, Kyle, Kelly, Sherri, Chad, Jason, Andy,

Dr. Sprague, Bart, Caleb, Joe, Amy, Biff, Pat, & Heather, you guys are the greatest. I
think of our crew as being more like family then friends or colleagues. I need to
especially thank my major Professor, Dr. Karen Renner, for her guidance and for giving
me the opportunity to come to Michigan State. My time in Michigan has truly been a life
altering experience. Dr. Kells, Dr. Saunders, Dr. Christenson, Dr. Black, and of course
Doc Penner were always there when I had a question or needed help. I also need to
acknowledge both the Michigan and Monitor Sugar Companies, whose support made this
project possible. Tre, Lee, Rick and the crew, thank you. I can not forget the person who
made the largest contributions to this assignment. Julie, you have given up more for this
project then anyone realizes. Always supportive, never forgetting that our ﬁxture was

bright. Within these pages is only one chapter of our lives, the rest of the book has yet to

be written.

iii

TABLE OF CONTENTS
LIST OF TABLES ................................................................................... vi
LIST OF FIGURES .................................................................................. x

Chapter 1. REVIEW OF LITERATURE

INTRODUCTION ........................................................................... 1
GLYPHOSATE AND GLUFOSINATE ................................................. 3
INCREASED USE OF HERBICIDES IN SUGARBEET PRODUCTION ......... 5
SUGARBEET INJURY FROM HERBICIDES ......................................... 6
THE BASIS FOR WEED COMPETITION ............................................. 7
Effect of Weeds on Sugarbeet Yield and Quality .............................. 8
Critical Period for Weed Control ................................................. 9
Sugarbeet Tolerance to Weed Competition .................................... 10

Time of Weed Emergence ....................................................... 11
Competitiveness of Various Species ............................................ 12

Weeds within the Row ............................................................ l4
PROGRAM APPROACH TO WEED CONTROL IN SUGARBEET ............. l4
WEED EMERGENCE AND CULTIVATION ........................................ 16
WILL HERBICIDE RESISTANT CROPS LEAD TO RESISTANT WEEDS?..19
LITERATURE CITED .................................................................... 25
Chapter 2. COMPETITIVENESS OF ANNUAL WEEDS IN HERBICIDE RESISTANT

SUGARBEET
ABSTRACT ................................................................................. 31
INTRODUCTION ......................................................................... 32
MATERIALS AND METHODS ......................................................... 34
RESULTS AND DISCUSSION ......................................................... 37
CONCLUSION ............................................................................. 40
LITERATURE CITED .................................................................... 42
Chapter 3. USE OF PREEMERGENCE HERBICIDES WITH HERBICIDE
RESISTANT SUGARBEET

ABSTRACT ................................................................................. 59
INTRODUCTION ......................................................................... 60
MATERIALS AND METHODS ......................................................... 62
RESULTS AND DISCUSSION ......................................................... 65
Full versus Half Rates ............................................................ 65

Delay in Postemergence Applications .......................................... 66

Need for Additional Postemergence Application ............................. 66
Conventional Postemergence Programs ....................................... 68
Sugarbeet Yield .................................................................... 68

iv

Cost Comparison .................................................................. 69
CONCLUSION ............................................................................. 71
LITERATURE CITED .................................................................... 73

Chapter 4. EFFECT OF CULTIVATION ON WEED EMERGENCE IN
GLUFOSINATE RESISTANT SUGARBEET

ABSTRACT ................................................................................. 89
INTRODUCTION ......................................................................... 90
MATERIALS AND METHODS ......................................................... 93
RESULTS AND DISCUSSION ......................................................... 95
CONCLUSION ............................................................................. 96
LITERATURE CITED .................................................................... 98
APPENDICES ..................................................................................... 1 1 5

LIST OF TABLES

Chapter 2. COMPETITIVENESS OF ANNUAL WEEDS IN HERBICIDE RESISTANT
SUGARBEET

Table 1 - Minimum weed densities that are reported to be competitive and reduce
sugarbeet root yield or recoverable sucrose ................................. 44

Table 2 — Soil series, type, organic matter, and planting dates for glufosinate and
glyphosate resistant sugarbeet at each location in 1998 and 1999 ........ 45

Table 3 -— Growth stage of sugarbeet and weed height at various weeks after
planting in 1998 and 1999 ..................................................... 46

Table 4 — Number of common lambsquarters, redroot pigweed, and mixed
species per 30 m in row of glyphosate or glufosinate resistant
sugarbeet for the Michigan State University, Michigan Sugar Co., and
Monitor Sugar Co. sites in 1998 and 1999 ................................. 47

Table 5 — Glyphosate resistant sugarbeet root and sugar yield in 1998 and 1999,
combined over two locations ................................................. 48

Table 6 - Glufosinate resistant sugarbeet root and sugar yield in 1998 and 1999,
combined over two and three locations respectively ...................... 49

Chapter 3. USE OF PREEMERGENCE HERBICIDES WITH HERBICIDE
RESISTANT SUGARBEET

Table 7 — Soil series, type, organic matter, and planting dates for glufosinate and
glyphosate resistant sugarbeet at each location in 1998 and 1999 ....... 74

Table 8 — Dates of first glyphosate and glufosinate application following
preemergence applications of cycloate, ethofumesate, and pyrazon at
the Michigan State University, Michigan Sugar Co., and Monitor Sugar
Co. sites in 1998 and 1999 .................................................... 76

Table 9 — Common lambsquarters and redroot pigweed control and root yield of
herbicide resistant sugarbeet following preemergence applications of
cycloate, ethofumesate, pyrazon, or no preemergence herbicide
followed by postemergence applications of glyphosate or glufosinate at
the Michigan State University and Monitor Sugar sites in 1999. . . . . . ...78

Table 10 — Control of common lambsquarters and redroot pigweed at the

Michigan State University, Michigan Sugar, and Monitor Sugar sites
in 1998 and 1999 from cycloate, ethoﬁirnesate, pyrazon, or no
herbicide preemergence each followed by glyphosate .................. 80

Table 11— Control of common lambsquarters and redroot pigweed at the

Michigan State University, Michigan Sugar, and Monitor Sugar sites in
1998 and 1999 from cycloate, ethofumesate, pyrazon, or no herbicide
preemergence each followed by glufosinate .............................. 82

Table 12 — Control of common lambsquarters and redroot pigweed at the

Michigan State University and Monitor Sugar sites in 1998 and the
Michigan State University, Michigan Sugar, and Monitor Sugar sites
in 1999 from cycloate, ethoﬁimesate, pyrazon, or no preemergence
herbicide followed by desmedipham and phenmedipham plus

triﬂusulfuron plus clopyralid applied to glyphosate and glufosinate
resistant sugarbeet ............................................................ 84

Table 13 — Root yield and recoverable sucrose of sugarbeet following application

of cycloate, ethoﬁlmesate, pyrazon, or no preemergence herbicide
followed by glyphosate at the Michigan Sugar and Monitor Sugar sites
in 1998 and the Michigan State University site in 1999 ................. 86

Table 14 - Root yield and recoverable sucrose of sugarbeet following application

of cycloate, ethofumesate, pyrazon, or no preemergence herbicide
followed by glufosinate at the Michigan Sugar and Monitor Sugar sites
in 1998 and the Michigan State University and Monitor Sugar sites in
1999 .............................................................................. 88

Chapter 4. EFFECT OF CULTIVATION ON WEED EMERGENCE IN HERBICIDE
RESISTANT SUGARBEET

Table 15 — Description of cultivation treatments and timings in 1998 and

APPENDIX

1999 ........................................................................... 100

Table 16 — Yield and control of common lambsquarters, redroot pigweed,

and velvetleaf with pyrazon, ethoﬁimesate, or cycloate followed by

postemergence applications of glyphosate to sugarbeet at the Michigan
Sugar Co. site in 1998 ...................................................... 116

Table 17 — Yield and control of common lambsquarters, redroot pigweed, and

velvetleaf with pyrazon, ethofumesate, or cycloate followed by
postemergence applications of glufosinate to sugarbeet at the
Michigan Sugar Co. site in 1998 .......................................... 117

vii

Table 18 — Yield and control of common lambsquarters and redroot pigweed with
pyrazon or ethofumesate followed by postemergence applications of
glyphosate to sugarbeet at the Monitor Sugar Co. site in 1998 ....... 1 18

Table 19 - Yield and control of common lambsquarters and redroot
pigweed with pyrazon or ethofumesate followed by postemergence
applications of glufosinate or desmedipham and phenmedipham plus
triﬂusulfuron plus clopyralid to sugarbeet at the Monitor Sugar Co.
site in 1998 ................................................................... 119

Table 20 — Control of common lambsquarters, redroot pigweed, and
Pennsylvania smartweed in glyphosate resistant sugarbeet at the
Saginaw Valley Bean & Beet Farm in 1998 .............................. 121

Table 21 — Control of common lambsquarters, redroot pigweed, velvetleaf,
and Pennsylvania smartweed in glufosinate resistant sugarbeet at the
Saginaw Valley Bean & Beet Farm in 1998 .............................. 123

Table 22 - Sugarbeet injury, yield, and control of common lambsquarters and
redroot pigweed with pyrazon, ethofumesate, or cycloate followed by
postemergence applications of glyphosate or desmedipham and
phenmedipham plus tn'ﬂusulfuron plus clopyralid to sugarbeet at the
Michigan Sugar Co. site in 1999 .......................................... 125

Table 23 - Sugarbeet injury, yield, and control of common lambsquarters and
redroot pigweed with pyrazon, ethofumesate, or cycloate followed by
postemergence applications of glufosinate or desmedipham and
phenmedipham plus tn'ﬂusulfuron plus clopyralid to sugarbeet at the
Michigan Sugar Co. site in 1999 .......................................... 127

Table 24 - Sugarbeet injury and control of annual grass, common lambsquarters,
and redroot pigweed with ethofumesate or pyrazon followed by
glyphosate or desmedipham and phenmedipham plus triﬂusulfuron
plus clopyralid in sugarbeet at Monitor Sugar Co. site in 1999 ....... 129

Table 25 — Sugarbeet injury, yield, and control of annual grass, common
lambsquarters and redroot pigweed with ethoﬁimesate or pyrazon
followed by postemergence applications of glufosinate or

desmedipham and phenmedipham plus triﬂusulfuron plus clopyralid to
sugarbeet at the Monitor Sugar Co. site in 1999 ......................... 131

Table 26 — Sugarbeet injury, yield, and control of common lambsquarters and
redroot pigweed with pyrazon, ethofumesate, or cycloate followed by
postemergence applications of glyphosate or desmedipham and
phenmedipham plus triﬂusulfuron plus clopyralid to sugarbeet at the
Saginaw Valley Bean and Beet Farm in 1999 ........................... 133

viii

Table 27 — Sugarbeet injury, yield, and control of common lambsquarters and
redroot pigweed with pyrazon, ethoﬁimesate, or cycloate followed by
postemergence applications of glufosinate or desmedipham and
phenmedipham plus triﬂusulfuron plus clopyralid to sugarbeet at the
Saginaw Valley Bean and Beet Farm in 1999 ........................... 135

ix

LIST OF FIGURES

Chapter 2. COMPETITIVENESS OF ANNUAL WEEDS IN HERBICIDE RESISTANT
SUGARBEET

Figure 1 — Illustration of an average critical weed control period for sugarbeet
(sources: Dawson 1965, Weatherspoon and Schweizer 1969, Wicks
and Wilson 1983, Van Heemst 1985, Schweizer and May 1993) ...... 50

Figure 2 - Inﬂuence of a) weed density and b) weed biomass on the root yield of
sugarbeet from nine studies in 1998 and 1999 ............................. 51

Figure 3 — Root yields for a) glyphosate resistant sugarbeet averaged over two
sites, and b) glufosinate resistant sugarbeet averaged over two sites,
where weeds were removed at various heights and weed-free
conditions were then maintained by the herbicide in 1998 ............... 52

Figure 4 — Root yields for a) glyphosate resistant sugarbeet averaged over two
sites, and b) glufosinate resistant sugarbeet averaged over three sites,
where weeds were removed at various heights and weed-free
conditions were maintained by the herbicide in 1998 .................... 53

Figure 5 — Root yield of a) glyphosate and b) glufosinate resistant sugarbeet and
weed biomass in 1998 where weed control was maintained for
progressively longer periods after crop emergence ....................... 54

Figure 6 — Root yield of a) glyphosate and b) glufosinate resistant sugarbeet and
weed biomass in 1999 where weed control was maintained for
progressively longer periods after crop emergence ....................... 55

Figure 7 — Critical weed control period for a) glyphosate and b) glufosinate
resistant sugarbeet in 1998 ................................................... 56

Figure 8 — Critical weed control period for a) glyphosate and b) glufosinate
resistant sugarbeet in 1999 ................................................... 57

Figure 9 — Example of the timing for either glyphosate or glufosinate applications
to prevent loss of root and sugar yield in sugarbeet ...................... 58

Chapter 4. EFFECT OF CULTIVATION ON WEED EMERGENCE IN HERBICIDE
RESISTANT SUGARBEET

Figure 10 — Effect of cultivation timing on the emergence of annual weeds in
glufosinate resistant sugarbeet in 1998 ................................. 102

Figure 11 - Effect of cultivation timing on the emergence of common
lambsquarters in glufosinate resistant sugarbeet in 1998 ............. 104

Figure 12 — Effect of cultivation timing on the emergence of annual grass in
glufosinate resistant sugarbeet in 1998 .................................. 106

Figure 13 — Effect of cultivation timing on the emergence of annual weeds in
glufosinate resistant sugarbeet in 1999 .................................. 108

Figure 14 — Effect of cultivation timing on the emergence of common
lambsquarters in glufosinate resistant sugarbeet in 1999 ............ 110

Figure 15 - Effect of cultivation timing on the emergence of annual grass in
glufosinate resistant sugarbeet in 1999 .................................. 112

Figure 16 — Effect of cultivation timing on the emergence of annual
smartweeds in glufosinate resistant sugarbeet in 1999 ................ 114

xi

Chapter 1
Review of Literature

Introduction

Sugarbeet (Beta vulgaris L.) belongs to the botanical family Chenopodiaceae.
Sugarbeet is characterized with a biennial growth habit; since the production of seed
usually requires some period of thermal induction in which the plant must be exposed to a
period of low temperatures (WCBSC 1990). The sugarbeet root is harvested for the
production of sugar, although molasses and pulp are saleable byproducts. Approximately
37% of world sugar is derived from sugarbeet, making it the most important sucrose
producing crop in temperate regions (D’Halluin et a]. 1992). Sugarbeet is grown under a
production contract in which the processor receives sugarbeet root produced on a
speciﬁed piece of ground at an established pricing agreement. In Michigan the grower is
paid a percentage of the revenue that the sugar companies generate from the sale of sugar.
This payment is based upon the tons of sugarbeet root produced and delivered. A
premium or deduction is based upon the relative sugar content of these roots (Michigan
Sugar Company, 1999 Grower Contract).

In the United States there are ﬁve general geographic regions where sugarbeet is
grown. These regions include the Great Plains, the Red River Valley, the Northwest,
California, and the Great Lakes. Together these regions have approximately 470,000 ha
of land in production (Schweizer and Dexter 1987). Even within these ﬁve regions there
are differences in agronomic, ecological, and climatic conditions. There is also a
differentiation between irrigated and non-irrigated land. Sugarbeet in Michigan is

produced under non-irrigated conditions. In 1997 approximately 66,000 ha of sugarbeet

was planted in Michigan resulting in over 2.7 million metric tons of harvested sugarbeet
root (MASS 1998).

The recent development of sugarbeet varieties that are resistant to the herbicides
glyphosate (N—phosphonomethylglycine) or glufosinate (2-amino-4-hydroxymethyl
phosphinyl butanoic acid) has introduced the ﬁrst substantial change in weed control
programs for this crop in over 25 years. Most of the herbicides currently used in
sugarbeet production were developed in the late 1960’s and have a narrow margin of
selectivity. Changes in environmental conditions can alter their phytotoxic effects,
producing crop injury (Schweizer and Dexter 1987). Besides causing injury, traditional
sugarbeet herbicides have the ability to control only very small weeds when applied
postemergence (Wilson 1998). The precise timing required and the need for multiple
reduced rate applications to avoid crop injury make current postemergence treatments less
than ideal. In spite of this there has been a gradual shiﬁ towards the use of more
postemergence products (Grifﬁth 1994). Unlike traditional postemergence sugarbeet
herbicides, glyphosate and glufosinate do not injure the resistant crop and have the ability
to kill large weeds, making this technology the next step in the evolution of weed control
programs.

In 1965 it was estimated that weed competition in the United States caused a loss
in yield and quality equal to eight percent of the potential value of sugarbeet (Schweizer
1981). At that time only 33% of sugarbeet acres were treated with herbicides. From
1975-1979 weeds accounted for a 10% yield loss in sugarbeet. This resulted in an
approximately $89 million loss (Schweizer and Dexter 1987). In 1984 approximately

90% of the sugarbeet acres received a herbicide treatment (Schweizer and Dexter 1987).

Despite this increase in herbicide use, and presumably the increased weed control that
would be associated with this use, weeds continued to cause economic loss. More current
estimates of economic loss are $350 million when no herbicides are applied and $60
million when best management practices are implemented (Morishita and Downard
1995). These crop losses are not due to new weed species invading U.S. sugarbeet
growing regions, but are caused from inadequate control of common species. A 1985
survey listed pigweeds (Amaranthus spp.), common lambsquarters (Chenopodium album
L.), kochia (Kochia scoparia L.), and smartweeds (Polygonum spp.) as the major
broadleaf weeds in sugarbeet, with other species such as velvetleaf (Abutilon theophrasti
Medic.) and nightshades (Solanum spp.) also becoming a problem (Schweizer and Dexter
1987). These weeds are among the most difﬁcult to control in sugarbeet (Morishita and

Downard 1995).
Glyphosate & Glufosinate

Glyphosate and glufosinate have herbicidal activity on most species of plants and
can only be used for postemergence weed control in genetically altered, resistant crop
varieties. Crops that are resistant to glyphosate are sold under the trademark Roundup
Ready®; glufosinate resistant crops are known as Liberty Link®. Though both of these
herbicides are in the same chemical family, each has a unique mode of action and can
only be applied to the appropriate resistant variety. Resistance genes for these herbicides
have been inserted into canola, corn, cotton, rice, soybean, and sugarbeet varieties
(WSSA 1997). Glyphosate and glufosinate do not remain active in the soil, so there is

no risk of herbicide carryover into other crops (WSSA 1994). There is also no residual

effect on later emerging weed seedlings. Glyphosate is rapidly and tightly adsorbed to
the soil and is therefore inactivated (Delannay et al. 1995).

Glufosinate is mobile in the soil; however, soil microbes rapidly degrade this
herbicide (W SSA 1994). Glufosinate (2-amino-4-hydroxymethylphosphinyl butanoic
acid) inhibits the enzyme glutamine synthase (D’Halluin et al. 1992, WSSA 1994). This
enzyme facilitates the conversion of glutamate and ammonia to glutamine (WSSA 1994,
Taiz and Zeiger 1998). When glutamine synthase is inhibited the plant is not able to
assimilate ammonium. Accumulation of ammonia is toxic to plant cells and directly
inhibits photosystem I and 11 reactions (W SSA 1994). The insertion of a synthetic
phosphinothricin—N-acetyl transferase or PAT gene via Agrobacterium tumefaciens
mediated transformation allows the crop plant to rapidly metabolize glufosinate
(D’Halluin 1992, WSSA 1994, AgroEvo USA Company).

Glyphosate (N-phosphonomethyl glycine) inhibits the enzyme 5-
enolpyruvylshikimate-B-phosphate synthase or EPSP synthase (WSSA 1994, Delannay et
al. 1995, Padgette et al. 1995). The inhibition of this enzyme does not allow 5-
enolpyruvylshikimate-3-phosphate or EPSP to be produced from shikimate—B-phosphate
and phosphoenolpyruvate in the shikimic acid pathway. This is part of the aromatic
amino acid biosynthetic pathway, which is responsible for the production of tryptophan,
tyrosine, and phenylalanine (WSSA 1994, Padgette et al. 1995). EPSP synthase is
present only in plants, bacteria, and fungi (Delannay et a1. 1995). Glyphosate is not
readily metabolized within the plant (WSSA 1994). Herbicide resistance is accomplished

through the insertion of a gene that encodes an insensitive target protein. Glyphosate

does not bind to this tolerant EPSP synthase and the plant continues to produce aromatic

amino acids (Padgette et al. 1995).
Increased use of herbicides in sugarbeet production

Limiting crop losses due to weeds is only one reason for increased herbicide use
in sugarbeet. There are also many intangible reasons to use herbicides, such as aesthetic
value, reduced weed seed production, and elimination of harbored pests (Schweizer and
Dexter 1987). Another reason for the increased use of herbicides in sugarbeet is related
to the cost of labor. Traditionally weeds were removed from the crop using hand labor
and cultivation. The cost of hiring people to hand hoe a crop is increasing (Wilson 1994).
Between 1970 and 1986 the cost of labor doubled (Schweizer and Dexter 1987).
Herbicides also increased in cost, but still cost less then labor for removing weeds. This
is especially true in ﬁelds with many weeds (Schweizer and Dexter 1987). Miller and
Fomstrom (1989) reported that herbicide treatments reduced weed control costs
compared with labor alone. The beneﬁt of using herbicides ranged from $77 - $152 per
acre, with the greatest return from preemergence herbicides used in combination with
postemergence herbicides. Their studies showed that it required 4.4 hours per acre to
walk through a weed free ﬁeld twice, and an additional 0.5 hours per acre to remove 1000
weeds (Miller and Fomstrom 1989). As the cost of labor increased, the use of herbicides
became essential for minimizing weed control costs. It is for this reason that sugarbeet

producers in the US. rely on herbicides and cultivation for weed control.

Sugarbeet injury from herbicides

Herbicides used in sugarbeet production can injure the crop as well as control
weeds. Loss of crop vigor can range from 0% to 3% for either preemergence or
postemergence programs. A combined program using both preemergence and
postemergence products caused as much as 15% visible injury to sugarbeet (Miller and
Fomstrom 1989). Though this injury is signiﬁcant, sugarbeet recovery was excellent,
with yield or percent sucrose in the herbicide-treated sugarbeet being statistically similar
to the hand-weeded control (Miller and Fomstrom 1989). Sugarbeet exhibits variable
crop tolerance to conventional sugarbeet herbicides. Sugarbeet genotypes differ in their
tolerance to cycloate or ethofumesate followed by desmedipham and phenmedipham
(Smith et al. 1982, Smith and Schweizer 1983). Sugarbeet tolerance to EPTC differed by
cultivar (Dexter and Kern 1977, Schweizer and Dexter 1987).

Many herbicides that are used in other crops have the ability to injure sugarbeet.
Residual products that can harm sugarbeet include chlorsulfuron (2-chloro-N-[[(4-methyl-
6-methyl-l,3,5-triazin-2yl)amino]carboxyl]benzenesulfonamide), dicarnba (3,6-dichloro-
2-methoxybenzoic acid), metribuzin (4-amino—6-(l ,1-dimethyl)-3-(methythio)—l ,2,4-
triazin-5(4H)-one), pendimethlin (N-(l-ethylpropyl)-3,4—dimethyl-2,6-
dinitrobenzenarnine), picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid),
triﬂuralin (2,6-dinitro-N,N—dipropyl-4-(tn'ﬂuoromethyl)benzenarnine), and atrazine (6-
chloro-N-ethyl-N-( 1-methylethyl)l,3,5-t1iazine—2,4,-diamine) (Schweizer and Dexter
1987, Dexter et al. 1994). One of the most detrimental herbicides is irnazethapyr (2[4,5-
dihydro-4-methyl-4-(l-methylethyl)-5-oxo-lH-imidazol-Z-yl] 5-ethyl-3-

pyridinecarboxylic acid), which has the ability to injure sugarbeet for 40 months after

application (Renner and Kells 1999). Crop injury from residual herbicides occurs most
frequently on sandy or low organic matter soils. Carryover problems can be lessened
with plowing, or by avoiding excessive herbicide rates.

Residual herbicide from application in other crops in the rotation is not the only
way sugarbeet can be injured. Crop yield or quality can also be affected by inadvertent
exposure due to herbicide drift or volatilization. An excellent example would be
exposure of sugarbeet to the herbicides 2,4-D ((2,4-dichlorophenoxy) acetic acid) and
dicamba (Schweizer 1978, Schroader et al. 1983). These herbicides not only reduce root
yield, but can also cause sucrose loss during post harvest storage. The level of impact
depends on the growth stage of the crop and the herbicide concentration at the time
exposure. Sugarbeet exposed to these herbicides should be processed immediately after

harvest and not placed in piles (Schweizer 1978, Schroeder et al. 1983).
The Basis for Weed Competition

The basis for weed competition in crops is that a plant will only compete with
another plant when there are one or more limiting resources. In the ﬁeld the basic
resources limiting crop growth are nutrients, water, and light (Kropff 1988). In most ﬁeld
situations nutrients are provided in the form of fertilizer, where the grower controls the
amount of nutrients applied. In arid regions water may become the most limiting
resource; however, in these areas sugarbeet is grown under irrigation. In irrigated beets
where water and nutrients are plentiful, competition for these resources does not occur
early in the growing season. Therefor competition for light is the main factor causing a
yield loss due to weeds (Brimhall et al. 1965, Dawson 1965, Schweizer and Bridge

1982). It is only after a weed dominates light interception that weeds gains a competitive

advantage and become more effective in water and nutrient uptake (Dawson 1970). The
period of weed competition that a crop can tolerate is inﬂuenced by the vigor of the weed
species and the speciﬁc environmental resource the plants are in competition for. As long
as the only limited resource is light, then the crop can tolerate weeds for a fairly long time
(Dawson 1970).

E t eet Yield and it

Yield loss in sugarbeet due to weed competition can be attributed to the decrease
in diameter and not the length of sugarbeet roots (Brimhall et al. 1965). The effect of
weeds on recoverable sugar per acre/hectare is a direct result of decreased root yield,
since weed density does not affect percent sucrose or purity of brei (Brimhall et al. 1965,
Zirndahl and F ertig 1967, Schweizer and Bridge 1982).

The competition of weeds with sugarbeet has the ability to decrease not only the
weight of harvested roots, but also affects the growth of beet tops. This loss of weight is
not offset by the gain in weed growth (Schweizer 1981, Schweizer 1983). The biomass
of a speciﬁc weed-beet community is less then that of a weed-free community (Schweizer
and Bridge 1982). For every 1120 kg/ha of above ground weed biomass that was
produced there was a corresponding yield decrease of 10500 to 11600 kg/ha (Wicks and
Wilson 1983). Weed biomass at any stage is inﬂuenced by weed species composition
(Bond and Burton 1996). It is important to note that limiting resources such as moisture
and light are critical for both weeds and the crop.

Weed biomass from areas where weed density has been reduced is comparable to
that of an unweeded control (Miller and Hopen 1991). The effect of weed density is

minimized by the increased growth of the remaining weeds (Brimhall et al. 1965,

Zimdahl and Fertig 1967). The total biomass of Setariafatua and A. hybridus stayed
constant in corn and soybean crops, despite differences in weed densities (Schweizer
1983). The average weight of weeds such as K. scoparia is affected by weed density only
when the density is equal to one or more plants per 2 foot of row (Weatherspoon and
Schweizer 1971).

Critical Period for; Weed Control

There have been two traditional types of weed competition studies. To determine
when weeds can infest the crop, a weed free period is maintained for various time
intervals after crop emergence. After this initial weed-free period, weeds are allowed to
remain in the crop. To determine how long weeds can remain in the crop from the time
of crop emergence, weeds are allowed to grow uninterrupted initially, and are then
removed at various stages in the development of the crop and continually removed until
the end of the growth cycle (Van Heemst 1985). Performing these types of studies allows
the researcher to determine the critical period for weed control in a crop. The critical
period is the time during the crop lifecycle in which the presence of weeds has the
strongest effect on yield (Van Heemst 1985).

Dawson (1970) described two stages associated with full season weed control.
During stage one the grower must provide weed control via tillage, herbicides, or hand
labor. Stage one is shorter where fast growing crops are planted in warm conditions, or
when nutrients and water are scarce. This ﬁrst stage will persist longer if crops are
planted during cool weather. The period of time during which crops can tolerate weeds
becomes shorter if planting is delayed. This is because warmer temperatures allow weeds

to grow rapidly. This period may become even shorter if moisture is in short supply. As

an example, wheat and ﬂax grown in semi-arid regions can only tolerate two weeks of
weed competition. In contrast, sugarbeet grown under irrigation in these regions can
tolerate weeds for eight to 12 weeks after planting or ﬁve to nine weeks after crop
emergence (Dawson 1965, Dawson 1970). Sugarbeet withstands this lengthy period of
competition when the crop is planted early and water is in adequate supply (Dawson
1970)

Stage two begins when crop dominance is established over weeds after being
favored by weed control practices. The length of this stage can vary according to crop
stand and vigor; however, vigor of weeds has no effect when this stage begins (Dawson
1970). As an example, during the ﬁrst ten to 12 weeks of sugarbeet growth a grower
should apply weed control practices, while the crop controls weeds that emerge later
(Zirndahl and Fertig 1967). Competition for light appears to be responsible for
suppression of new weeds by beets from ten to 12 weeks until harvest (Dawson 1965).
The crop is a signiﬁcant part of season-long weed control. The critical point in the
season at which the crop can suppress weeds is determined by each crop situation
(Dawson 1970).

et 1 etoWe om ti'on

There are several theories for how long weeds can remain in sugarbeet. Moisture
and relative date of beet emergence are critical factors in determining the degree of
competition. Weed competition for 24 to 28 days after crop emergence had no effect on
sugarbeet yield in Wyoming (Brimhall er al. 1965). Sugarbeet can tolerate weeds for two
to eight weeks after emergence depending on weed species, emergence of weeds relative

to crop emergence, and environmental conditions (Scott et al. 1979, Schweizer and May

10

1993). Yield is drastically decreased only when weeds are allowed to remain in the crop
for the duration of the season.

Weeds were most competitive if they emerged within eight weeks after planting
(Wicks and Wilson 1983, Wilson 1992) or within four weeks after the crop reached the
two-leaf stage (Wicks and Wilson 1983, Schweizer and Dexter 1987, Schweizer and May
1993). Research that supports this idea has shown that E. crus-galli and A. retroﬂexus,
which emerge at the end of June, were not competitive with the sugarbeet crop (Dawson
1974, Schweizer and Dexter 1987). Studies by Dawson (1965) showed that maximum
sugarbeet yield was achieved if weed control was maintained for eight to 12 weeks after
planting or ﬁve to 9 weeks after crop emergence. Maintaining weed control for ﬁve
weeks after time of emergence may not be long enough. When K. scoparia was removed
at this time sugarbeet yield was still lost (Weatherspoon and Schweizer 1969). One K.
scoparia per 4.8 foot of row was able to emerge and cause a 2.7 ton per acre loss in
harvested root yield. In contrast, full season competition from early emerging weeds
resulted in a yield loss of 9.2 tons per acre (Weatherspoon and Schweizer 1971). Though
later emerging weeds decreased sugarbeet yield, the loss was considerably less then that
from ﬁrll season competition. The ability for sugarbeet to compete with late emerging
weeds is diminished if the crop is not at normal vigor or full stand (Dawson 1974,
Schweizer and Dexter 1987).

Time of Weed Emergence

The relative dates of emergence were important in determining the competitive

efﬁciency of weeds and sugarbeet (Zimdahl and Fertig 1967, Kropff 1988). Weeds that

emerge early are troublesome and have the most potential to cause yield loss in sugarbeet

ll

(Dawson 1965, Weatherspoon and Schweizer 1969, Wicks and Wilson 1983). Variation
accounted for by weed density was 13%, whereas differences in the period between crop
and weed emergence explained 96% of variation in yield loss between experiments
(Kropff 1988). Weeds that emerge early have the opportunity to grow for a longer period
of time before the sugarbeet canopy is formed. This can be thought of as a race in which
each species must shade the other ﬁrst in order to win. An excellent example of a weed
that is competitive with sugarbeet is C. album. Dawson has shown that season-long
competition from C. album has the ability to reduce sugarbeet yield by 94% (Dawson
1965, Zirndahl and F ertig 1967). This species grows tall, provides dense shade, and tends
to emerge with sugarbeet. Another problem weed A. retroﬂexus also grows tall and
dense. This weed however, does not have as great an effect on yield as C. album. The
presence of C. album was associated with 86% of sugarbeet yield variability, whereas the
presence of both C. album and A. retroﬂexus explained 91% of yield variability (Wicks
and Wilson 1983). A. retroﬂexus is not as competitive with sugarbeet due to a later date
of emergence (Dawson 1965). Also, C-4 plants like A. retroﬂexus are more competitive
in warmer climates, while C-3 plants such as C. album are suited to cooler climates.
However, if either of these weed species emerge before the crop, they will become
competitive more quickly (Dawson 1965).

Cgmetig'veness 9f Vm’gus Species

The time of weed emergence is not the only factor that can inﬂuence a plants ability to
compete for light. In sugarbeet, broadleaf weeds are more damaging to yield then grassy
weeds (Brimhall et al. 1965, Dawson 1965, Schweizer and Dexter 1987). This is because

broadleaf weeds such as C. album have wider leaves, which provide dense shade

12

(Dawson 1965). E. crus-gallr' reduced sugarbeet yield by 49% compared to 94% for C.
album (Dawson 1965, Zimdahl and Fertig 1967, Schweizer and Dexter 1987). C. album
emerged ﬁrst and remained the dominant competitor though E. crus-galli was more
numerous. Two broadleaf weeds had a greater effect on sugarbeet yield than 20 grasses
(Zirndahl and Fertig 1967). As the season progressed, individual weeds became fewer as
the older, larger ones crowd the others. When comparing full season competition
between the two weed species, E. crus-galli lost 70% of its yield compared with 13% for
C. album (Dawson 1965). The grass Setaria viridis only reduced beet yield by 26% at a
density of 1 weed per beet compared with a 70% yield loss ﬁom A. retroﬂexus at the
same density (Brimhall et al. 1965, Schweizer and Dexter 1987).

Cgmxtitive Weed Densities

Sugarbeet yield is adversely affected as weed density increases (W eatherspoon
and Schweizer 1971, Schweizer 1981). At lower populations, weed density may
inﬂuence the competitive effect of weeds signiﬁcantly. Because of infra-speciﬁc
competition, heavy weed populations have a saturating competitive effect. When
infestations are severe a several fold difference in the population of weeds will inﬂuence
the total effect very little (Dawson 1970).

Weeds have the ability to be competitive with sugarbeet at low densities. It is
estimated that even if one to ﬁve percent of weeds escape, yield may be reduced by six to
12% (Schweizer and Dexter 1987). A mixed population of various weed species at the
density of six plants per 30 meters of row reduced sugarbeet yield 11 to 14% (Schweizer
1981, Schweizer and Bridge 1982). Eight A. retroﬂexus plants per 30 meters of row

reduced sugarbeet yield 16% (Brimhall er al. 1965, Schweizer and Dexter 1987). Other

13

broadleaf weeds such as K. scoparia reduced sugarbeet yield at densities as low as one
weed per 25 foot of row (Weatherspoon and Schweizer 1971). K. scoparia can compete
with sugarbeet plants within a 48 inch radius (Weatherspoon and Schweizer 1971). C.
album at a density of four to six plants per 30 meters of row reduced sugarbeet yield by
eight to 12% (Schweizer 1983). In general, a grower will experience a decrease in
sugarbeet yield from three to six broadleaf weeds per 30 meters of row (Schweizer 1981).
In contrast, grasses such as S. viridis are competitive only at densities greater than one
weed per sugarbeet (Brimhall et al. 1965).

wi ' r w

Competition ﬁ'om weeds begins ﬁrst within the row (Dawson 1965). Weeds
emerging within the row compete directly with the crop for resources. It can be argued
that the only weeds that matter are those which emerge within a four inch band over the
row. This is because the space within the row is shaded quickly by the crop and weeds
between the rows can be easily removed with cultivation (Dawson 1970). The
competitive effects of weeds may extend 32 inches in most cases (Weatherspoon and
Schweizer 1971). The yield of sugarbeet in cultivated plots where weed densities were
only in a ten inch band over the row, was not impacted as greatly as in uncultivated plots

(Zirndahl and Fertig 1967).
Program approach to weed control in sugarbeet

Weed control in sugarbeet often relies on preemergence herbicides at planting
followed with one or more postemergence herbicide applications. In Michigan the use of
preemergence herbicides is common. This is also true for areas such as Nebraska and

Wyoming where over 50% of the sugarbeet is treated with a residual, soil-applied

l4

herbicide (Renner 1999; personal communication). Sugarbeet growers in North Dakota
and Minnesota use few soil applied, residual herbicides. In 1998 only 11% of these
growers used soil-applied herbicides (Dexter and Luecke 1999).

Preemergence herbicides are biologically active in the soil, controlling newly
emerging weed seedlings. The pre-mixture of the postemergence herbicides
phenmedipham (3 [(methoxy carbonyl) amino] phenyl (3-methyl phenyl) carbamate) and
desmedipham (ethyl [3-[[(phenylamino) carbonyl]oxy]phenol]carbamate) controlled
weeds more effectively when applied to areas previously treated with the preemergence
herbicide cycloate (5-ethyl cyclohexylethylcarbamothioate) (Dexter 1994). The greatest
reduction in broadleaf weed density occurred in the preemergence followed by
postemergence herbicide treatments (Wilson 1992). The number of postemergence
treatments and the need to include a preemergence herbicide to achieve the most cost-
effective weed control varies according to weed density (Miller et al. 1997). The greatest
gross return in S/ha was when preemergence and postemergence herbicides were both
applied. Preemergence followed by postemergence herbicides have proven to be
effective in providing season long weed control (Schweizer 1980, Winter and Weise
1982, Wicks and Wilson 1983, Miller and Fomstrom 1988, Miller and Fomstrom 1989,
Miller et al. 1992).

The high cost of traditional sugarbeet herbicides such as desmedipham, pyrazon
(5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone), and ethofumesate (2-ethoxy-2,3-
dihydrox-3,3-dimethyl-5-benzofuranyl methane sulfonate) has led many growers to apply
these products in a way that reduces the amount of active ingredient applied per hectare.

These herbicides are applied in a band over the row of the crop, thus controlling weeds

15

within this band (Schweizer and Dexter 1987). Cultivation between the rows controls the
remaining weeds. Sugarbeet producers presently use a combination of chemical,

mechanical, and manual weed control methods (Miller et al. 1992).
Weed emergence and cultivation

Cultivation between the rows of the crop is a common technique for weed control
in sugarbeet. With the introduction of sugarbeet varieties that are resistant to herbicides
such as glufosinate or glyphosate, cultivation as a weed control strategy will no longer be
required. This is because these herbicides can be economically applied broadcast and
provide excellent weed control. In spite of this new technology, growers have expressed
an interest in continuing to cultivate sugarbeet. Many growers employ a “cutaway”
cultivation early in the season to aerate and loosen the soil, facilitating the establishment
of young sugarbeet plants. In addition to weed control, cultivation may be used to loosen
the soil, apply nitrogen fertilizer, place soil around the sugarbeet plants to aid in harvest,
and enhance the aesthetics of the crop in the ﬁeld.

One argument against using cultivation with herbicide resistant crops is that
tilling the soil may increase the emergence of new weed seedlings (Egley and Williams
1990). Glufosinate and glyphosate have no residual soil activity and only control
emerged weeds (WSSA 1994). New weed emergence after herbicide application could
translate into decreased control. Seed germination and dormancy is complicated and can
be inﬂuenced by many factors including soil temperature, soil moisture, and exposure to
light (Baskin and Baskin 1990, Alrn et al. 1993, Salisbury and Ross 1992, Taiz and

Zeiger 1998). Cultivation can affect the distribution of seeds or the environment needed

for germination (Egley 1986, Egley and Williams 1990). These affects can be both
positive and negative to weed emergence.

One way in which tillage may inﬂuence seedling emergence is by affecting soil
temperature and moisture. Research has shown a relationship between weed growth and
soil temperature and soil moisture (Wiese and Binning 1987). A reduction in tillage can
reduce soil temperature and increase soil moisture (Oryokot et al. 1997c). Reducing
tillage concentrates weed seeds near the soil surface (Clements et al. 1996). As
temperature increases above a minimum threshold, the rate of seed germination and shoot
elongation is increased. For some species there is a temperature above which
germination and elongation decrease (Oryokot et al. 1997b & 1997c). Temperature and
moisture are also known to regulate secondary dormancy of some annual weed seeds.
Low soil temperature may break seed dormancy, while high temperatures induce
dormancy (F orcella et al. 1997). The actual effect tillage has on soil moisture, soil
temperature, and weed seed germination can be somewhat limited. As an example, A.
retroﬂexus seedlings are physiologically restricted to germination depths of less then 2.5
cm. At shallow soil depths heat and moisture transfer between soil and atmosphere is
rapid, reducing the affect of tillage on seed germination. This phenomenon varies by soil
type or sites with different cropping histories (Oryokot et al. 1997a). These criteria may
also limit the effect of tillage on annual grasses such as S. faberi, which has the greatest
emergence from a soil depth of less then a centimeter (Fausey and Renner 1997).

Exposure to light is another variable affected by tillage (Wesson and Wareing
1969, Buhler 1997, Gallagher and Cardina 1998). Exposure to light can break seed

dormancy in some plant species. This requirement for light would keep propagules that

17

are buried more than a few centimeters from germinating, which is an advantage for plant
species with small seeds (Salibury and Ross 1992, Buhler 1997). The response of seeds
to light is mediated by phytochrome, which exists in two forms. Phytochrome red (Pr),
the inactive form, is converted by exposure to red light to phytochrome far red (Pfr)
(Ascard 1994). Phytochrome in the buried seeds is in the Pr form and is converted to Pfr
upon exposure to sunlight, resulting in a series of physiological events that lead to
germination (Gallagher and Cardina 1998, Taiz and Zeiger 1998). In research by Buhler

(1997), emergence of small-seeded weeds such as C. album and Polygonum

r—n

pennsylvanicum decreased when tillage was performed in the dark. Similar results were
reported by Ascard (1994), in which the gemiination of some weed species was reduced
when tillage implements excluded light. Unlike Buhler’s, Ascard’s experiments did not

show a decrease in C. album germination when tillage was performed at night. Gallagher

 

and Cardina (1998) reported a decrease in emergence of some weed species when tillage
was performed at night versus during the day; however, variability of this result does not
make night tillage a viable approach for reducing the number of emerging weeds.
Though the microclimate variable that accounted for the most variation in the emergence
of C. album was temperature, exposure to light prolonged non-dormancy (F orcella et al.
1997). This interaction between temperature, light requirement, and moisture on weed
seed germination is complex and varies by weed species.

The effect of cultivation on weed emergence may vary according to the time of
year. When soil is cultivated there is a small proportion of the total seed bank which is
released from dormancy (Roberts 1984). Weeds such as C. album tend to appear more

frequently aﬁer spring tillage and continue to appear whenever the soil is disturbed.

l8

 

Temperature largely determines this seasonal pattern of emergence, however soil

moisture also seems to have an overriding affect.
Will Herbicide Resistant Crops Lead to Resistant Weeds?

For thousands of years people have tried to manipulate plants for their own use.
At ﬁrst this was simply through the harvest and eventually the domestication of wild
plants into cultivated crops. Technology has ushered in a new era in agriculture;
Through the use of crop breeding, machinery, mineral fertilizers, and pesticides, world
crop production continues to increase. One of the most recent advancements is the use of
biotechnology to create genetically transformed crops. An example of one such crop is
canola, which now exists with transgenic resistance to several herbicides, increased
methionine in the seed meal, male sterility, heavy metal tolerance, and insect resistance
(Brown and Brown 1996). Even with all of the improvements that can be made,
herbicide resistance is the most common genetically engineered trait (Brown and Brown
1996). There are several reasons for the development of herbicide resistant crops,
including increased options for the grower and the use of “environmentally safer”
herbicides. Some however, argue that the use of biotechnology could result in
detrimental effects to the environment. That argument in itself is a broad topic that may
never be resolved, but for the weed scientist thought should be given as to whether
herbicide resistant crops could facilitate the occurrence of herbicide resistant weeds. At
this point it is uncertain if cr0ps that are resistant to herbicides will decease the incidence
of herbicide resistance in weeds or enhance it (Radosevich et al. 1992).

Herbicide resistance in weeds could develop if the increased use of a single

product allows for the selection of naturally resistant plants, the crop itself becomes a

19

weed, or through cross fertilization of crops with weedy species. It is common to
experience a weed shift with different management methods, allowing tolerant species to
dominate in a given area. The proper use of resistant crops should not increase this
problem (Burnside 1992). Similarly, natural selection for resistance would be the result
of abusing technology. Knowing that misuse of a herbicide resistant crop could result in
natural selection for resistance or shifts in weed populations, concern now falls to the
uncertainty of a resistance gene being inadvertently released into the environment.

It is conceivable that the crop itself could become a weed, and with it a genome
expressing the trait for herbicide resistance would be released uncontrolled into the
environment. There are examples of plant species that exist as both crops and weeds,
including shattercane and wild proso millet. In both of these cases seed dormancy
allowed evolution to a “weedy” plant, and would have happened whether these species
displayed herbicide resistance or not (Burnside 1992). Another example would be wild
oats, differing from cultivated oats by only one gene that determines seed shedding at
maturity and hair on the seeds (Darrnency 1994). Still, it is unlikely that the crop itself
will become a problem weed. Crops are genetically uniform compared to wild relatives,
and selection would have little opportunity to operate on an individual escaped plant. In
addition, crops lack the longevity in the amount of time the seed is viable. If crops were
to display seed dormancy, dispersal through time would be a concern (Linder and Schmitt
1994)

It is clear that crops and weeds can spontaneously hybridize in the ﬁeld, and this
ﬂow of genes from genetically engineered crops into wild plant relatives could result in

the escape of transgenes (Arriola and Ellstrand 1996). Examples of hybridization

20

between crop and weed include sorghum crossing with wild sorghum to give rise to
johnsongrass, and sugarbeet crossing with a wild beet to yield weed beets (Brown and
Brown 1996). Recently a botanist found a variety of green foxtail that was actually a
cross of the crop foxtail millet and green foxtail (Darmency 1994). Outcrossing may not
only be a problem between related species. Existing literature describes intergeneric
cross compatibility within the family Brassicaceae (Brown and Brown 1996). This
family includes canola, wild mustard, shepherdspurse, and ﬁeld pennycress. Concern
about hybridization between weed and crop is justiﬁed, since as much as wild forms can
be repositories for genetic information they can also be sinks for genes ﬂowing from the
crop (Arriola and Ellstrand 1996).

One well-documented example of crop-weed cross compatibility is that of the
weed beet in Europe. Considerable genetic variability can exist in sugarbeet. The major
difference in weed beets and cultivated beets is the life cycle. A cultivated beet, like
those grown in Michigan is a biennial plant, while beets with weedy characteristics are
annuals. This life cycle depends on the presence or absence of the vemalization
requirement. Natural selection for an annual life cycle, early ﬂowering and seed
maturation, and seed shattering allows weed beets to reproduce in cultivated ﬁelds. The
weed beet is likely a result of wild beets pollinating the seed production of cultivated
beets (Boudry et al. 1993). Since all of these are considered the same species and are
inter-fertile, great care should be taken around seed production areas. Furthermore,
cultivated beets should not be allowed to set seed, meaning growers need to destroy any

bolting plants in their ﬁelds (Boudry et al. 1993).

21

Though there are several other good examples of gene ﬂow out of crops into wild
relatives, the future of herbicide resistant crops may not be bleak. In reality the chances
of a gene escaping from most crops is very small. There are few crops that are
compatible to interbreed with wild relatives in such a manner as previously described.
Even if a wild plant is capable of crossing with a crop species, high selection pressure is
necessary to exclude competition from each species own pollen (Gressel and Kleifeld
1994). Furthermore, pollination does not mean that hybridization will be successful.
Hybrid infertility is a problem for many interspeciﬁc crosses, and the frequency of such
hybrids that backcross with the wild parents would be low (Darmency 1994). Under
greenhouse conditions only about 1 in 25 crosses of ﬁeld mustard to canola produced
seeds. Of those only 2% were fertile, due to cytological defects and lack of chromosome
pairing (Brown and Brown 1996). In the ﬁeld so few viable seeds would pose little risk
of gene ﬂow. One more problem that exists preventing the formation of weed-crop
hybrids is that crops and wild relatives may not ﬂower at the same time. In this situation
there is said to be a hybridization barrier. With canola and wild mustard there was 7
times more pollen and 18 times more wild stigrnas, if a late ﬂowering cultivar is planted
instead of an early ﬂowering cultivar. A similar trend is seen between foxtail millet and
green foxtail, where a late maturing crop cultivar translated into a 30-fold increase in
hybridization (Darmency 1994). Manipulating the time of crOp pollination may help
reduce the potential for loss of genes, but may adversely affect grain yield.

Historically, hybridization between crops and weeds was of little concern.
Desirable traits in crops are often detrimental to weeds, resulting in hybrids that are poor

competitors in native habitats (Arriola and Ellstrand 1996). The ability of a plant to

22

become a weed is only possible if it has an adaptive or competitive advantage. A
transgene for herbicide resistance confers higher ﬁtness in a herbicide treated area, but is
not beneﬁcial in wild areas (Darmency 1994). It is unlikely that a plant acquiring a
herbicide resistance gene will become a weed, since this trait by itself is basically neutral.
Wild species will remain “weedy” only until more aggressive plants begin competition or
until other herbicides are used (Gressel and Kleifeld 1994). Herbicide resistance by itself
can not make a wild plant be a persistent pest.

When assessing the risk of transgene escape several steps should be followed.
First, what is the potential for interspeciﬁc compatibility of the genomes of crops and
wild plants in the area? Second, how will the gene behave in wild populations
(Darmency 1994)? Basically if there are no wild relatives capable of crossing with a crop
there is virtually no risk of transgene escape. Even if hybridization is possible, unless the
hybrid that is formed is apometic the genetic material has to be preserved through
backcrossing with wild relatives.

The last consideration may be the most complicated. That is, will an escaped
gene impact the environment? Keep in mind that there will be an increase in plant
population only if the most limiting factor is manipulated (Radosevevich et al. 1992).

So, it is important to know a plant species’ limiting factor in order to evaluate potential
environmental impact. If a transgene has the ability to alter some limiting factor for wild
plants, release of the gene is more of a concern.

There are several traits that have been transformed into crop plants in recent years.
These improved crops will undoubtedly change agriculture, and improve the lives of

many people. Though the risks of developing herbicide resistant crops are minor

23

compared with the potential beneﬁts, there is still concern existing over the possible
escape of these genes into the environment. This idea is justiﬁed, and environmental
impact of escaped genes should be assessed. The evolution of new herbicide resistant
weeds, or the crop itself becoming a weed is possible, but unlikely if breeders, molecular
biologists, agronomists, and weed scientists respect the new technology that is available

to them.

24

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26

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28

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29

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30

Chapter 2

Competitiveness of Annual Weeds in
Herbicide Resistant Sugarbeet

Abstract

With the recent introduction of sugarbeet modiﬁed to express resistance to
glyphosate or to glufosinate, growers will have a new Option for weed control. Unlike
conventional sugarbeet herbicides, glyphosate or glufosinate can control weeds that
exceed 5 cm in height. Research was conducted in 1998 and 1999 to determine when
weeds became competitive in herbicide resistant sugarbeet. The research consisted of six
trials located at three sites in both 1998 and 1999. Glyphosate was applied POST at 0.63
kg ae/ha to weeds less then 10 cm in height and at 0.84 kg ae/ha to weeds greater then 10
cm in height. Similarly, glufosinate was applied POST at 0.29 or 0.40 kg ai/ha to weeds
less then 10 cm in height and 0.40 kg/ha to weeds greater then 10 cm in height. The
dominant weed species at each site were Amaranthus retroﬂexus and Chenopodium
album. To evaluate when weeds become competitive herbicide was applied to the
appropriate sugarbeet cultivar when weeds attained an average of 2.5, 5, 10, 20, or 30 cm
in height. Plots were then maintained weed-free for the duration of the growing season
by additional herbicide applications. To evaluate the length of time weed control must be
maintained in sugarbeet, either herbicide was applied to 2.5 cm weeds and then weed-free
conditions were maintained until the crop reached the four to ﬁve leaf pair growth stage,
or for two, four, or six weeks after this growth stage. Sugarbeet yield and weed control

data was then used to establish a critical weed control period in sugarbeet.

31

Sugarbeet yield was not reduced in 1998 or 1999 by weeds that emerged with
sugarbeet and grew to 10 cm or greater in height prior to herbicide application, when
compared with a weed-free control. This suggests that weed removal did not need to
commence until ﬁve weeks after planting. In 1998 sugarbeet yield decreased when
weed-free conditions were maintained only until the crop reached the fourth to ﬁfth leaf
pair stage, ﬁve weeks after planting. In contrast, weeds emerging after the fourth to ﬁfth
leaf pair stage of the crop, ﬁve to six weeks after planting did not reduce yield in 1999.

The critical period for weed control in sugarbeet was ﬁve to seven weeks after planting.
Introduction

In 1965 weed competition caused an estimated 8% loss in the potential value of
the sugarbeet crop in the United States (Schweizer 1981). From 1975-1979 weeds caused
an estimated 10% yield loss in sugarbeet which resulted in an approximately $89 million
loss (Schweizer and Dexter 1987). Current estimates of economic loss in sugarbeet from
weeds totaled $60 million even when best management practices were implemented
(Morishita and Downard 1995).

Sugarbeet root yield is reduced when low weed densities are allowed to remain in
the crop for the duration of the season (Table 1). Weed competition decreased sugarbeet
yield by affecting the diameter of the root, but did not affect root length (Brimhall et al.
1965). Decreased root yield resulted in the loss of recoverable sucrose per hectare, but
had no affect on percent sucrose or purity of brei (Brimhall et al. 1965, Zimdahl and
Fertig 1967, Schweizer and Bridge 1982).

Weeds compete with crops for nutrients, water, and light (Kropff 1988, Schweizer

and May 1993). If water and nutrients are plentiful competition for light is the main

32

factor in sugarbeet yield loss due to weeds (Brimhall et al. 1965, Dawson 1965,
Schweizer and Bridge 1982). Weeds may also become problematic in sugarbeet by
contributing to increased crop disease and interfering with pesticide application or
harvest.

Weeds can compete with sugarbeet for a period of time before yield loss occurs.
The period of weed competition that a crop can tolerate is inﬂuenced by weed species,
weed density, relative time of weed emergence, crop vigor, and the availability of
resources (Zirndahl and Fertig 1967, Dawson 1970, Schweizer 1981, Wicks and Wilson
1983, Kropff 1988). Weeds that emerge early in relation to crop emergence have the
most potential to cause yield loss (Dawson 1965, Weatherspoon and Schweizer 1969,
Wicks and Wilson 1983, Kropff 1988). Weeds are most competitive if they emerge
within eight weeks after planting (Wicks and Wilson 1983, Wilson 1992) or within four
weeks after the crop reaches two-leaf stage (Wicks and Wilson 1983, Schweizer and
Dexter 1987, Schweizer and May 1993). Studies by Dawson (1965) showed that
maximum yield was achieved when weed-free conditions were maintained for eight to 12
weeks after planting, or ﬁve to nine weeks after crop emergence. When light was the
only limiting resource the sugarbeet crop tolerated weeds for four to eight weeks after
emergence (Brimhall et al.1965, Scott et al. 1979, Schweizer and May 1993). The ability
of sugarbeet to compete with late emerging weeds is diminished if the crop is not at
normal vigor or full stand (Dawson 1974, Schweizer and Dexter 1987).

The critical period is the time during which the presence of weeds reduces crop
yield (Figure 1). Weed control methods should be employed before yield loss occurs,

and then should continue until the crop can compete with newly emerging weeds.

33

Literature suggests that the critical period for sugarbeet is approximately four weeks in
length, when the crop is ﬁom the four to the 12-leaf stage in development (Dawson 1974,
Scott et al.. 1979, Van Heemst 1985, Schweizer and May 1993).

In traditional sugarbeet production systems, timing of weed control is restricted
by postemergence herbicides which control weeds less then 2.5 cm in height, and the
availability of hand-labor (Schweizer and May 1993, Thorsness et al. 1999). With the
recent introduction of sugarbeet modiﬁed to express resistance to glyphosate or to
glufosinate, growers will have the ability to effectively remove weeds that are 8 cm or
greater in height (Dexter et al. 1999, Guza et al. 1999, Thorsness et al. 1999). Excellent
control of annual weeds is obtained with two to three sequential applications of
glyphosate or glufosinate starting when sugarbeet is in the two or four leaf stage (Mesbah
and Miller 1999). The ability to control large weeds and provide consistent results will
allow these herbicides to be applied at multiple times to optimize weed control and
sugarbeet yield. The purpose of this research was to employ the advantages associated
with herbicide resistant sugarbeet to determine when weeds were competitive in
sugarbeet. This information could then be used to plan an effective weed management
program in herbicide resistant sugarbeet.

Materials and Methods

Research was conducted at three sites in Michigan in 1998 and 1999 in
cooperation with Michigan and Monitor Sugar Companies (Table 2). Each of the
locations consisted of one glyphosate resistant sugarbeet study and one glufosinate
resistant sugarbeet study. The ﬁrst site was established at the Michigan State University

Saginaw Valley Bean and Beet Research Farm in Saginaw County. Michigan Sugar’s

34

sites were located in a grower’s ﬁelds in Saginaw County, while Monitor Sugar’s sites
were located in Bay County. Each study at each site was arranged as a randomized
complete block design with four replications. The sugarbeet varieties used in all studies
were Betaseed ‘891LL’ and Hillshog Monotty ‘RH3RR’.

In both 1998 and 1999 glyphosate was applied at 0.63 kg ae/ha when weeds were
less then 10 cm in height, and 0.84 kg/ha when weeds were 10 cm or greater in height at
the time of the ﬁrst herbicide application. In 1998 glufosinate was applied at 0.29 kg
ai/ha to weeds less then 10 cm in height, and 0.40 kg/ha when weeds were 10 cm or
greater in height. Glufosinate was applied to all treatments at 0.40 kg/ha in 1999 because
of inconsistent weed control from 0.29 kg/ha in 1998, and to recognize recommended
rates. Ammonium sulfate at 2.8 kg/ha was included in each herbicide application.

Herbicides were applied postemergence to the respective transgenic sugarbeet
varieties with a tractor-mounted compressed air sprayer, when weeds were 2.5, 5, 10, 20,
or 30 cm in height (Table 3). Plots were then hand-weeded when necessary four to seven
days after herbicide application, and kept weed-free with glyphosate and glufosinate for
the remainder of the growing season. These treatments determined the length of time that
sugarbeet could tolerate weeds. In other plots glyphosate and glufosinate were applied
when weeds reached 2.5 cm in height, and treatments were maintained weed-free with
the use of additional herbicide applications until the crop reached either the four or ﬁve
leaf pair (8 or 10 leaf) stage (Table 3). The total amount of glyphosate and glufosinate
applied in any treatment did not exceed the maximum seasonal rates proposed on the
herbicide label of 3.36 and 1.2 kg/ha respectively (J. Kauffrnan, Monsanto, personal

communication, August 1998 and K. Thorsness, AgroEvo, personal communication,

35

February 1999). After these time periods weeds were allowed to infest the sugarbeet.
Together these treatments determined the crop stage at which weeds no longer needed to
be controlled. These weed-free periods determined the critical period for weed control in
sugarbeet. Two additional treatments were also included to evaluate the effect of two
versus three applications of glyphosate or glufosinate during the same four-week period.

The number of emerged weeds prior to the ﬁrst application of glyphosate and
glufosinate was recorded by counting seedlings in a 20 cm by 69 cm quadrant over the
row (Table 4). A ﬂag was placed in the corner of each quadrant in the untreated control
plots. Weed biomass in each plot was estimated in August by harvesting above ground
weed growth in a 20 cm band placed over the sugarbeet row for the entire length of the
plot with the exception of the untreated control. Visual percent weed control was also
recorded at this time. Weeds were collected from the untreated control in the previously
marked quadrant only. All harvested weed biomass was dried and weights recorded. In
1998 both the Michigan and Monitor Sugar Co. locations were machine harvested for
root yield October 5 through October 9. The third site at the Bean and Beet Research
Farm was not harvested in 1998 due to stand loss from seedling disease. In 1999
sugarbeet was harvested from October 5 through October 15. The glyphosate resistant
sugarbeet at the Monitor location was not harvested because of inadequate stand due to
poor crop emergence. In both years all sugarbeet samples were analyzed for sugar
content and clear juice purity by Michigan Sugar Company (Michigan Sugar, Carrollton,
MI 48724).

All data was subjected to analysis of variance using the general linear means

procedure in SAS (SAS Institute, Cary, NC 27513). Mean separation was performed

36

using Fisher’s Least Signiﬁcant Difference (LSD) at the 0.05 level. An F -max, Hartley’s,
test was performed to determine if sites could be combined (Kirk 1982). Data across
sites could be combined; however, data across years could not be combined due to year
by treatment interactions. Treatments evaluating the length of time weeds could remain
in the crop and the crop stage to which weed-free periods must be maintained were also
subjected to separate analysis of variance. The adjusted means were then graphed. SAS
was used to generate coefﬁcients for orthogonal polynomials for testing the order of
trends associated with these graphs; however not enough data points were present for this
analysis. Regression of weed density, weed biomass in the untreated plots, and sugarbeet

root yield was performed.
Results and Discussion

Much of the Michigan sugarbeet producing region endured drought in 1998 with
many growers experiencing inconsistent crop emergence, slow crop growth, and slow
canopy development. Crop emergence and initial growth in our studies was rapid due to
warm temperatures and good soil moisture at planting at all sites in 1998. Sugarbeet
growth was later slowed due to a lack of precipitation (Table 3). In contrast the 1999
season received adequate rainfall and sugarbeet growth through June and July was rapid.
Initial growth in May was slower in 1999 compared with 1998 due to a short period of
cool weather. The dominant weed species present at all sites in both years were
Amaranthus retroﬂexus and Chenopodium album.

The presence of weeds did not affect the sugar content or purity in any of the
studies. Lower recoverable sucrose was a direct result of lower sugarbeet root yield.

Sugarbeet root yield was lower when weed density or weed biomass is higher.

37

Regression of sugarbeet root yield and weed density was represented by an exponential
curve, which can be linearized with a logarithmic transformation (Figure 2a). When
weed densities are low a linear regression may be used (Cousens 1991 ); however, the
inﬂuence of weed density on yield loss diminishes at higher weed populations due to a
saturating effect (Dawson 1970). The ability to predict yield reductions in sugarbeet
using linear regression diminished when weed densities exceed 24 plants per 30 m of row
at harvest (Schweizer 1981).

Weed density was a better predictor of yield loss than weed biomass (Figures 2a
and 2b). Similar to results by Wicks and Wilson (1983) an increase in weed biomass
accounted for 47% of the variability in sugarbeet yield (Figure 2b).

In 1998 weeds reduced sugarbeet root yield in the untreated plots by more then
70% compared to yield where weeds were removed at 2.5 cm (Figures 3a and 3b).
However, root yield was not reduced in either glyphosate or glufosinate resistant
sugarbeet when weeds were allowed to reach 20 cm in height, six weeks after planting,
prior to herbicide application. Although root yield was not reduced, sugarbeet was
visually stunted and hand-labor was required to remove these 20 cm weeds. Similar
results were reported the same year in North Dakota where crop stunting and yield loss
were observed when weeds were not removed until three to four weeks after the
sugarbeet cotyledon stage (Dexter et al. 1999).

In 1999 root yield was not reduced in either glyphosate or glufosinate resistant
sugarbeet when weeds were allowed to reach 30 cm in height, seven weeks after planting,
prior to herbicide application (Figures 4a and 4b). Sugarbeet yield in untreated plots

reduced by 35% compared with ‘weed removal at 2.5 cm’ plots. Sugarbeet growth in

38

1999 was not visually stunted in any treatment and hand-labor was required only to
remove weeds that exceeded 20 cm in height. Absence of visual stunting in 1999 may
have been due to increased soil moisture and differences in weed densities. Weed
densities at sites harvested in 1999 were 67% lower then in 1998 (Table 4). In non-
irrigated sugarbeet, yield loss due to weed competition can differ from year to year.
Research in New York showed 44% yield loss in 1964 compared with 62% yield loss in
1965 (Zimdahl and Fertig 1967). In studies conducted by Hubbell (1997) in Michigan
from 1992 through 1995 the same density of Amaranthus retroﬂexus reduced sugarbeet
yield ﬁ'om eight to 65% depending on the year.

Sugarbeet yield in 1998 was also reduced in treatments where the crop remained
weed-free until the eighth leaf stage (ﬁve weeks after planting) and then weeds were
allowed to grow (Figures 5a and 5b). Yield was greater where weed control was
extended an additional two weeks, until seven weeks after planting when the crop
reached the 12-leaf stage. Weed biomass was 99% less when weed control was
maintained until seven weeks after planting (12-leaf crop stage).

Sugarbeet yield in 1999 was not reduced when the crop remained weed-free until
the four-leaf crop stage, four weeks after planting, and then weeds were allowed to grow
(Figures 6a and 6b). Weed biomass was 99% less if weed control was maintained for
ﬁve weeks after planting (eight-leaf crop stage).

The beginning of the critical weed control period was arbitrarily set at a time
when no relative yield loss or crop stunting was observed, and weeds could be removed
with glyphosate or glufosinate. We set the end of the critical weed control period at the

time when there was no relative yield loss and weed biomass was reduced by 99%.

39

These studies suggest that under adverse growing conditions (high weed densities and/or
low soil moisture such as in 1998) weed control must begin prior to weeds reaching 10
cm in height, 5 weeks after planting (sugarbeet was at the eight-leaf stage), and then must
be maintained until the crop reaches the 12-leaf stage, 7 weeks after planting (Figures 7a
and 7b). Under favorable growing conditions such as in 1999, weed control must begin
prior to weeds reaching 20 cm in height, 6 weeks after planting, and then must be
maintained until the crop reaches the eight-leaf stage, 5 weeks after planting (Figures 8a
and 8b). It is important to note that all weeds that emerged prior to the 12-leaf crop stage
in 1998 and the eight-leaf crop stage in 1999 were removed with herbicides. This would
include any small weeds that were emerging but not yet visible. Weed-free conditions
extended for a short period beyond the ﬁnal herbicide application.

There was no difference in sugarbeet yields if weeds were initially removed at a
height of 2.5 cm with glyphosate or glufosinate and then retreated 14 and 28 days later
compared to plots retreated only 28 days later (Tables 5 and 6). This suggests that after
the initial herbicide application newly emerging weeds were not competitive for 28 days
after the ﬁrst herbicide application. Therefore subsequent herbicide applications could

have been delayed for four weeks after the ﬁrst herbicide application in our research.

Conclusions
The critical weed control period for sugarbeet was from 5 to 7 weeks after
planting in 1998 and at 5 weeks after planting in 1999. Under favorable growing
conditions and lower weed densities sugarbeet was able to compete with weeds more
effectively. Our studies support previous research that suggested weed control must be

maintained for four to nine weeks after crop emergence (Dawson 1965, Weatherspoon

40

and Schweizer 1969, Wicks and Wilson 1983, Van Heemst 1985, Schweizer and Dexter
1987, Schweizer and May 1993). Herbicide applications should be made so that all
weeds that emerge prior to the end of the critical weed control period are controlled.
Weed control in sugarbeet will require at least two applications of glyphosate or
glufosinate (Figure 9). Studies in 1999 suggested that one properly timed herbicide
application at the eight-leaf crop stage could have maintained sugarbeet yield and quality.
This is optimistic considering the difficulty of achieving weed control with a herbicide
that does not have soil activity, the variability of environmental conditions, and the
numerous factors that can affect sugarbeet stand and crop development.

Conventional sugarbeet herbicides can cause crop injury and must be applied
when weeds are less then 2.5 cm in height. Application of glyphosate or glufosinate to
resistant sugarbeet could injure the crop less, give greater weed control, and ‘save time’
by allowing multiple, cost effective herbicide applications to be made. Since sugarbeet
tolerated the presence of weeds exceeding 10 to 20 cm in height, the ﬁrst herbicide
application was restricted only by the ability to consistently remove the weeds that are
emerged. A grower could make a second application of glyphosate or glufosinate two to
four weeks later to attempt to remove newly emerging weeds. Sugarbeet that is larger
then the eight to lZ-leaf stage would probably grow quickly, providing a canopy that
would restrict the competitive ability of weeds. A third herbicide application could be

made without crop injury or yield loss if weed control was not satisfactory.

41

Literature Cited

Brimhall, P.B., E.W. Chamberland, and HP. Alley. 1965. Competition of annual weeds
and sugarbeets. Weeds 13:33-35.

Couscns, R. 1991. Aspects of the design and interpretation of competition (interference)
experiments. Weed Technol. 5:664-673.

Dawson, J.H. 1965. Competition between irrigated sugar beets and annual weeds. Weeds
13:245-249.

Dawson, J.H. 1970. Time and duration of weed infestations in relation to weed-crop
competition. Proc. Southern Weed Sci. Soc. 23:13-25.

Dawson, J.H. 1974. Full season weed control in sugarbeets. Weed Sci. 22:330-335.

Dexter, A.G., I. Rothe, and J .L. Luecke. 1999. Weed control in Roundup Ready and
Liberty link sugarbeet. Proc. Amer. Soc. Sugar Beet Technol. 30: 131-137.

Guza, C.J., C.V. Ransom, D. Morishita, and C. Mallory-Smith. 1999. Effectiveness of
glyphosate and glufosinate for weed control in transgenic Beta vulgaris varieties. Proc.
Amer. Soc. Sugar Beet Technol. 30:139-140.

Hubbell, L. 1997. Weed test. Proc. Amer. Soc. Sugar Beet Technol. 29:23-25.

Kirk, RE. 1982. Page 78 in Experimental Design. 2“d ed. Brooks/Cole. Monterey, CA.
911p.

Kropff, M.J. 1988. Modelling the effects of weeds on crop production. Weed Res.
28:465-471.

Mesbah, AD. and SD. Miller. 1999. Weed control in Roundup Ready and Liberty Link
sugarbeets. Proc. Amer. Soc. Sugar Beet Technol. 30: 143.

Miller, AB. and H]. Hopen. 1991. Critical weed-control period in seeded cabbage
(Brassica oleracea var. capitata). Weed Technol. 5:852-857.

Morishita, D.W. and R.W. Downard. 1995. Weed control in sugar beets with
triﬂusulfuron as inﬂuenced by herbicide combination, timing, and rate. J. Sugar Beet Res.
32:23-35.

Schweizer, EB. 1981. Broadleaf interference in sugarbeets (Beta vulgaris). Weed Sci.
29:128-133.

42

Schweizer, BE. 1983. Common lambsquarters (Chenopodium album) interference in
sugarbeets (Beta vulgaris). Weed Sci. 31: 5-8.

Schweizer, BE. and L.D. Bridge. 1982. Sunﬂower (Helianthus annuus) and velvetleaf
(Abutilon theophrasti) interference in sugarbeets (Beta vulgaris). Weed Sci. 30:514-519.

Schweizer, BE. and A.G. Dexter. 1987. Weed control in sugarbeets (Beta vulgaris) in
North America. Weed Sci. 32113-133.

Schweizer. BE, and M.J. May. 1993. Pages 484-519 in The Sugar Beet Crop: Science
into Practice. Weeds and Weed Control. Ed. D.A. Cooke and R.K. Scott. Chapman &
Hall. London. UK.

Scott, R.K., D.W. Wilcockson, and FR. Moisey. 1979. The effects of time of weed
removal on growth and yield of sugar beet. J. of Agri. Sci. 93:693-709.

Thorsness, K.B., T.W. Kleven, C.P. Hicks, and DP. Dwyer. 1999. Use of Liberty in
transgenic sugar beet. Proc. Amer. Soc. Sugar Beet Technol. 30:144.

Van Heemst, H.D.J. 1985. The inﬂuence of weed competition on cr0p yield. Agri.
Systems 18:81-93.

Weatherspoon, D.M. and BE. Schweizer. 1969. Competition between kochia and
sugarbeets. Weed Sci. 17:464-467.

Weatherspoon, D.M. and BE. Schweizer. 1971. Competition between sugarbeets and
ﬁve densities of kochia. Weed Sci. 19:125-128.

Wicks, G.H. and R.G. Wilson. 1983. Control of weeds in sugarbeets (Beta vulgaris) with
hand hoeing and herbicides. Weed Sci. 31:493-499.

Wilson, R.G. 1992. Sequential herbicide application for weed control in sugarbeets. J.
Sugar Beet Res. 29:1-7.

Zirndahl, R.L. and SN . Fertig. 1967. Inﬂuence of weed competition on sugarbeets.
Weeds. 152336-339.

43

Table 1 — Minimum weed densities that are reported to be competitive and reduce
sugarbeet root yield and recoverable sucrose.

 

 

Weed Species Weed Density Irrigation Author Year
Amaranthus retroﬂexus 1 per 8 sugarbeet Yes Brimhall 1965
& Setan‘a vin'dis
Kochia scopan’a 4 per 30m row Yes Weatherspoon 1971
8 Schweizer
Amaranthus retroﬂexus 3-6 per 30m row Yes Schweizer 1981
Chenopodium album &
Kochia soopan’a
Chenopodium album 4-6 per 30m row Yes Schweizer 1983
Amaranthus retroﬂexus 12 per 30m row No Hubbell 1997
& Chenopodium album

 

Table 2 - Soil series, type, organic matter, and planting dates for glufosinate and
glyphosate resistant sugarbeet at each location in 1998 and 1999.

 

 

 

Site -------------- Soil ---------------------------- Planting --------------
Location Year Series Type OMa Glufb Glytc Row Plant
Width Spacing
(%) (date) (date) (cm) (cm)
Michigan 1998 Zilwaukee Silty- <3 4/27d 5/11d 71 1 1
State Univ. clay
loam
Michigan 1998 Sloan- Silt >3 4/28 5/6 71 11
Sugar Co. Ceresco loam
Monitor 1998 Londo Loam <3 5/7 5/7 76 15°
Sugar Co.
Michigan 1999 Zilwaukee Silty- >3 4/28 4/28 71 1 5°
State Univ. Mistequay clay
Michigan 1999 Sloan Silt >3 4/30 4/30 71 15°
Sugar Co. loam
Monitor 1999 Londo Loam <3 5/4 5/4d 76 15c
Sugar Co.

 

‘ OM - organic matter

b Gluf — glufosinate resistant sugarbeet
° Glyt — glyphosate resistant sugarbeet
d Trial could not be harvested due to stand loss.

° Trials were thinned from a 6 cm spacing.

45

Table 3 — Growth stage of sugarbeet' and weed height“ at various weeks after planting in
1998 and 1999.

 

 

 

 

 

1998 1999——
weeks after crop weed crop weed
planting growth height growth height
stage (cm) stage (cm)
1 emergence emergence emergence emergence
2 ooty - 2 If 1 coty 1
3 4 If 2.5 2 If 2.5
4 6 If 5 4 If 5
5 8 If 10 6 - 10 If 10
6 10 If 20 8 - 12 If 20
7 12 If 12 - 14 If 30
8 12-14If 14-18If
9 14 If row closure

 

a Average growth of weeds and crop for three sites each year.

46

Table 4 — Number‘ of common lambsquarters, redroot pigweed, and mixed speciesb per
30 m of row in glyphosate or glufosinate resistant sugarbeet for the Michigan State
University, Michigan Sugar Co., and Monitor Sugar Co. sites in 1998 and 1999.

 

 

 

 

 

Glyt° Gluf°

Site Year Colq Rrpw Totalb Colq Rrpw Totalb
Miﬁhgaiﬂsﬁate 1998 11 8 25 1 1 1 1 74
Micgggaitga' 1998 62 184 256 56 262 329
”@3383” 1998 7 23 51 16 56 69
M‘Bhrif-iwiﬂsﬁte 1999 1 1 62 73 29 44 80
“ng333?” 1999 29 7 36 56 16 67
“83.3.1233” v 1 24 5 13 21

 

a Counts are from untreated plots when weeds were an average height of 2.5 cm.

b Total species varied by site and included common lambsquarters, redroot pi gweed,
velvetleaf, Pennsylvania smartweed, eastern black nightshade, and annual grass.

° Glyt — glyphosate, Gluf — glufosinate, Colq — common lambsquarters,
Rrpw — redroot pigweed

47

Table 5 — Glyphosate resistant sugarbeet root and sugar yield in 1998 and 1999,
combined over two locations.

 

 

 

---1998 Yield--- ----1999 Yield—--
Treatments Tonnage Sucrose Tonnage Sucrose
(Mg/ha) (kg/ha)a (Mg/ha) (kg/ha)b
Untreated 13.6 1330 47.0 5700
Remove 2.5 cm weeds and 48.2 4820 67.8 8030
maintain weed-free
Remove 5 cm weeds and 43.4 4310 70.6 8490
maintain weed-free
Remove 10 cm weeds and 45.3 4370 66.2 7900
maintain weed-free
Remove 20 cm weeds and 44.7 4330 70.3 8480
maintain weed-free
Remove 30 cm weeds and - - 65.3 7890
maintain weed-free
Remove 2.5 cm weeds - - 69.1 8280
Maintain weed-free until 4 38.6 3870 68.4 8190
leafpau
Maintain weed-free until 14 53.1 5220 69.2 8300
days after 4 leaf pair
Maintain weed-free until 28 46.1 4590 69.8 8310
days after 4 leaf pair
Maintain weed-free until 42 50.6 5130 - -
days after 4 leaf pair
Remove 2.5 cm weeds then 47.0 4620 67.6 8100
retreat 28 days later
Remove 2.5 cm weeds than 47.2 4690 67.5 8100
retreat 14 and 28 days later
Mean 43.3 4240 66.6 7970
P-value 0.0001 0.0001 0.0001 0.0001
CV % 18.3 20.0 8.5 9.0
LSDo.65 8.2 879 5.6 717

 

a Average sugar concentration was 15.1%

b Average sugar concentration was 17.4%

48

 

1111
con

Table 6 — Glufosinate resistant sugarbeet root and sugar yield in 1998 and 1999,
combined over two and three locations respectively.

 

 

 

---1998 Yield--- ----1999 Yield—m-
Treatments Tonnage Sucrose Tonnage Sucrose
(Mg/ha) (kg/ha)a (Mg/ha) (kg/ha)b
Untreated 10.9 1 320 42.6 5100
Remove 2.5 cm weeds and 46.6 5430 58.3 6310
maintain weed-free
Remove 5 cm weeds and 46.3 5510 63.7 7120
maintain weed-free
Remove 10 cm weeds and 47.3 5620 60.7 6790
maintain weed-free
Remove 20 cm weeds and 46.7 5610 60.2 6780
maintain weed-free
Remove 30 cm weeds and - - 59.2 6600
maintain weed-free
Remove 2.5 cm weeds - - 57.7 6050
Maintain weed-free until 4 36.5 4800 61.6 6820
leaf pair
Maintain weed-free until 14 45.7 5570 61.4 6670
days after 4 leaf pair
Maintain weed-free until 28 45.7 5570 59.6 6540
days after 4 leaf pair
Maintain weed-free until 42 46.8 5800 - -
days after 4 leaf pair
Remove 2.5 cm weeds then 45.8 5300 59.8 6690
retreat 28 days later
Remove 2.5 cm weeds then 45.0 5140 62.4 6750
retreat 14 and 28 days later
Mean 41.8 4950 59.1 6519.8
P-value 0.0001 0.0001 0.0001 0.0001
CV % 15 15.6 9.5 9.6
LSD 6.7 828 4.6 508

 

° Average sugar concentration was 16.9%

b Average sugar concentration was 18.2%

Figure 1 — Illustration of an average critical weed control period for sugarbeet (sources:
Dawson 1965, Weatherspoon and Schweizer 1969, Wicks and Wilson 1983, Van Heemst
1985, Schweizer and May 1993).

Relative Yield (%)

700

80-
70.
60-
50-
404
30.
204
70-

 

 

Weed-free Period

 

All weeds that emerge
< prior to this point
must be controlled.

 

 

 

 

 

 

 

  

 
 

\ Weedy Period
~

~---—-

Critical Weed
Control Period

 

 

I I I I I I

0 2 4 6 8 10 12 14 16 18 20 22

Weeks After Emergence

50

Figure 2 - Inﬂuence of a) weed density and b) weed biomass on the root yield of
sugarbeet from nine studies in 1998 and 1999.

a)

S”
o
l
l

y = -0.0021x + 4.66
R2 = 0.76

    

2"
(’1
1 AA
.
~
0

Root Yield (log 10)
co A
'01 o

 

O
n—nj—
‘—
-—

 

O
N
O
O
.5
O
O
C)
O
O

Weed Density (plants/3O m row)
b)

60000
50000
°’ 40000
30000-—
20000-—
10000-

0 I I I I I ﬂ

0 5000 10000 15000 20000 25000 30000
Weed Biomass (kg/ha)

      
 

k Iha)

y = -1.396x + 39300
R2 = 0.47

I I

I

Root Yield (

 

51

Figure 3 — Root yields for a) glyphosate resistant sugarbeet averaged over two sites, and
b) glufosinate resistant sugarbeet averaged over two sites, where weeds were removed at
various heights and weed-free conditions were then maintained by the herbicide in 1998.

a) 70 . Sugarbeet Growth Stage
1 l |

60- 4lf 61f 8lf 10lf

 

A A A

‘5 8

30-

Root Yield (Mg/ha)

20"

10-

 

 

2.5 5 10 20 untrt
Weed Height at Initial Application (cm)

U.
V

70'

60‘

40'
30"

20'

Root Yield (Mg/ha)

10‘

 

               

2.5 5 10 20 untrt
Weed Height at Initial Application (cm)

52

Figure 4 — Root yields for a) glyphosate resistant sugarbeet averaged over two sites, and
b) glufosinate resistant sugarbeet averaged over three sites, where weeds were removed at
various heights and weed-free conditions were maintained by the herbicide in 1999.

Sugarbeet Growth Stage

I l I I I
21f 41f 81f 101f 1411'

 

 

 

 

 

 

A A
a)... . , .

A 60 -
0
£
a) 50 " B
E
2 4o -
.2
t 30 -
o
g 20 J

10 -

0 " I I
2.5 5 10 20 30 untrt
Weed Height at Initail Application (cm)
)7, .
A

60 _ 8 AB AB AB
’2
3, 50 -
g c
2 40 "
.9
>- 30 -
‘6
,2 20 -

10 -

0 ‘ I I 1 I ﬁi
2.5 5 10 20 30 untrt

Weed Height at Initial Application (cm)

53

Figure 5 — Root yield of a) glyphosate and b) glufosinate resistant sugarbeet and weed
biomass in 1998 where weed control was maintained for progressively longer periods
after crop emergence (root yield and weed biomass are not comparable).

 

   
 

 

 

 

Sugarbeet Growth Stage
a 00
) 1 I 1 1 'r 25°
70 411 8If 1211 1411
-60 .. 7.0000 i?
a A E:
$50 . °‘ ’ 5000 i
g ‘\‘ 1- ‘ 8
2 40 " ‘t‘ g
g 30 - *Sugarbeet Yield _ (0000 2
'9' - -- Weed Biomass g
20 1
a: 8
1 _ "" 5000 g
10 - ‘. 99% reduction
0 1 4 ' ' ‘ ‘4‘ ' hh__'_____'__‘l 0
0 2 4 6 8 10

Weed-Free Period (weeks after planting)

    

 

 

 

70 -
00° "‘
ﬁ 60 T 'b 20 g
5 50 3’
u ‘ v
E 2. «500° n
2 40 11‘ g
.2 ~- 0
>- 30 - *SugarbeetYIeld 4 1000 a
'5 - -- Weed Biomass 13
a 20 - 00 o
‘ ‘ ‘ ‘ B 11‘ 50 S
10 4 c " ~ . . 99% reduction
0 I I y ‘ ‘ L-—1-——-I-—r-—ﬂ- 0
0 2 4 6 8 10

Weed-Free Period (weeks after planting)

54

Figure 6 - Root yield of a) glyphOsate and b) glufosinate resistant sugarbeet and weed
biomass in 1999 where weed control was maintained for progressively longer periods
after crop emergence (root yield and weed biomass are not comparable).

 

 

 

 

 

 

 

 

 

Sugarbeet Growth Stage
a 1 1 1
) 411 811‘ 12 If -- 7.5000
7° ‘ T ‘1’ =4 A 00
16 6° ‘ " 20° 3
.1: or
3 50‘. 500° 5
g -°-Sugarbeet Yield -- 1 g
:3 40 .. - 0- Weed Biomass g
E 30 . 10000 .2
.6 1n
1:
E 20 ' A __ 5060 8
1o ........ 99% reduction 3
........ B I
o . . ' 2' ‘ 2 u . = . 0
0 2 4 6 8
Weed-Free Period (weeks after planting)
b) __ 25000
70 r
_ - c 0000 A
’1? 60 A A A A 2 g
£ . a
95° “150°“ 7;
5 40 ' B —°—Sugarbeet Yield 8
$2; 30 _ - - -Weed Biomass . 10000 E
.6 m
. A '5
a 20 ll. __ 5000 3
10 ‘ . B 99% reduction 3
0 I . . .E. . - - 7: l = I 0
0 2 4 6 8

Weed-Free Period (weeks after planting)

55

Figure 7 — Critical weed control period for a) glyphosate and b) glufosinate resistant

 

 

 

 

 

 

 

   

  
 

 

  

 

 

 

 

 

56

sugarbeet in 1998.
a) Wee ri weed-free Period
0 Root Yield I Root Yield 0
70 .. A Recoverable Sugar x Recoverable Sugar «L 700
6O . 8-leaf 12-Ieaf _ 6000 g
4; stage stage r D)
; Weed-free Period 00 :5
650 - . l ‘ -- 5° 2
a Weedy Perlod . ,,,,, " 00 5:
240 ‘l “““““““““““ " A0 0:)
o ~~~~~~~~~ 2
5.. 30 . ““““““““ J- 3000 Q
*5 ~~~~~~ E
o o
(It, 20 - Begin weed All weeds that " 7'00 3
removal prior —-> s—-emerge prior to this 0 0
10 to this point. point must be - . 100 &
controlled.
0 I r I I I I o
0 2 4 6 8 10 1 2
Weeks After Planting
b) Wﬁdy Peg’od w - Peri
0 Root Yleld I Root Yield
70 ‘ A Recoverable Sugar x Recoverable Sugar . _ 8000 A
4 8-leaf 12-leaf .. 1000 5
“a stage stage .5:
5 . Weed-free Period .. _ 600° :-
§50 Weedy Period . ------- . ------------- I - i a“ G
V ‘‘‘‘‘‘‘‘ "' " 5000 g,
1:40 i to
:2 1 . 4,000 g
>' 30 - ~~~~~ .n
‘5 ~~~~~~ . . 3000 g
0
a: 20 I Begin weed All weeds that emerge . . 2000 (>3
removal prior ___, 4— prior to this point must 3
1 O to this point be controlled. . _ (000 m
0 I I I I I 1 o
0 2 4 6 8 10 1 2
Weeks After Planting

Figure 8 - Critical weed control period for a) glyphosate and b) glufosinate resistant
sugarbeet in 1999.

 

 

 
   

 

 

 

 

 

 

   

 

  

 

 

 

 

a) Weedy Period Weed-free Period
0 Root Yield I Root Yield
95 " A Recoverable Sugatr}leaf x Recoverable Sugar .L «(000
85 . stage .. «0000
E 000
B 75 i . c 9
E ““““ k ’Weed-free Perl 8000
1, 65 1 “1 ............... ‘I
E ................ .. 1000
>. _. -----
.. 55 - - 6000
8 All weeds that emerge Begin weed
m 45 ' prior to this point must—P <— removal prior 4.. 5000
be controlled. to this point.
35 4 IL 4000
25 . t . . 300°
0 2 4 6 8 1 O 1 2
Weeks After Planting
19) 0666121261190 Weed-.I‘Leeﬂen'm
o Root Yield - Root Yield 107 50
95 . , Recoverable Sugar x Recoverable Sugar 7'
85 8-leaf . . 97 50
A " stage
a .. 3150
e 75 .
g 4- 7750
I; 65 . Weed-Free Period 50
E Weedy Period ------------- we: __________ . ,. 61
>' 55 " .................... d _ 5150
0
g 45 i All weeds that Begin weed -- 4750
emerge prior to this -> 4— removal prior 0
35 point must be to this point. .4. 375
controlled.
25 l7 I I I I I 2150
O 2 4 6 8 1 0 1 2
Weeks After Planting

57

Recoverable Sugar (kg/ha)

Recoverable Sugar (kg/ha)

Figure 9 — Example of the timing for either glyphosate or glufosinate applications to
prevent loss of root and sugar yield in sugarbeet. (The curved lines represent the effect
weeds have on sugarbeet yield dependent on either the amount of time that weeds remain
in the crop or the amount of time the crop remains weed-free. The dashed vertical lines
represent when herbicide should be applied. The solid vertical lines represent when
weeds begin to compete with sugarbeet and when the crop canopy closes.)

Apply Evaluate
Herbicide Herbicide | Wed
1 Control

 

Lil

 

 

 

 

 

 

 

 

 

 

closure

 

 

 

 

 

I I.
N
n ooooooo I- g
I ' ' I n _____ ~
g, Weedy I - Weed-Free ‘2
3 Period 1 . . ~ Period 3
C I " ~ ‘ . e
.2 s
I ‘ O
' 8
I a:
I Weeds
: becomes
I competitve Crop
I <: canopy
l
E

 

 

 

 

N
.5
O)
m

10 12
Weeks After Planting

58

Chapter 3

Use of Preemergence Herbicides with
Herbicide Resistant Sugarbeet

Abstract

Traditional weed management systems in sugarbeet follow a program approach.
Herbicides such as cycloate, pyrazon, and ethofumesate are applied preemergence to
provide residual control of annual weeds. Weeds not controlled with these ‘residual’
herbicides are removed using postemergence herbicides, cultivation, and hand-labor. The
objective of this study was to evaluate the potential importance or effect of several PRE
herbicide regimes in glufosinate and glyphosate resistant sugarbeet. Trials were
conducted at three sites with both glufosinate resistant and glyphosate resistant sugarbeet
in 1998 and 1999. Cycloate PPI, pyrazon PRE, ethofumesate PRE, or no PRE herbicides
were applied at recommended rates followed by two or three applications of glufosinate
POST at 0.29 to 0.4 kg ai/ha, or glyphosate POST at 0.63 kg ae/ha, or desmedipham and
phenmedipham at 0.56 kg ai/ha plus triﬂusulfuron at 0.0174 kg ai/ha. Glufosinate and
glyphosate were applied when weeds were two to four cm in height. Desmedipham and
phenmedipham plus triﬂusulfuron were applied when weeds were one to two cm in
height, and again with the addition of clopyralid at 0.105 kg ai/ha 7 to 14 days later.
Weed control, root yield, and recoverable sugar were evaluated for each herbicide
application regime.

Soil-applied preemergence herbicides delayed the necessity for the ﬁrst
application of glufosinate and glyphosate by three to nine days in six of 12 studies. PRE

herbicides followed by glufosinate or glyphosate improved the control of common

59

lambsquarters or redroot pigweed at three out of 12 sites compared with POST only
treatments. Common lambsquarters or redroot pigweed control increased at ﬁve out of
six sites in 1999 when PRE herbicides were followed by desmedipham and
phenmedipham plus triﬂusulfuron plus clopyralid compared with POST only treatments.
Sugarbeet yield or quality did not increase when PRE herbicides were followed by either
glufosinate, glyphosate, or desmedipham and phenmedipham plus triﬂusulfuron plus
clopyralid POST compared with POST only treatments.

Introduction

The recent development of sugarbeet varieties that are resistant to either of the
herbicides glyphosate or glufosinate has introduced the ﬁrst major change in weed control
programs for this crop in over 25 years. Nearly all of the herbicides currently used in
sugarbeet production were developed in the late 1960’s and have a narrow margin of
selectivity. Non-optimal environmental conditions can alter herbicide phytotoxic effects,
producing crop injury (Schweizer and Dexter 1987). Besides causing injury, traditional
sugarbeet herbicides have the ability to control only very small weeds when applied
postemergence (Wilson 1998). The precise timing required and the need for several
reduced rate applications to avoid crop injury make current postemergence treatments less
than ideal. Despite these limitations there has been a gradual shift towards the use of
more postemergence herbicides (Grifﬁth 1994). Unlike traditional postemergence
sugarbeet herbicides, glyphosate and glufosinate do not injure the respective resistant
crop cultivar and have the ability to control large weeds, making this technology the next

step in the evolution of weed control programs.

60

Glyphosate and glufosinate have herbicidal activity on most species of plants and
can be used for postemergence weed control in genetically altered, resistant crop
varieties. Crcps that are resistant to glyphosate are sold under the trademark Roundup
Ready®, and glufosinate resistant crops are known as Liberty Link®. Each has a unique
mode of action and can only be applied to the appropriate resistant variety.

The high cost of traditional sugarbeet herbicides such as desmedipham, pyrazon,
and ethofumesate has led many growers to apply these products in a band over the row to
reduce the amount of active ingredient (Schweizer and Dexter 1987). Weeds are only
controlled within this band and cultivation between the rows controls the remaining
weeds. Glyphosate and glufosinate are less expensive than traditional postemergence
herbicides and could be applied as broadcast treatments. Therefor the entire ﬁeld could
be treated and cultivation would not be needed for weed control. Though the price of
either herbicide is less, there are additional costs associated with a Roundup Ready or
Liberty Link system. A technology fee would be assessed when seed is purchased (J.
Kauffman, Monsanto, personal commtmication, August 1998). This additional cost for
seed must be considered when the costs of weed control are evaluated.

Weed control in sugarbeet often follows a program approach where preemergence
herbicides are applied at planting in combination with postemergence herbicides later in
the season. Preemergence herbicides stay biologically active in the soil, controlling
germinating weed seedlings. The pre-mixture of the postemergence herbicides
phenmedipham and desmedipham controlled weeds more effectively when applied to
areas previously treated with the preemergence herbicide cycloate (Dexter 1994). The

greatest relative reduction in broadleaf weed density occurred when preemergence

61

herbicides were applied at planting and followed with a postemergence herbicide
treatment (Wilson 1992). The number of postemergence treatments and the need to
include a preemergence herbicide to achieve the most cost-effective weed control varied
according to weed density (Miller et al. 1997).

Neither glyphosate nor glufosinate remain active in the soil (WSSA 1994), and
therefore have no residual effect on later emerging weed seedlings. Since glyphosate and
glufosinate control only weeds that are emerged, preemergence herbicides would provide
residual control of new weed seedlings.

The objective of this study was to evaluate weed control and yield of glyphosate
or glufosinate resistant sugarbeet following either full or half of the recommended use
rates of cycloate, pyrazon, ethofumesate, and mixtures thereof followed by
postemergence applications of glyphosate or glufosinate. Treatments were also
established to evaluate weed control when preemergence herbicides were applied as part
of a traditional weed management system. We were interested in determining if
preemergence herbicides would delay the ﬁrst postemergence herbicide application,
reduce the number of postemergence herbicide applications, give greater weed control, or
affect sugarbeet yield and quality. We also were interested in evaluating the costs
associated with the use of preemergence herbicides in glyphosate resistant and
glufosinate resistant sugarbeet.

Materials and Methods

Research was conducted at three sites in Michigan in 1998 and 1999 in

c00peration with Michigan and Monitor Sugar Companies (Table 7). Each of the

locations consisted of one glyphosate resistant sugarbeet study and one glufosinate

62

resistant sugarbeet study. The ﬁrst site was established at the Michigan State University
Saginaw Valley Bean and Beet Research Farm in Saginaw County. Michigan Sugar’s
sites were located in a grower’s ﬁelds in Saginaw County, while Monitor Sugar’s sites
were located in Bay County. Each study at each site was arranged as a randomized
complete block design with four replications. The dominant weeds at each site were
redroot pigweed, Amaranthus retroﬂexus, and common lambsquarters, Chenopodium
album.

In 1998 sugarbeet was planted in 71 cm or 76 cm wide rows with a seed spacing
of 11 cm between the dates of April 28 and May 11 (Table 7). In 1999 sugarbeet was
planted in 71 cm or 76 cm rows with a seed spacing of 6 cm, between the dates of April
28 and May 4. Sugarbeet was thinned to a spacing of 15 cm in 1999, approximately four
weeks after planting. The glufosinate resistant sugarbeet variety, Beta 891LL, and the
glyphosate resistant variety, HM RH3RR, were planted at each location. Plots were 9.1
m long and four rows (2.85 to 3.1 m) wide. Herbicides were broadcast with a tractor
mounted compressed air sprayer. Cycloate was incorporated prior to planting using a
Kongskilde Triple-K (Kongskilde Corp., Bowling Green, OH 43402). The preemergence
herbicides pyrazon and ethofumesate were applied after planting at both full and half of
the suggested use rates. The recommended use rates for cycloate are 3.36 to 5.04 kg ai/ha,
pyrazon are 3.36 to 5.6 kg ai/ha, and ethofumesate are 1.68 to 2.24 kg ai/ha.

Prior to the ﬁrst postemergence herbicide application, the number of weed
seedlings in a 18 cm by 69 cm quadrant placed over the row was recorded. A standard
postemergence treatment of desmedipham and phenmedipham at 0.56 kg ai/ha plus

triﬂusulfuron at 0.0174 kg ai/ha was applied when weeds were 1.25 cm in height. This

63

 

 

was followed seven to 14 days later with an application of desmedipham and
phenmedipham plus triﬂusulfuron plus clopyralid at 0.105 kg ai/ha. Glyphosate and
glufosinate were applied postemergence at 0.63 kg ae/ha and 0.29 to 0.4 kg ai/ha
respectively when weeds were 2.5 cm tall (Table 8). A second postemergence application
of glyphosate or glufosinate was made when weeds again reached 2.5 cm in height.
Percent injury to the crop was visually rated, with values greater then zero representing
severity of crop stunting. Weed control ratings were determined visually for each weed
species two and four weeks after the second glyphosate and glufosinate application.

In 1998 the Michigan Sugar Co. site did not include a standard postemergence
treatment. By request of the cooperator, a third application of glufosinate was made at
this location to prevent weeds from going to seed. Standard postemergence treatments
were not planned for the glyphosate resistant sugarbeet at the Monitor Sugar location, due
to a shortage of sugarbeet seed. In 1999 two additional herbicide treatments were
included to compare two versus three postemergence applications of glyphosate or
glufosinate alone (Table 9).

In 1998 plots at both the Michigan Sugar Co. and Monitor Sugar Co. locations
were machine harvested for yield October 5 through October 9. The third site at the
Saginaw Valley Bean and Beet Research Farm was not harvested due to stand loss from
disease. In 1999 sugarbeet was harvested from all locations October 5 through October
15. The glyphosate study at the Monitor Sugar location was not harvested because of
inadequate stand due to poor crop emergence. In both years Michigan Sugar Company
analyzed all sugarbeet samples for sugar content and purity (Michigan Sugar Co.,

Carrollton, MI 46724).

All data were recorded and initially subjected to analysis of variance using
Pesticide Research Manager version 5 in 1998 and Agriculture Research Manager 6 in
1999 (Gylling Data Management, Brookings, SD), and means separated using Fisher’s
Least Signiﬁcant Difference (LSD) at the 0.05 level (Appendix, Tables 16-27). Weed
control data was arcsine transformed prior to further analysis. An F -max, Hartley’s, test
was used to determine if sites could be combined (Kirk 1982). Data could not be
combined due to year by site by treatment interactions. Data from each study was again
subjected to analysis of variance as a two factor randomized complete block designs
using the general linear means procedure in SAS (SAS Institute, Cary, NC 27513).

Pairwise comparisons were made using F-tests at the 0.05 level.

Results and Discussion

Full versus Half &th

There was no difference in weed control when comparing 11111 and half use rates of
preemergence herbicides in 10 out of 12 studies. P-values for comparisons of each of
these 10 studies ranged from 0.14 to 0.96. In the other two studies there was no
biological signiﬁcance to the difference between full and half rates. Weed control
exceeded 97% for every treatment in the glufosinate study at the Michigan Sugar location
in 1998, and the p-value for the full versus half rate comparison was greater than 0.05. In
the glyphosate study at the Monitor Sugar location in 1998, replications of the half rate of
ethofumesate were absent ﬁorn the study, which resulted in this treatment being
signiﬁcantly different. We determined this to be due to human error and was not a result

of a biological difference between full and half rate treatments. Weed control and yield

65

data for all treatments can be found in the appendix. Data from treatments using full rates
are therefore presented in this chapter.
Delay in Postemergence Applications

In 1998 preemergence herbicides delayed the ﬁrst application of glyphosate or
glufosinate by three to nine days in two out of the six trials (Table 8). This delay
occurred in the glufosinate resistant sugarbeet at the Michigan State University and
Michigan Sugar Company sites. In both instances this delay was seen in the two earliest
planted studies (Table 7). Below average precipitation during the spring and summer of
1998 was a problem for many sugarbeet growers in Michigan. Sugarbeet planted prior to
April 30, 1998 received adequate rainfall to activate preemergence herbicides in the soil.
Glyphosate resistant sugarbeet was planted after May 2, 1998 at both sites and less then
2.6 cm of rain fell during the month of May. Therefore, preemergence herbicides in the
glyphosate studies were not activated and weed emergence was not delayed.

In 1999 preemergence herbicides delayed postemergence applications of
glyphosate and glufosinate in four out of six studies (Table 8). Preemergence herbicides
did not delay postemergence application of glyphosate or glufosinate at the Michigan
Sugar Company site because velvetleaf, Abutilon theophrasti, was not controlled by the
preemergence herbicides and exceeded 1.25 cm in height when sugarbeet was at the
cotyledon growth stage.

N fo itio Postemer en e A lications

Weed control and sugarbeet yield in treatments that included a preemergence

application of cycloate, ethofumesate, or pyrazon followed by two postemergence

applications of glyphosate or glufosinate were compared to no preemergence herbicide

66

followed by two to three postemergence applications of glyphosate or glufosinate. The
use of a preemergence herbicide could replace an additional postemergence application of
glyphosate and glufosinate in one of four studies (Table 9). Preemergence herbicide
followed by two postemergence applications of glyphosate improved the control of
redroot pigweed compared with two postemergence applications of glyphosate at the
Monitor Sugar site in 1999 (Tables 9 and 10). Glyphosate resistant sugarbeet at this site
was not harvested due to a poor stand as a result of poor crop emergence. Weed control
obtained from three applications of glyphosate or glufosinate or from a preemergence
herbicide followed by two postemergence applications of glyphosate and glufosinate was
not less than 96% in any other study. Thus, preemergence herbicides followed by two
postemergence applications of glyphosate or glufosinate provided weed control
equivalent to three applications of glyphosate or glufosinate. A third postemergence
herbicide application was necessary only when the crop stand was inadequate.

Preemergence herbicides increased weed control in glyphosate resistant sugarbeet
at the Monitor Sugar site in 1999 (Table 10) and in glufosinate resistant sugarbeet at the
Michigan State University and Michigan Sugar Company sites in 1998 (Table 11).
Beneﬁts from preemergence herbicides were observed at the same sites where the ﬁrst
postemergence application of glufosinate was delayed. The use of cycloate,
ethofumesate, or pyrazon followed by two applications of glufosinate provided better
control of common lambsquarters then glufosinate alone at the Michigan State University
site. Glufosinate was applied three times at the Michigan Sugar site; however, redroot
pi gweed control increased when cycloate plus pyrazon preceded postemergence

applications compared with no preceding herbicide. The use of preemergence herbicides

67

gave greater weed control compared with glyphosate and glufosinate alone in only three
out of 12 studies in 1998 and 1999 (Tables 10 and 11). In 1998 greater weed control was
seen in the earliest planted studies, while in 1999 preemergence herbicides increased
weed control only in areas with poor crop stand.
anvgtignal Pgstemergengg Erggrﬂns

A split application of desmedipham and phenmedipham plus triﬂusulfuron plus
clopyralid applied to glyphosate and glufosinate resistant sugarbeet provided 83% or
greater control of common lambsquarters and redroot pigweed in 1998 at all sites (Table
12). Lack of precipitation in 1998 resulted in fewer weed ﬂushes, and preemergence
herbicides followed by postemergence herbicides did not provide better weed control
then weed management programs using only postemergence herbicides. In contrast the
use of preemergence herbicides in a conventional weed management system
(desmedipham and phenmedipham plus triﬂusulfuron plus clopyralid) increased weed
control in ﬁve of six studies in 1999 (Table 12). This supports conclusions by Wilson
(1992) and Miller et al. (1997) where weed control increased when preemergence
herbicides were followed by postemergence herbicides.
Suggbeet Yield

Preemergence applications of cycloate, ethofumesate, and pyrazon followed by
glyphosate or glufosinate did not affect sugarbeet root yield or recoverable sucrose
compared with glyphosate or glufosinate alone (Tables 13 and 14). Similarly,
preemergence herbicides did not affect the yield of glyphosate and glufosinate resistant
sugarbeet treated with conventional postemergence herbicide regimes. P-values for these

treatments ranged from 0.20 to 0.84 (data not shown). This supports research by Miller et

68

al. (1997) where the use of preemergence herbicides decreased hoeing time, but did not

increase sugarbeet yield.

Cost Comparisgn

The cost for each herbicide program was calculated using information provided
by local agri-chemical dealers in 1998, and from the 1996 Doane’s Agricultural Reports
(DAR 1996). Because preemergence herbicide regimes were not associated with higher
sugarbeet yield in any trial in this study, the least expensive herbicide combination was
therefore be the most cost effective. Glyphosate applied twice provided 87% or more
control of common lambsquarters and redroot pigweed in both 1998 and 1999. Herbicide
prices show that an additional broadcast application of glyphosate ($26.25-$33.80/ha) is
less expensive then a banded application of ethofumesate or pyrazon ($47 .40-$79.60/ha)
or a broadcast incorporated application of cycloate ($77.40-$103.75). Therefore the use
of preemergence herbicides preceding glyphosate application in glyphosate resistant

sugarbeet was not justiﬁed.

In glufosinate resistant sugarbeet one broadcast application of glufosinate would
cost $56.50/ha in 1998 and 1999. The cost for an equivalent rate of this herbicide
decreased to $40.30/ha in 2000. One application of cycloate ($77 .40-$103.75) would be
more expensive then one additional glufosinate application. Depending on which years
prices are used, the cost for one application of glufosinate would be less than or equal to
the cost of one application of either ethofumesate or pyrazon ($47.40-$79.60) applied in a
band. Preemergence herbicides should be considered as weed control Options when
planting glufosinate resistant sugarbeet only if their application could be substituted for

later postemergence applications of glufosinate. However, predicting the ability to

69

substitute a preemergence herbicide for one or more postemergence applications of
glufosinate is difﬁcult. For example, dry growing conditions in 1998 resulted in
decreased crop growth and poor herbicide performance. Regardless of whether
preemergence herbicides were used, at one site additional glufosinate application were
needed to maintain weed control resulting in higher herbicide cost. The use of
preemergence herbicides improved annual weed control at a second site, where as weed
control was not increased at a third location. Favorable weather conditions in 1999
resulted in rapid growth of sugarbeet. During this season, two postemergence
applications of glufosinate alone were adequate for control of weeds and for protecting
crop yield. Therefore, the decision to apply preemergence herbicides can not be made
with any certainty of incurring a beneﬁt because weed density, crop stand and vigor are
unlmown at the time. There is also less justiﬁcation for using preemergence herbicides in
glufosinate resistant sugarbeet as the price of glufosinate decreases.

Growers considering this weed management system should also consider the
additional expenditure for technology fees associated with herbicide resistant sugarbeet
varieties. Companies may chose to charge additional fees for transgenic material, in an
effort to recover development costs. These fees are levied when growers purchase seed
and must be paid regardless of whether glyphosate or glufosinate are applied. In the case
of sugarbeet production the amount paid in technology fees could be larger then the
actual cost for herbicides, since this crop does not have the many price competitive
products that are available for corn or soybeans. Like any new product, technology fees
will be set according to what the market will accept. The average expenditure for

agricultural chemicals for sugarbeet production in the Great Lakes Region was $149.75

70

per hectare in 1996 (Ali 1999). When this cost is compared to the relatively low cost of
glyphosate or glufosinate, it becomes apparent that these technology fees may become
substantial. Estimates for the technology fees associated with glyphosate resistant
sugarbeet are $80 per unit of seed. Typically growers plant 0.75 to 1.5 units of seed per
hectare. This translates into an additional cost of $60 to $120 dollars per hectare (J.

Kauffrnan, Monsanto, personal correspondence, August 1999).
Conclusion

Our studies show that weed control programs without preemergence herbicides
will likely require two or three postemergence applications of glyphosate or glufosinate to
provide full-season weed control. In some cases, preemergence herbicides such as
cycloate, ethofumesate, and pyrazon did delay the need for the ﬁrst postemergence
herbicide application by three to nine days or did reduce the number of postemergence
herbicide applications needed. This is advantageous when using traditional
postemergence sugarbeet herbicides such as desmedipham and phenmedipham plus
triﬂusulfuron plus clopyralid. Preemergence herbicides used prior to a traditional
postemergence herbicide improved weed control at ﬁve out of six sites in 1999. The
lower cost and greater effectiveness in controlling larger weeds associated with
glyphosate or glufosinate negate these advantages.

In 1998 and 1999 there was no difference in weed control or sugarbeet yield in
herbicide resistant sugarbeet treated with full compared with half rates of preemergence
herbicides. Cycloate, ethofumesate, and pyrazon increased weed control in only 25% of
the studies and did not improve root yield or recoverable sucrose. A third application of

glyphosate or glufosinate provided excellent control of annual broadleaf weeds in the

71

absence of the customary use of preemergence herbicide applications. Though
preemergence herbicides should be considered as a useful tool for weed control in
sugarbeet, glyphosate and glufosinate are each less expensive and offer greater crop
safety with a wider spectrum of weed control.

Though glyphosate and glufosinate are each inexpensive when compared with the
cost of traditional sugarbeet herbicides, their associated weed management systems
should not be considered by the grower as less expensive. Technology fees added to the
cost of seed must be considered as a part of the expenditure for weed control. These fees

may negate the reduced cost of the herbicides.

72

Literature Cited

Ali, MB. 1999. US. Sugarbeet per-acre costs of production, 1996-1997. NDSU, 1998
Sugarbeet Research and Extension Reports. 29:157-159.

Dexter, A.G. 1994. History of sugarbeet (Beta vulgaris) herbicide rate reduction in
North Dakota and Minnesota. Weed Technol. 82334-337.

Doane’s Agricultural Report Newsletter. 1996. Estimated machinery operating costs,
1996. 59222-5.

Griffiths, W. 1994. Evolution of herbicide programs in sugarbeet. Weed Technol.
82338-343.

Kirk, RE. 1982. Page 78 in Experimental Design. Brooks/Cole. Monterey. CA. 911 p.

Miller, SD, K.J. Fomstrom, and L.J. Held. 1997. Preplant and postemergence herbicide
systems in Wyoming sugarbeet. J. Sugar Beet Res. 3421-19.

Schweizer, BE. and A.G. Dexter. 1987. Weed control in sugarbeets (Beta vulgaris) in
North America. Weed Sci. 32113-133.

Weed Science Society of America. 1994. Pages 147-152 in Herbicide Handbook. 7“ ed.

Wilson, R.G. 1992. Sequential herbicide application for weed control in sugarbeets. J.
Sugar Beet Res. 2921-7.

Wilson, R.G. 1998. Postemergence Herbicide Tinting for Maximum Weed Control in
Sugarbeet. Journal of Sugarbeet Research. 35:15-27

73

Table 7 - Soil series, type, organic matter, and planting dates for glufosinate and
glyphosate resistant sugarbeet at each location in 1998 and 1999.

 

 

 

-------- Site-------- Soil --------------Planting--------------
Location Year Series Type OM' Gluf" Glyt‘ Row Plant
Width Spacing
(%) (date) (date) (cm) (cm)
Michigan 1998 Zilwaukee Silty- <3 4/27" 5/1 1‘l 71 1 1
State Univ. clay
loam
Michigan 1998 Sloan- Silt >3 4/28 5/6 71 l 1
Sugar Co. Ceresco loam
Monitor 1998 Londo Loam <3 5/7 5/7 76 15‘
Sugar Co.
Michigan 1999 Zilwaukee Silty- >3 4/28 4/28 71 15‘
State Univ. Mistequay clay
Michigan 1999 Sloan Silt >3 4/30 4/30 71 15‘
Sugar Co. loam
Monitor 1999 Londo Loam <3 5/4 5/4‘I 76 15‘
Sugar Co.

 

‘ OM — organic matter

b Gluf — glufosinate resistant sugarbeet
° Glyt — glyphosate resistant sugarbeet
" Trial could not be harvested due to stand loss.

° Trials were thinned from a 6 cm spacing.

74

Table 8 — Dates of fust glyphosate and glufosinate application following preemergence
applications of cycloate, ethofumesate, and pyrazon at the Michigan State University,
Michigan Sugar Co., and Monitor Sugar Co. sites in 1998 and 1999.’

5052.8 - 54E 6858.33 1.35 .280:me 1 50 63883060 1 05m .032vo 1650 62036: 005908005 0: 1 0E 02 e

 

 

 

 

 

 

 

 

 

 

 

 

 

 

- - 25 25 - - - - as an - - c9555
me 2e 25 25 :e :e 25 25 85 Re New :5 e§n+o£m
ewe was 5 to e to Re. Be 5 to e to 55 an «me P :e in
me we - - :e :e e :m e :n - - e :m P :e osm

- - e :m e to :0 :e - - Em So «we a :e .96
85 men 25 25 Re Re 25 25 NS EB 25 :5 man oz
5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0

29.5.2 55.5.5. 5.0.2 29.5.2 55.5.5. 5.0.2
nee? wees

 

76

Table 9 — Common lambsquarters and redroot pigweed‘ control and root yield of
herbicide resistant sugarbeet following preemergence applications of cycloate,
ethofumesate, pyrazon, or no preemergence herbicide followed by postemergence
applications of glyphosate or glufosinate” at the Michigan State University and Monitor
Sugar sites in 1999.

850 085 00:09. 805802» .0 80809:» I .8m m .836 00:09. 805802» .0 Samoan—>3 I .80 N 9
005.03 I 53 6358.33 I .35 6.802%.w I .30 6.085050 I 05m 6.00.0.8 I .96 6203.0: oucowuoﬁooa 00 I 8... 02 ..
033w... 80.62 I BE .ﬁogcmnﬁa. 008800 I 0.00 .

 

 

 

 

 

 

 

..N 3. N... - N... NN E ...m a. a... N. 3 2. >0
.. ...Nm N 8. a a - a 8. a a 2. 52 a 8. N 2.. a S: a 8. a 2.. .8. N e
52.1050
an wém a mo 0 - a a . a m m . w a .mom
8 8. 3 3% 3 8. 02. 2.. 2.. N 2.5..
a 0% «8. Na - woo. «8. 50% «8. d.8. 3.: woo. woo. .8..N
2 250
- - - - - - N NE N 8. a 2.. N ...NN a 2.. a 8. .8. N
2 .020
2. .5 m 8. a Na - a 8. a 8. 2. N.NN a .5. a 8. N NE a 8. N 2.. 0.20.. N
a. New a 8 a a - .. Na N 3 a. 0.9 a 8 a 8. a «.2. a 8. a 8. 0.8.. N
o 0.2 - - - - - o 09. - - .. Sm - - 5.5
.252. .2... .2... .232. .2. .2... .252. .2... .2... .232. .2... .2...
22> 3.5. 200 22> 3.5. 28 22> 3.5. 28 22> 3.5. 200
80¢ .00”. .03. .03.
.......... .. 20.......... 50 5.0 2.0
.00 Swsm 8:202 >25 88m 5320.2

 

78

Table 10 — Control of common lambsquarters and redroot pi gweed' at the Michigan State
University, Michigan Sugar, and Monitor Sugar sites in 1998 and 1999 from cycloate,
ethofumesate, pyrazon, or no herbicide preemergenceb each followed by glyphosate.

79

0000...... - 00?. 6.8083050 I 0....m. 6.00.9.0 I .0>U 60.0.0.2. 000090800... 0.. I 0.... 07. ..

.0003»... .0800. I 3.5. 80800088... 008800 I 0.00 ..
.96. mod 0... .0 00000.00. 5.500.008 003 .0880 .0003 ...

 

 

0.0 0.... - - - - m... 0.0, 0.0. 8.. mm ..m 2..>0
8... 8.0 - - - - .2... .0... N0... 8... 8... E... 8.2,-..

- - - - - - - - 8 8. - - c5180
.8. 8 8. 8 8. 8. 8 8 8. 8 8. 8. 8.0650
.8. 8 - - 8. 8. 8. 8 8 8 8. 8. in.
.8. 8. - - 8. 8. 8. 8 - - 8. 8. 05m.

- - - - 8. 8. - - 8 8. 8 8 .80
8 8 8. 8. 8. 8. 8 8 8 8 8. 8. mm... 02
.2... .2... .2... .2.. .2. .2.. .2.. .2... .2... .2... .2... .2.

 

38m. 0.00 39m 0.00 38m. 0.00

5200.2

80.6.5. .00....

 

 

mam F

39m 0.00 38m 0.00 2.9m. 0.00
82:05. 000.50.: .30.).
000..

 

 

 

80

Table 11 — Control of common lambsquarters and redroot pigweed‘I at the Michigan State
University, Michigan Sugar, and Monitor Sugar sites in 1998 and 1999 from cycloate,
ethoﬁimesate, pyrazon, or no herbicide preemergenceb each followed by glufosinate.

81

0000.03 - 5%.. 6.8088050 I 8.5 6.00.0.3 I .000 60.0.0.0: 000030800... 0.. I 0... 02 0
0002.80 .0800. I 38% 8080000080. 80800 I 0.0.0 a
.96. no... 0... .0 00000.08 DES—.880 003 3.800 0003 ...

 

 

 

- 0.0 - - ...0 - ...0 0... 0.. ..0. 0.0 0.0 2..>0

- 00.0 - - 0.0 - .00 .0... 8.0 8.0 8.0 .80 02.2,-..

- - - - - - - - .8. 8 - - 5.0.9.0
8. 8 8 8 8. 8. 8 00 .0 .0 8. .8. 00.9.8.0
8. 8 - - .0 8. ..0 8 00 0. .0 .00 E...
8. 8 - - 8. 8. 8. 8 - - 8. ..0 02m.
- - - - 8. 8. - - .0 8 8. .8 0.0
8. 8 8 00 8 8. 8 00 ..0 00 8 .0 man. 02
.2. .2... .2. .2. .2. .2... .2. .2... .2. .2. .2. .2.
38m 0.00 2.80. 0.00 38m 0.00 38m 0.00 2.8m 0.00 2.8m. 0.00

5.82 80.6.2 0.0.2 5.8.2 80222 0.0.2

 

 

mam.

 

wmm.

 

 

82

Table 12 - Control of common lambsquarters and redroot pigweed' at the Michigan State
University and Monitor Sugar sites in 1998 and the Michigan State University, Michigan
Sugar, and Monitor Sugar sites in 1999 from cycloate, ethofumesate, pyrazon, or no
preemergence herbicide” followed by desmedipham and phenmedipham plus
triﬂusulfuron plus clopyralid applied to glyphosatec and glufosinated resistant sugarbeet.

83

.00...0m80 80.0.00. 0.080008% I 08.0 0
000.030 80.0.00. 0.000882% I 0:0 0

8000.20. - 80%.. 6.000839% I 05m. 6.00.020 I .020 60.05.08 008080800... 08 I 0... 07. 0
00028... .0000. I 3.5. 8080800880. 80800 I 0.00 ..
..0>0. mod 0... .0 00000.08. 208000830 003 .0888 0003 ...

 

 

0.: 0.0 0.0 0.: 0.0. 0.8 0.0. ..0. 0.0 0.0 ... 0.0 0.: 0... - 0..- 00 ...0 2:6
00... .8... 80... 00... 8... 00... 0.... 0.... 8... 3.... .8... 00... 0.... .0... - .0... 0.... 8... 8.0.-..
- - - - ...8 ...00 .0 00 - - - - - - - - - - 5......05

oo. ...oo. ...0 .0 ...mw 0mm om mm .50 oo. .00 co.
mm .00 «00 .3 ...wh ...w .w mw ...mm 00. ...oo. oo.

oo. ...oo. ...oo. ma - I - - ...oo. oo. *oo. oo.

- - - - ...0. ...8 .0 8 ...8 8. ...00 8.
00 00 00 00 .0 00 0. 0. 00 00 0. 00
.2. .2. .2. .2. .2. .2. .2. .2. .2. .2. .2. .2.

3.5. 0.00 3...”. 0.00 3...”. 0.00 3...... 0.00 3.5. 0.00 3.5. 0.00

.20 2.... .20 ...0 .20 80
......... . 3.8.2 000.00.: $80.25.----

.000.

 

 

 

 

00 8 8. 8. 8 00 00.03.08
00 8 8. 8. 8. 8. .5...
00 .0 8. 8. 00 8 208
- - 8. 8. 8. 8. 0.0
8 00 8. 8 .0 8. 0.8.. oz

.2. .2. .2. .2. .2. .2.
3.5. 0.00 3.5. 0.00 3...... 0.00

08.0 .30 3.0
8.80.). ........ 00.0,. ........

 

 

 

84

Table 13 — Root yield and recoverable sucrose of sugarbeet following application of
cycloate, ethofumesate, pyrazon, or no preemergence herbicide' followed by glyphosate
at the Michigan Sugar and Monitor Sugar sites in 1998 and the Michigan State University
site in 1999.

85

80000... - 80.... 6.00.08.80.00 I 0.0.. 6.00.9.0 I .000 60.0.0.0: 0080w.08.00... 08 I 0... 07. a

 

 

 

- - - - 00.. 00.. .0... .0.... 00... 0.0. - - 2. >0

- - - - 0.... .0... 00... .0... .0... .0... - - 022,...

- - - - - - - - 0000 0.00 - - 6.020...

- - ..0... 0.00 ...0 ..0. 080 3.0 00.0 ...0 - - 00.002...

- - - - 3.00 0.00 00.0 0.00 0.8 ...00 - - .8...

- - - - .000 .... ...0 ...0 - - - - 8.0

- - - - ...0 0.0. - - 03.0 ...0 - - .0...

.. - .80 0.00 .000 0.00 8.0 ...0 0.0.. ...0 - - 00. oz
.200... .0202. .200... .0200... .200... .2002. .020... .200... .020... .2002. .200... .2202.
000.86 0.0. .w 000.25 0.0. .r 0.00.0.5 0.0. > 08.0% 0.0. > 03.2% 0.0. > 000.08m 0.0. >

.03. .000. .00.”. .03. .00.". .000.
.222). 5022.). 0.0.2 .322). 8022.). .00.).

 

 

 

 

mam. wmm.

 

86

Table 14 —~ Root yield and recoverable sucrose of sugarbeet following application of
cycloate, ethofumesate, pyrazon, or no preemergence herbicide‘ followed by glufosinate
at the Michigan Sugar and Monitor Sugar sites in 1998 and the Michigan State University
and Monitor Sugar sites in 1999.

87

80000... - 8N... 600.00.88.30 I 0.0m. 6.00.9.0 I .000 60.0.2.2. 8800.08.00... 08 I 0... 07. 0

 

 

00.0 00.. - - ...0 0.0 00.0. 0.... 00.0. ...0. - - 2. >0
00... 00... - - 00... 00... 00... 00... ..0... .0... - - 020i.

- - - - - - - - 0000 0.00 - - 00.0200
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88

Chapter 4

Effect of Cultivation on Weed Emergence
In Glufosinate Resistant Sugarbeet

Abstract

Weed control in sugarbeet involves banded applications of herbicides combined
with cultivation. Cultivation as a weed control strategy is not needed with the
introduction of herbicide resistant sugarbeet. Growers have expressed an interest in
continuing to cultivate sugarbeet. The purpose of this study was to evaluate the effect of
cultivation timing and the number of cultivation(s) on annual weed emergence in
glufosinate resistant sugarbeet. Glufosinate was applied three times at 400 g ai/ha in all
treatments. The number and species of weeds in a 25 cm by 76 cm quadrant were
counted prior to each glufosinate application or cultivation, and every 10 to 14 days
afterwards. The dominant weed species were giant foxtail, common lambsquarters,
redroot pigweed, and Pennsylvania smartweed.

In 1998 weed emergence increased in August and September where treatments
were cultivated after the ﬁnal glufosinate application. Cultivation prior to a POST
application of glufosinate did not result in greater late season weed emergence. In 1999
weed emergence between June 24 and July 14 was greater in treatments where plots were
cultivated prior to the ﬁrst glufosinate application. Cultivation did not produce greater
weed emergence in August and September compared to treatments with no cultivation.
Precipitation and sugarbeet growth rate differed between 1998 and 1999. Emergence of
small-seeded broadleaf weeds such as common lambsquarters was affected by

cultivation. There was no difference in the number of weed seedlings present at the end

89

 

of the season in cultivated plots compared with non-cultivated plots in which glufosinate
was applied two to three weeks after the ﬁnal cultivation.
Introduction

Cultivation between the rows of the crop is a common technique for weed control
in sugarbeet. With the introduction of sugarbeet varieties that are resistant to herbicides
such as glufosinate or glyphosate, cultivation as a weed control strategy may no longer be
required. This is because these herbicides may be applied broadcast, providing excellent
weed control at a competitive cost. In spite of this new technology, growers have

expressed an interest in continuing to cultivate sugarbeet. Many growers employ a

 

“cutaway” cultivation early in the season to aerate and loosen the soil allowing young
sugarbeet plants to get established. In addition to weed control, cultivation may be used
to loosen the soil, push soil around the sugarbeet plants to aid in harvest, and to enhance
the aesthetics of the crop in the ﬁeld.

One argument against using cultivation with herbicide resistant crops is that
tilling the soil may increase the emergence of new weed seedlings (Egley and Williams
1990). Neither glufosinate nor glyphosate have residual soil activity and thus only
control emerged weeds (WSSA 1994). New weed emergence after herbicide application
could translate into decreased control. Seed germination and dormancy is complicated
and can be inﬂuenced by many factors including soil temperature, soil moisture, and
exposure to light (Baskin and Baskin 1990, Alrn et al.1993, Salisbury and Ross 1992,
Taiz and Zeiger 1998). Cultivation can affect the distribution of seeds or the
environment needed for germination (Egley 1986, Egley and Williams 1990), thereby

inﬂuencing the emergence of weeds.

90

One way in which tillage may inﬂuence seedling emergence is by affecting soil
temperature and moisture. Research has shown a relationship between weed grth and
soil temperature and moisture (W iese and Binning 1987). Less tillage can result in lower
soil temperature and greater soil moisture (Oryokot et al. 1997c). Reducing tillage
concentrates weed seeds near the soil surface (Clements et al. 1996). As temperature
increases above a minimum threshold the rate of seed germination and shoot elongation
is increased. For some weed species there is a temperature above which germination and *
elongation decrease (Oryokot et al. 1997b & 1997c). Temperature and moisture are also

known to inﬂuence secondary dormancy of some annual weeds. Low soil temperature i -

 

may break seed dormancy, while high temperatures induce dormancy (F orcella et a1.
1997). The actual effect of tillage on soil moisture, temperature, and therefore weed
emergence is somewhat limited. As an example, Amaranthus retroﬂexus seedlings are
physiologically restricted to germination depths of less then 2.5 cm. At shallow depths
heat and moisture transfer between the soil and atmosphere is rapid and reduces the affect
of tillage on seed germination (Oryokot et al. 1997a). These criteria may also limit the
effect of tillage on annual grasses such as Setariafaberi, which has its greatest
emergence from depths less then 1 cm (F ausey and Renner 1997).

Exposure to light is another seed emergence variable affected by tillage (Wesson
and Wareing 1969, Buhler 1997, Gallagher and Cardina 1998). Exposure to light can
break seed dormancy in many plant species. This requirement for light would keep
propagules that are buried more then a few centimeters from germinating, which is an
advantage for plant species with small seeds (Salisbury and Ross 1992, Buhler 1997).

Phytochrome which exists in two forms, phytochrome. red (Pr), and phytochrome far red

91

(Pfr), mediates the response of seeds to light (Ascard 1994). Phytochrome in the buried
seeds is in the inactive red-light absorbing form (Pr). Exposure to sunlight converts Pr to
Pfr, which results in a series of physiological events that lead to germination (Gallagher
and Cardina 1998, Taiz & Zeiger 1998). In research by Buhler (1997), emergence of
small seeded weeds such as Chenopodium album and Polygonum pennsylvanicum was
less when tillage was performed in the dark. The light environment during tillage did not
have an affect on the emergence of annual grasses such as Setariafaberi, or large seeded k...
broadleaf weeds such as Abutilon theophrasti. Similar results were reported by Ascard

(1994) in which the germination of some weed species was less where tillage implements

 

excluded light. Unlike Buhler however, Ascard’s experiments did not show lower C.
album germination when tillage was performed at night. Gallagher and Cardina (1998)
reported differences in emergence of some weed species when tillage was performed at
night versus during the day; however, these differences varied considerably. Though the
microclimate variable that accounted for the most variation in the emergence of C. album
was temperature, exposure to light prolonged non-dormancy (F orcella et al. 1997). Thus
the interaction between temperature, light requirement, and soil moisture on seed
germination is complex and varies by weed species.

The effect of cultivation on weed emergence may vary according to the time of
the year. When soil is cultivated there is a small proportion of the total seed bank which
is released ﬁ'om dormancy (Roberts 1984). Weeds such as C. album tend to appear more
frequently aﬁer spring tillage, and continue to appear whenever the soil is disturbed.
Temperature largely determines this seasonal pattern of emergence, however soil

moisture is an important factor required for germination (Roberts 1984).

92

The purpose of this study was to evaluate the effects of cultivation on the
emergence of annual weeds in sugarbeet. This information can then be used in
developing cultivation and herbicide programs to manage weeds in herbicide resistant

sugarbeet.
Materials and Methods
This study was conducted at the Michigan State University Agronomy Research

Farm at East Lansing, Michigan in 1998 and 1999. The ﬁeld was of a Capac (series) #-

sandy loam (55% sand, 30% silt, & 15% clay), with a pH that ranged from 6.9 to 7.2.

 

Organic matter ranged ﬁorn 1.8 in 1998 to 2.7 in 1999. The ﬁeld was chisel plowed the
previous fall and smoothed with a soil ﬁnisher. The soil was tilled again with a
Kongskilde Triple-K (Kongskilde Corp., Bowling Green, OH 43402) immediately prior
to planting. Beta variety 89OLL was planted to stand in 76 cm rows on May 7, 1998 and
May 4, 1999. Fertilizer (336 kg/ha of 19-19-19) was applied at planting. Plots were 18.3
m long and four rows in width.

Trials consisted of six treatments replicated three times. The study was designed
as a randomized complete block with repeated measures. The six treatments varied
according to the timing and frequency of cultivation (Table 15). All treatments received
broadcast applications of 400 g/ha of glufosinate plus 2.8 kg/ha ammonium sulfate. In
1998 the dates for these postemergence applications were June 8, June 18, and July 10.
In 1999 glufosinate was applied postemergence to sugarbeet on June 9, June 22, and July
12. The ﬁrst herbicide application was made ﬁve days after the initial cultivation. The
ﬁrst cultivation or cutaway was delayed in order to allow sugarbeet plants to grow

beyond the cotyledon stage. This was necessary in order to minimize crop damage with

93

the available cultivation equipment. Subsequent herbicide applications were made when
newly emerged weeds were two to ﬁve cm in height or if previously treated weeds were
not controlled.

Weed species were counted in a 25 by 76 cm quadrant placed randomly within the
plots. The position of the quadrant was marked with a ﬂag in order for subsequent weed
counts to be taken from the same area. Weeds were counted between the crop rows prior
to each herbicide application or cultivation. Weeds were counted every 10 to 14 days
until the end of September. Weed species include Setarr'afaberi (giant foxtail),
Chenopodium album (common lambquarters), Polygonum spp. (Pennsylvania &
ladysthumb smartweed), Amaranthus retroﬂaxus (redroot pigweed), Abutilon theophrasti
(velvetleaf), Ambrosia artemisiifolia (common ragweed), annual grasses, and broadleaf
weeds in the family Brassicaceae. In 1998, C. album accounted for approximately 20%
and S. faberi for approximately 60% of the emerged annual weeds. In 1999
approximately 10% of the emerged weeds were C. album and 65% S. faberi.

In 1998 weed density was recorded ﬁom June 2 until September 30. In 1999
densities were recorded from June 6 until September 24. The density of each individual
weed species on a speciﬁed date were subjected to analysis of variance using PRM 5 in
1998 and ARM 6 in 1999 (Gylling Data Management, Brookings, SD 57006). Separate
analysis for each date was required since this study contained repeated measures, and
experimental units were not independent from one another. Means were separated by a
least signiﬁcant difference at the 0.05 level. The average number of seedlings from
species displaying a signiﬁcant difference in emergence as a result of cultivation was

then graphed as a scatter plot using a Microsoft Excel spreadsheet (Microsoft, Buffalo,

94

on... .—
I

 

NY 14207). Graphing the data in this manner gave a visual representation of the change

in weed emergence over time.
Results and Discussion
The 1998 growing season was poor throughout much of Michigan. Below
average rainfall resulted in drought conditions which affected the growth of both
sugarbeet and annual weeds. Many sugarbeet growers experienced inconsistent crop
l

emergence, slow crop growth, and lack of canopy development. In contrast the 1999

‘Wc

season began with adequate rainfall and warm temperatures. Sugarbeet emergence and

growth was rapid, though the incidence of disease was more frequent. Control of annual i

 

weeds with glufosinate was excellent.

In 1998 total weed emergence was greater in plots where the ﬁnal cultivation
followed the last postemergence application of glufosinate (timings C & A+C, Figure
10). Differences in weed emergence were evident three to four weeks after the ﬁnal
cultivation. C. album emergence increased at the end of the season where plots were
cultivated after the ﬁnal glufosinate application (timings C & A+C, Figure 11).
However, cultivation did not inﬂuence (P=0.05) the emergence of S. faberi (Figure 12),
Abutr'lon theaphrasti, or Amaranthus artemisiifolia at any time during the season. Tillage
is reported to have inconsistent effects on the emergence of annual grass species such as
S. faberi (Buhler 1997). Soil temperatures above 17° C may induce secondary dormancy
in S. faberi (F orcella et al. 1997).

Early season weed densities did not reﬂect differences due to cultivation, because

frequent cultivation and herbicide applications removed seedlings. Cultivation prior to a

95

postemergence application. of glufosinate did not increase weed emergence in August and
September when compared with no cultivation (timings A, B, & A+B).

Similar results were seen during the 1999 season. Weed emergence between June
24 and July 14 increased when plots were cultivated prior to the ﬁrst herbicide
application (timings A & A+C, Figure 13). Treatments that included the second
cultivation had fewer emerged weeds due to seedlings being removed at a later date
(timings B & A+B, Figure 13). Most of the newly emerged weeds were annual grasses,
including S. faberr' (Figure 15). Moist soil conditions in 1999 may have resulted in cool
soil temperatures, allowing grasses to germinate. In contrast to 1998, the emergence of
C. album did not increase after the ﬁnal cultivation (Figure 14). In 1999 the sugarbeet
canopy completely covered the soil area between the rows. This shading may have
inﬂuenced weed germination by affecting soil moisture, solar radiation reaching the soil,
and temperature (Anderson and Nielsen 1996). The only weed that emerged after the
ﬁnal cultivation was Polygonum spp. (timing C & A+C, Figure 16). This was
unexpected since smartweeds emerge at low temperatures and are considered an early

emerging species (Buhler et al. 1997)
Conclusions

Literature suggests that cultivation may affect the emergence of several weed
species. Similar to research published by Buhler (1997), cultivation affected the
emergence of small seeded broadleaves such a C. album and Polygonum spp., and had
inconsistent effects on the emergence of annual grass, including S. faberi. In our studies
it took three to four weeks after the ﬁnal cultivation to see differences in weed

emergence. Cultivation did not affect late season weed emergence if glufosinate was

96

 

applied after the ﬁnal cultivation. This coincides well with an observation by Roberts
(1984), in which the rate of appearance for new seedlings returned to a “background”
level after soil cultivation released a ﬂush of weeds.

Cultivation may continue to be used in herbicide resistant sugarbeet. Growers
who plan on cultivating herbicide resistant sugarbeet varieties need to be aware that
glufosinate should be broadcast-applied approximately two to three weeks after the last

cultivation. t.

°\ WHO .

 

97

Literature Cited

Alm, D. M., E. W. Stoller, and L. M. Wax. 1993. An index model for predicting seed
germination and emergence rates. Weed Technol. 7:560-569

Anderson, R.L. and DC. Nielsen. 1996. Emergence pattern of ﬁve weeds in the central
great plains. Weed Technol. 10:744-749.

Ascard, J. 1994. Soil cultivation in darkness reduced weed emergence. Acta Hort.

372:167-177.

Baskin, J .M. and CC. Baskin. 1990. The role of light and alternating temperatures on

germination of Polygonum aviculare seeds exhumed on various dates. Weed Res. t
30:397-402. f.

Buhler, DD. 1997. Effects of tillage and light environment on emergence of 13 annual
weeds. Weed Technol. 11:496-501.

 

Buhler, D.D., R.G. Hartzler, F. Forcella, and J .L. Gunsolus. 1997. Relative emergence
sequence for weeds in corn and soybeans. Iowa State University Extension. Ames, Iowa.
SA-l 1. 4 pp.

Clements, D.R., D.L. Benoit, S. D. Murphy, and C. J. Swanton. 1996. Tillage effects on
weed seed return and seedbank composition. Weed Sci. 44:314-322.

Egley, G.H. 1986. Stimulation of weed seed germination in soil. Reviews of Weed Sci.
2:67-89

Egley, G.H. and RD. Williams. 1990. Decline of weed seeds and seedling emergence
over ﬁve years as affected by soil disturbance. Weed Sci. 38:504-510

F ausey, J .C. and K.A. Renner. 1997. Germination, emergence, and growth of giant
foxtail (Setariafaberi) and fall panicum (Panicum dichotomiﬂorum). Weed Sci. 45:423-
425.

Forcella, F., R.G. Wilson, J. Dekker, R. J. Kremer, J. Cardina, R.L. Anderson, D. Alm,
K.A. Renner, R.G. Harvey, S. Clay, and DD. Buhler. 1997. Weed seed bank emergence
across the corn belt. Weed Sci. 45:67-76.

Gallagher, RS. and J. Cardina. 1998. The effect of light environment during tillage on
the recruitment of various summer annuals. Weed Sci. 46:214-216.

Harvey, S. J ., and F. Forcella. 1993. Vernal seedling emergence model for common
lambsquarters (Chenopodium album). Weed Sci. 41:309-316.

98

Oryokot, J .O.E., S.D. Murphy, and OJ. Swanton. 1997a. Effect of tillage and corn on
pigweed (Amaranthus spp.) seedling emergence and density. Weed Sci. 45:120-126.

Oryokot, J .O.E., S.D. Murphy, A.G. Thomas, and OJ. Swanton. 1997b. Temperature and
moisture dependent models of seed germination and shoot elongation in green and
redroot pigweed (Amaranthus powellii, A. retroﬂexus). Weed Sci. 45:488-496.

Oryokot, J .O.E., L.A. Hunt, S. Murphy, and OJ. Swanton. 1997c. Simulation of
pigweed (Amaranthus spp.) seedling emergence in different tillage systems. Weed Sci.
45:684-690.

Roberts, HA. 1984. Crop and weed emergence patterns in relation to time of cultivation
and rainfall. Ann. Appl. Biol. 105:263-275.

Salisbury, F. B. and C. w. Ross. 1992. Pages 451-456, 485-497 in Plant physiology. 4‘h
ed. Belmont, CA: Wadsworth. ,

 

Taiz, L. and E. Zeiger. 1998. Pages 486, 496-498, 677 in Plant physiology. 2“d ed.
Sunderland, MA: Sinauer Associates.

Wesson, G. and PF. Wareing. 1969. The induction of light sensitivity in weed seeds by
burial. J. Exp. Bot. 202414-425.

Wiese, AM. and L.K. Binning. 1987. Calculating the threshold temperature of
development for weeds. Weed Sci. 35:177-179.

Weed Science Society of America, 1994, Pages 147-152 in Herbicide Handbook, 7th ed.

99

Table 15 -— Description of cultivation treatments and timings in 1998 and 1999.

 

 

Treatment Description Timing 1998 1999
No Cultivation None N/A N/A
One cultivation prior to the ﬁrst glufosinate rd m
. . A June 3 June 4
application. t“
One cultivation one week after the second m m 'L-. _
. . _ B June 25 June 30
glufosrnate application.
One cultivation one week after the ﬁnal m rd
. . _ C July 17 July 23
glufosrnate application.
Two cultivations; once prior to the first m m
. . . June 3 June 4
glufosrnate application and one week after A + B m m
. _ _ & June 25 & June 30
the second glufosrnate application.
Two cultivations; once prior to the ﬁrst A C June 3'“ June 4th
+
glufosinate application and one week after & July 17th & July 23'‘1

the ﬁnal glufosinate application.

 

 

 

 

100

Figure 10 — Effect of cultivation timing on the emergence of annual weeds in glufosinate
resistant sugarbeet in 1998. (Error bars represent differences at the 0.05 levels)

101

 
     

 

 

 

 

 

 

 

 

 

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105

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Appendices

115

Table 16 - Yield3 and control of common lambsquarters, redroot pigweed, and
velvetleafb with pyrazon, ethoﬁlmesate, or cycloate followed by postemergence
applications of glyphosatec to sugarbeet at the Michigan Sugar Co. site in 1998.

 

 

 

-- Program-u Rate Applied ---- °/o Control ---- Yield --Recov. Sugarau Cost°
# Herbicide Kg/ha Date Colq Rrpw Vele Ma 13qu Kﬂia $lha
1 None NIA N/A 0 O 0 20.6 88 1821 b $ 0
2 Glyt 0.63 5/21 98 87 98 50.7 91 4614 a $ 55
Glyt 0.63 6/22
3 Cycl 4.48 5/6 100 99 100 57.4 95 5442 a S 155
Glyt 0.63 5/21
Glyt 0.63 6/22
4 Pyzn 5.04 5/6 100 99 100 56.5 93 5286 a $ 410
Cycl 4.48 5/6
Glyt 0.63 5/21
Glyt 0.63 6/22
5 Pyzn 5.04 SIG 96 96 98 50.9 94 4790 a $ 305
Glyt 0.63 5/21
Glyt 0.63 6/22
6 Pyzn 2.52 5/6 97 92 96 53.0 95 5019 a $ 180
Glyt 0.63 5/21
Glyt 0.63 6/22
7 Etho 2.24 5/6 98 100 100 57.7 91 5233 a $ 540
Pyzn 5.04 5/6
Glyt 0.63 5/21
Glyt 0.63 6/22
8 Etho 1.12 5/6 97 95 99 54.7 89 4853 a $ 300
Pyzn 2.52 5/6
Glyt 0.63 5/21
Glyt 0.63 6/22
LSDOIOS 4.1 13.5 4.6 16.3 N/S
CV% 3.2 11.1 3.7 22.2 8.8

 

'Yield represents the weight of sugarbeet root from the ﬁeld in Mg/ha on October 5, 1998.

bWeed control rated July 27, 1998. Colq — common lambsquarters, Rrpw - redroot pigweed,

Vele - velvetleaf

cCycl - cycloate, Etho — ethofumesate, Glyt — glyphosate, Pyzn — pyrazon

dRecoverable sugar is the amount of white sugar that can be obtained from the processing of sugarbeet

roots, and is calculated using the yield, percent sucrose in the beet, and approximate purity of the juice.

“'All prices in the tables reﬂect the cost of product, fuel, maintenance, repair, and labor associated with

broadcast application of each herbicide program. Prices only reﬂect Operating costs and do not include the
cost of purchasing, owning, or storing equipment.

116

 

Table 17 - Yield'l and control of common lambsquarters, redroot pigweed, and
velvetleafb with pyrazon, ethofumesate, or cycloate followed by postemergence
applications of glufosinatec to sugarbeet at the Michigan Sugar Co. site in 1998.

 

 

.- Programm Rate Applied ---- % Control ---- Yield Recov. Sugar“ Cost°
# Herbicide Kglha Date Colq Rrpw Vele Mg/ha Kg/T lgg/ha $Iha
1 None NIA NIA o o o 13.7 112 1537 c s o
2 Gluf 0.29 5/12 88 94 100 46.9 110 5156 ab $140

Gluf 0.29 6/5
Gluf 0.4 6/1 5

3 Cycl 4.48 4/28 82 97 100 43.1 109 4695 b $ 245
Gluf 0.29 5/21
Gluf 0.29 5/27
Gluf 0.4 6/1 5

4 Cycl 4.48 4/28 93 100 100 52.5 113 5942 a $ 495
Pyzn 5.04 4/28
Gluf 0.29 5/21
Gluf 0.29 5/27
Gluf 0.4 6/1 5

5 Pyzn 5.04 4/28 76 95 100 41.5 113 4691 b $ 390
Gluf 0.29 5/21
Gluf 0.29 5/27
Gluf 0.4 6/15

6 Pyzn 2.52 4/28 78 98 100 42.2 111 4697 b $ 265
Gluf 0.29 5/21
Gluf 0.29 5/27
Gluf 0.4 6/1 5

7 Etho 2.24 4/28 91 97 100 44.2 113 5003 ab $ 585
Pyzn 5.04 4/28
6qu 0.29 5/21
Gluf 0.29 5/27
Gluf 0.4 6/1 5

8 Etho 1.12 4/28 80 100 100 47.4 1 13 5373 ab 3 365
Pyzn 2.52 4/28
Gluf 0.29 5/21
Gluf 0.29 5/27
Gluf 0.4 6/1 5

L800” 16.9 5 - 9.2 N/S
CV% 15.7 4.1 - 15.3 4.1
'Yield represents the weight of sugarbeet root from the ﬁeld in Mg/ha harvested October 5, 1998.

 

 

I’Weed control rated July 27, 1998. Colq - common 1amsquarters, Rrpw — redroot pigweed,
Vele - velvetleaf

cCycl — cycloate, Etho — ethofumesate, Gluf - glufosinate, Pyzn - pyrazon

dRecoverable sugar is the amount of white sugar that can be obtained from the processing of sugarbeet
roots, and is calculated using the yield, percent sucrose in the beet, and approximate purity of the juice.

cAll prices in the tables reﬂect the cost of product, fuel, maintenance, repair, and labor associated with

broadcast application of each herbicide program. Prices only reﬂect operating costs and do not include the
cost of purchasing, owning, or storing equipment.

117

Table 18 — Yield“ and controlb of common lambsquarters and redroot pigweed with
pyrazon or ethofumesate followed by postemergence applications of glyphosatec to
sugarbeet at the Monitor Sugar Co. site in 1998.

 

-- Program-- Rate Applied % Weed Control Yield Recov. Sugar" Cost°
# Herbicide Kg/ha Date Colq Rrpw T/ha Kg/T Kglha $lha

 

1 None NIA NIA 0 0 25.8 119 3062 b $ 0

2 Glyt 0.63 5/19 90 97 52.7 116 6104 a $ 55
Glyt 0.63 6/4

3 Etho 1.68 5/8 93 100 51.4 119 6111 a $ 235

Glyt 0.63 5/19
Glyt 0.63 6/4

4 Etho 0.84 5/8 83 95 49.8 118 5901a $145
Glyt 0.63 5/19
Glyt 0.63 6/4

5 Pyzn 4.48 518 94 100 48.3 113 5460a $285
Glyt 0.63 5/19
Glyt 0.63 6/4

6 Pyzn 2.24 5/8 91 97 56.5 115 6477a $170
Glyt 0.63 5/19
Glyt 0.63 6/4

7 Pyzn 1.68 5/8 95 95 54.4 120 6509a $350
Etho 1.68 5/8
Glyt 0.63 5/19
Glyt 0.63 6/4

8 Pyzn 1.68 5/8 90 100 51.6 118 6107a $240
Etho 0.84 5/8
Glyt 0.63 5/19
Glyt 0.63 6/4

9 Hand-weed N/A NIA 100 100 52.3 120 6256 a -

 

 

LSDo.05 8.5 6.2 9.3 N/S
CV% 7.1 4.87 12.9 5.4

 

'Yield represents the weight of sugarbeet root from the ﬁeld in Mg/ha harvested October 9, 1998.
bWeed control rated July 9, 1998. Colq - common lambsquarters, Rrpw — redroot pigweed
cCycl — cycloate, Etho — ethofumesate, Glyt — glyphosate, Pyzn - pyrazon

“Recoverable sugar is the amount of white sugar that can be obtained from the processing of sugarbeet
roots, and is calculated using the yield, percent sucrose in the beet, and approximate purity of the juice.

eAll prices in the tables reﬂect the cost of product, fuel, maintenance, repair, and labor associated with

broadcast application of each herbicide program. Prices only reﬂect operating costs and do not include the
cost of purchasing, owning, or storing equipment.

118

Table 19 — Yield‘1 and control of common lambsquarters and redroot pigweedb with
pyrazon or ethofumesate followed by postemergence applications of glufosinate or

desmedipham and phenmedipham plus triflusulfuron plus clopyralidc to sugarbeet at the

Monitor Sugar Co. site in 1998.

 

 

Program ----- Rate Applied %Weed Control Yield Recov. Sugar“ Cost°

# Herbicide Ktha Date Colq Rrpw T/ha KQ/T Kg/ha $lha

1 None N/A N/A 0 0 24.0 126 3021 b $ 0

2 Gluf 0.29 5/19 88 98 45.1 128 5755a $85
Gluf 0.29 6/4

3 Etho 1.68 5/8 92 100 51.6 126 6498a $265
Gluf 0.29 5/19
Gluf 0.29 6/4

4 Etho 0.84 5/8 94 97 49.2 127 6242a $175
Gluf 0.29 5/19
Gluf 0.29 6/4

5 Pyzn 4.48 5/8 92 94 51.6 124 6374a $315
Gluf 0.29 5/19
Gluf 0.29 6/4

6 Pyzn 2.24 5/8 93 98 48.9 124 6064a $200
Gluf 0.29 5/19
Gluf 0.29 6/4

7 Pyzn 1.68 5/8 89 99 48.7 124 6049a $380
Etho 1.68 5/8
6qu 0.29 5/19
Gluf 0.29 6/4

8 Pyzn 1.68 5/8 89 99 56.8 131 7464 a $290
Etho 0.84 5/8
Gluf 0.29 5/19
Gluf 0.29 6/4

9 Desm&phen 0.56 5/15 86 99 43.4 125 54358 $350
Tfsu 0.0174 5/15
Desm&phen 0.56 6/1
Tfsu 0.0174 6/1
Clpy 0.105 6/1

10 Etho 1.68 5/8 87 94 47.4 127 6003a $535
Desm&phen 0.56 5/1 5
Tfsu 0.0174 5/15
Desm&phen 0.56 6/1
Tfsu 0.0174 6/1
Clpy 0.105 6/1

11 Pyzn 4.48 5/8 92 98 47.2 128 6026a $585
Desm&phen 0.56 5/15
Tfsu 0.0174 5/15
Desm&phen 0.56 6/1
Tfsu 0.0174 6/1
Clyp 0.105 6/1

119

 

12 Pyzn 3.36 5/8 93 96 47.8 131 6242 a $ 710
Etho 1 .68 5/8
Desm&phen 0.56 5/15
Tfsu 0.0174 5/15
Desm&phen 0.56 6/1
Tfsu 0.0174 6/1
Clpy 0.105 6/1
LSD0_05 13 6.1 14.0 N/S
CV% 10.8 4.75 20.7 4.4

 

'Yield represents the weight of sugarbeet root from the ﬁeld in Mg/ha.harvested October 9, 1998.

l'Weed control was rated July 9, 1998. Colq — common lambsquarters, Rrpw -— redroot pigweed

°Clpy — clopyralid, Cycl — cycloate, Desm&phen - desmedipham and phenmedipham, Etho — ethofumesate,
Gluf - glufosinate, Pyzn — pyrazon, Tfsu - triﬂusulfuron

“Recoverable sugar is the amount of white sugar that can be obtained from the processing of sugarbeet
roots, and is calculated using the yield, percent sucrose in the beet, and approximate purity of the juice.

‘All prices in the tables reﬂect the cost of product, fuel, maintenance, repair, and labor associated with
broadcast application of each herbicide program Prices only reﬂect operating costs and do not include the
cost of purchasing, owning, or storing equipment.

120

 

Table 20 — Control of common lambsquarters, redroot pigweed, and Pennsylvania
smartweeda in glyphosate resistant sugarbeet at the Saginaw Valley Bean & Beet Farm in
1 998.

 

 

 

---- Program---- Rate Applied ~--------- % Control Costc
# Herbicideb Kg/ha Date Colq Rrpw Pesw WM
1 None NIA N/A 0 0 0 $ 0
2 Glyt 0.63 6/11/98 100 100 100 5 55
Glyt 0.63 6/25/98

3 Etho 1.68 5/1 1/98 100 100 100 $ 235
Glyt 0.63 6/1 1/98
Glyt 0.63 6/25/98

4 Etho 0.84 5/11/98 96 100 100 $ 145
Glyt 0.63 6/1 1/98
Glyt 0.63 6/25/98

5 Pyzn 4.48 5/11/98 100 100 100 $ 285
Glyt 0.63 6/1 1/98
Glyt 0.63 6/25/98

6 Pyzn 2.24 5/11/98 97.5 100 100 $ 170
Glyt 0.63 6/1 1/98
Glyt 0.63 6/25/98

7 Pyzn 3.36 5/11/98 100 100 100 $ 410
Etho 1.68 5/11/98
Glyt 0.63 6/1 1/98
Glyt 0.63 6/25/98

8 Pyzn 1.68 5/11/98 100 100 100 $ 235
Etho 0.84 5/1 1/98
Glyt 0.63 6/1 1/98
Glyt 0.63 6/25/98

9 Cycl 3.36 5/11/98 95 97.5 100 $ 160
Glyt 0.63 6/11/98
Glyt 0.63 6/25/98

10 Desm&Phen 0.56 6/1 1/98 100 97.5 82.5 $ 350
Tfsu 0.0174 6/11/98
Desm&Phen 0.56 6/17/98
Tfsu 0.01 74 6/1 7/98
Clpy 0.105 6/17/98

11 Etho 1.68 5/11/98 92.5 95 100 $ 535
Desm&Phen 0.56 6/1 1/98
Tfsu 0.0174 6/1 1/98
Desm&Phen 0.56 6/17/98
Tfsu 0.0174 6/17/98
Clpy 0.105 6/17/98

12 Pyzn 4.48 5/1 1/98 100 100 95 $ 585
Desm&Phen 0.56 6/1 1/98
Tfsu 0.0174 6/11/98
Desm&Phen 0.56 6/1 7/98
Tfsu 0.0174 6/17/98
Clpy 0.105 6/17/98

121

13 Pyzn 3.36 5/11/98 82.5 92.5 85 $ 710

Etho 1 .68 5/1 1/98
Desm&Phen 0.56 6/1 1/98
Tfsu 0.0174 6/1 1/98

Desm&Phen 0.56 6/1 7/98
Triﬂusulfuron 0.0174 6/17/98

14 Cycl 3.36 5/11/98 100 100 95 $ 460
Desm&Phen 0.56 6/1 1/98
Tfsu 0.0174 6/1 1/98
Clpy 0.105 6/17/98

Desm&Phen 0.56 6/17/98

Triﬂusulfuron 0.0174 6/1 7/98
LSDoos 9.5 7.3 13.1
CV% 4.9 3.7 6.9

Wood control was rated July 27, 1998. Colq — common lambsquarters, Rrpw - redroot pigweed,
Pesw — Pennsylvania smartweed

l’Clpy — clopyralid, Cycl - cycloate, Desm&phen — desmedipham and phenmedipham, Etho -
ethofumesate, Glyt - glyphosate, Pyzn — pyrazon, Tfsu - triﬂusulfuron

“All prices in the tables reﬂect the cost of product, fuel, maintenance, repair, and labor associated with

broadcast application of each herbicide program Prices only reﬂect operating costs and do not include the
cost of purchasing, owning, or storing equipment.

122

Table 21 — Control of common lambsquarters, redroot pigweed, velvetleaf, and
Pennsylvania smartweed“ in glufosinate resistant sugarbeet at the Saginaw Valley Bean &
Beet Farm in 1998.

 

 

----- Program----- Rate Applied ------- °/o Weed Control ----- Costc
# Herbicideb Kl/ha Date Colq Rrpw Vele Pesw $1118
1 None N/A NIA 0 0 0 0 $ 0
2 Gluf 0.29 5/19/98 67 92 100 92 $ 85
Gluf 0.29 6/4/98
3 Etho 1.68 4/27/98 91 100 90 100 $ 265
Gluf 0.29 5/19/98
Gluf 0.29 6/4/98
4 Etho 0.84 4/27/98 91 100 100 92 $ 175
Gluf 0.29 5/1 9/98
Gluf 0.29 6/4/98
5 Pyzn 4.48 4/27/98 95 97 97 100 $ 315
Gluf 0.29 5/22/98
Gluf 0.29 6/1 1/98
6 Pyzn 2.24 4/27/98 91 100 97 100 $ 200
Gluf 0.29 5/19/98
Gluf 0.29 6/4/98
7 Pyzn 3.36 4/27/98 100 100 97 100 $ 440
Etho 1.68 4/27/98
Gluf 0.29 5/22/98
Gluf 0.29 6/1 1/98
8 Pyzn 1.68 4/27/98 100 92 99 100 $ 265
Etho 0.84 4/27/98
Gluf 0.29 5/19/98
Gluf 0.29 6/1 1/98
9 Cycl 3.36 4/27/98 96 100 100 98 $ 190
6qu 0.29 5/22/98
Gluf 0.29 6/1 1/98
10 Desm&Phen 0.56 5/15/98 92 100 85 85 $ 350

Tfsu 0.0174 5/15/98
Desm&Phen 0.56 5/22/98
Tfsu 0.0174 5/22/98
Clpy 0.105 5/22/98
11 Etho 1.68 4/27/98 100 100 87 100 $ 535
Desm&Phen 0.56 5/15/98
Tfsu 0.0174 5/15/98
Desm&Phen 0.56 5/22/98
Tfsu 0.0174 5/22/98
Clpy 0.105 5/22/98

123

 

12 Pyzn 4.48 4/27/98 100 100 80 90 $ 585
Desm&Phen 0.56 511 5198
Tfsu 0.0174 511 5198
Desm&Phen 0.56 5/22/98
Tfsu 0.0174 5122/98
Clpy 0.105 5122198
13 Pyzn 3.36 4127/98 100 100 78 100 $ 710
Etho 1 .68 4/27/98
Desm&Phen 0.56 5/1 5198
Tfsu 0.0174 511 5/98
Desm&Phen 0.56 5122198
Tfsu 0.0174 5122198
Clpy 0.105 5122198
14 Cycl 3.36 4127198 100 100 100 100 $ 460
Desm&Phen 0.56 5/1 5198
Tfsu 0.01 74 5/1 5198
Clpy 0.105 5122198
Desm&Phen 0.56 5122198
Tfsu 0.01 74 5122198
LSDoos 6.9 8.5 18.5 12.7
CV% 3.7 4.3 10 6.7

 

 

‘Weed control was rated July 9, 1998. Colq — common lambsquarters, Rrpw — redroot pigweed

l’Clpy — clopyralid, Cycl — cycloate, Desm&phen - desmedipham and phenmedipham, Etho —
ethofumesate,
Gluf - glufosinate, Pyzn — pyrazon, Tfsu - triﬂusulfuron

cAll prices in the tables reﬂect the cost of product, fuel, maintenance, repair, and labor associated with

broadcast application of each herbicide program. Prices only reﬂect operating costs and do not include the
cost of purchasing, owning, or storing equipment.

124

Table 22 — Sugarbeet injury“, yield“, and control of common lambsquarters and redroot
pigweedc with pyrazon, ethofumesate, or cycloate followed by postemergence
applications of glyphosate or desmedipham and phenmedipham plus triﬂusulfuron plus
clopyralidd to sugarbeet at the Michigan Sugar Co. site in 1999.

 

 

 

 

-- Program-m Rate Applied Injury % Control --- Yield Recov. Sugar“ Cos?r
# Herbicide kg/ha Date % Colq Rrpw Vele T/ha kg/T kg/ha $/ha
1 None NIA NIA 3 0 0 0 35.0 131 4538 d 5 0
2 Glyt 0.63 5/19 3 100 100 100 49.2 126 6202 a-c $ 55
Glyt 0.63 6118
3 Cycl 4.48 4/30 7 92 91 100 48.3 129 6223 a-c $ 270
Glyt 0.63 5119
Glyt 0.63 6/18
4 Cycl 4.48 4/30 6 98 98 100 47.7 132 6289 a-c $ 550
Pyzn 5.04 511 .
Glyt 0.63 5119 I
Glyt 0.63 6118
Glyt 0.63 7113
5 Cycl 2.24 4130 4 98 91 100 46.8 131 6128 a—c $190
Glyt 0.63 5119
Glyt 0.63 6118
Glyt 0.63 7113
6 Cycl 2.24 4/13 6 100 100 100 47.8 127 6062 a-c $315
Pyzn 2.52 5/1
Glyt 0.63 5119
Glyt 0.63 6118
Glyt 0.63 7113
7 Pyzn 5.04 5/1 6 100 100 100 48.2 132 6352 a-c $ 330
Glyt 0.63 5119
Glyt 0.63 6/18
Glyt 0.63 7113
8 Pyzn 2.52 5/1 6 100 100 99 49.7 131 6459 ab 3 205
Glyt 0.63 5119
Glyt 0.63 6118
Glyt 0.63 7113
9 Etho 2.24 5/1 5 99 100 100 56.6 127 7050 a $ 545
Pyzn 5.04 5/1
Glyt 0.63 5119
Glyt 0.63 6/18
10 Etho 1.12 5/1 5 85 89 100 52.1 125 6522 ab 5 300
Pyzn 2.52 511
Glyt 0.63 5119
Glyt 0.63 6118
11 Glyt 0.63 5/19 3 76 79 87 47.8 128 6041 a-c $ 305
Glyt 0.63 6118
Pyzn 5.04 6118

125

12 Desm&Phen 0.56 5119 29 76 76 100 43.5 124 5367 b-d $ 355
Tfsu 0.0174 5119
Desm&Phen 0.56 5127
Tfsu 0.01 74 5/27
Clpy 0.105 5127

13 Cycl 4.48 4/30 32 90 91 100 44.7 123 5450 b-d $455
Desm&Phen 0.56 5/19
Tfsu 0.0174 5119
Desm&Phen 0.56 5127
Tfsu 0.0174 5127
Clpy 0.105 5127

14 Cycl 4.48 4/30 32 95 91 93 43.7 122 5329 b—d $ 705
Pyzn 5.04 5/1
Desm&Phen 0.56 5119
Tfsu 0.0174 5119
Desm&Phen 0.56 5127
Tfsu 0.0174 5127
Clpy 0.105 5127

15 Pyzn 5.04 511 34 85 81 86 41.2 124 5056od $605
Desm&Phen 0.56 5/19
Tfsu 0.0174 5/19
Desm&Phen 0.56 5/27
Tfsu 0.0174 5/27
Clpy 0.105 5127

16 Pyzn 5.04 511 38 85 90 87 37.1 120 4419d $845
Etho 2.24 511
Desm&Phen 0.56 5/19
Tfsu 0.0174 5119
Desm&Phen 0.56 5127
Tfsu 0.0174 5127
Clpy 0.105 5127

 

LSDo_05 10 16.2 16.9 14.2 12.6 N/S
CV% 51.3 13.1 13.7 11 19.1 5.24

 

“Injury was recorded on June 11, 1999.
“Yield represents the weight of sugarbeet root from the ﬁeld in Mg/ha.harvested October 5, 1998.
cWeed control was rated July 20, 1999. Colq — common lambsquarters, Rrpw — redroot pigweed

“Clpy — clopyralid, Cycl — cycloate, Desm&phen — desmedipham and phenmedipham, Etho —
ethofumesate, Glyt - glyfosate, Pyzn — pyrazon, Tfsu - triﬂusulfuron

“Recoverable sugar is the amount of white sugar that can be obtained from the processing of sugarbeet
roots, and is calculated using the yield, percent sucrose in the beet, and approximate purity of the juice.

fAll prices in the tables reﬂect the cost of product, fuel, maintenance, repair, and labor associated with

broadcast application of each herbicide program. Prices only reﬂect operating costs and do not include the
cost of purchasing, owning, or storing equipment.

126

 

Table 23 — Sugarbeet injury“, yield“, and control of common lambsquarters and redroot
pigweedc with pyrazon, ethofumesate, or cycloate followed by postemergence

applications of glufosinate or desmedipham and phenmedipham plus triﬂusulfuron plus
clopyralid“ to sugarbeet at the Michigan Sugar Co. site in 1999.

 

 

--- Program-- Rate Applied Injury --- "/6 Control ---- Yield Recov. Sugar“ CostT
# Herbicide kg/ha Date % Colq Rrpw Vele 'l'lha kgfl' kg/ha $/ha
1 None NIA N/A 1 0 0 0 42.0 126 5307 e 5 0
2 Gluf 0.4 5/19 5 98 89 100 62.2 123 7673 ab 5 170
Gluf 0.4 6/10
Gluf 0.4 6/18

3 Gluf 0.4 5/19 0 95 90 93 57.6 126 7245 a—c 5 115
Gluf 0.4 6/10

4 Cycl 4.48 4/30 1 100 82 100 61.4 122 7469 a 5 215
Gluf 0.4 5/19
Gluf 0.4 6/18

5 Cycl 4.48 4/30 3 100 98 100 56.8 124 7015 a-d $ 470
Pyzn 5.04 511
Gluf 0.4 5/19
Gluf 0.4 6/18
Gluf 0.4 7/13

6 Cycl 2.24 4/30 3 100 97 100 60.5 122 7355 ab 5 220
Gluf 0.4 5/19
Gluf 0.4 6/18
Gluf 0.4 7/13

7 Cycl 2.24 4/13 1 99 96 97 57.6 127 7308 ab 5 320
Pyzn 2.52 5/1
Gluf 0.4 5/19
Gluf 0.4 6/10
Gluf 0.4 7/13

8 Pyzn 5.04 5/1 1 100 100 99 61.4 131 8049 a 5 420
Gluf 0.4 5/19
Gluf 0.4 6/10
Gluf 0.4 7/13

9 Pyzn 2.52 5/1 0 100 100 100 62.6 127 7935 a $ 295
Gluf 0.4 5/19
Gluf 0.4 6/10
Gluf 0.4 7/13

10 Etho 2.24 5/1 6 98 90 100 54.1 126 6780 a-d $ 605
Pyzn 5.04 5/1
Gluf 0.4 5/19
Gluf 0.4 6/18

11 Etho 1.12 5/1 6 100 81 100 57.1 127 7249 a-c $ 360
Pyzn 2.52 5/1
Gluf 0.4 5/19
Gluf 0.4 6/1 8

127

12 Desm&Phen 0.56 5119 13 46 47 62 45.5 124 5765 de $ 350
Tfsu 0.0174 5119
Desm&Phen 0.56 5127
Tfsu 0.0174 5127
Clpy 0.105 5127
13 Cycl 4.48 4/30 20 92 79 90 52.9 129 6803 a-d $ 455
Desm&Phen 0.56 5119
Tfsu 0.0174 5119
Desm&Phen 0.56 5127
Tfsu 0.01 74 5/27
Clpy 0.105 5127
14 Cycl 4.48 4130 20 95 90 80 53.1 123 6678 a~e $ 705
Pyzn 5.04 5/1
Desm&Phen 0.56 5119 5
Tfsu 0.0174 5/19 :
Desm&Phen 0.56 5127
Tfsu 0.0174 5127
Clpy 0.105 5127
15 Pyzn 5.04 511 12 81 78 87 47.1 124 ~ 5895 c-e $ 605
Desm&Phen 0.56 5/19
Tfsu 0.0174 5119
Desm&Phen 0.56 5127
Tfsu 0.0174 5127
Clpy 0.105 5127
16 Pyzn 5.04 5/1 20 93 85 82 51.0 123 6295 b-e $ 845
Etho 2.24 511
Desm&Phen 0.56 5119
Tfsu 0.0174 5119
Desm&Phen 0.56 5127
Tfsu 0.0174 5127
Clpy 0.105 5127

 

 

LSDogs 9.3 18.2 17 24.4 10.9 NIS
CV% 94.3 14.5 14.6 19.6 13.8 5.8

 

“Injury was recorded on June 11, 1999.
I’Yield represents the weight of sugarbeet root from the field in Mg/ha.harvested October S, 1998.
Weed control was rated July 20, 1999. Colq - common lambsquarters, Rrpw — redroot pigweed

“Clpy - clopyralid, Cycl — cycloate, Desm&phen — desmedipham and phenmedipham, Etho —
ethofumesate, Gluf — glufosinate, Pyzn — pyrazon, Tfsu - triﬂusulfuron

cRecoverable sugar is the amount of white sugar that can be obtained from the processing of sugarbeet
roots, and is calculated using the yield, percent sucrose in the beet, and approximate purity of the juice.

fAll prices in the tables reﬂect the cost of product, fuel, maintenance, repair, and labor associated with

broadcast application of each herbicide program. Prices only reﬂect operating costs and do not include the
cost of purchasing, owning, or storing equipment.

128

Table 24 — Sugarbeet injury“ and control of annual grass, common lambsquarters, and
redroot pigweedb with ethofumesate or pyrazon followed by glyphosate or desmedipham
and phenmedipham plus triﬂusulfuron plus clopyralidc in sugarbeet at Monitor Sugar Co.
site in 1999.

 

 

---- Program-m Rate Applied Injury ------ % Control ----- Costd
# Herbicide kglha Date "/6 ANGR Colq Rrpw $lha
1 None N/A N/A 1 0 0 0 $ 0
2 Glyt 0.63 5/28 3 100 100 100 $ 80
Glyt 0.63 6/ 10
Glyt 0.63 719
3 Glyt 0.63 5/28 2 97 97 92 $ 55
Glyt 0.63 6110
4 Desm&phen 0.56 5120 24 44 89 80 $ 350

Tfsu 0.01 74 5120
Desm&phen 0.56 6/3
Tfsu 0.0174 613
Clpy 0.105 6/3

5 Pyzn 4.48 514 4 99 99 100 $ 285
Glyt 0.63 5128
Glyt 0.63 6123

6 Pyzn 2.24 514 4 97 99 99 $170
Glyt 0.63 5/28
Glyt 0.63 6110

7 Pyzn 4.48 514 17 51 97 94 $ 585

Desm&phen 0.56 5120
Tfsu 0.01 74 5120
Desm&phen 0.56 6/3
Tfsu 0.0174 613
Clpy 0.105 613

8 Etho 1.68 514 4 100 100 100 $295
Glyt 0.63 6/3
Glyt 0.63 6123

9 Etho 1.68 514 22 96 98 100 $ 535

Desm&phen 0.56 5/20
Tfsu 0.01 74 5/20
Desm&phen 0.56 613
Tfsu 0.0174 613
Clpy 0.105 6/3

10 Pyzn 3.36 514 1 100 99 100 $410
Etho 1.68 514
Glyt 0.63 6/3
Glyt 0.63 6123

11 Pyzn 1.68 514 6 100 98 100 $235
Etho 0.84 514
Glyt 0.63 6/3
Glyt 0.63 6123

129

12 Pyzn 3.36 5/4 19 89 97 97 $ 710
Etho 1.68 514
Desm&phen 0.56 5120
Tfsu 0.01 74 5120
Desm&phen 0.56 6/3
Tfsu 0.01 74 613
Clpy 0.105 6/3
LSDogs 3.7 14.3 7.3 7.3
CV % 28.2 12.2 5.6 5.7

“Injury was recorded on June 11, 1999.

t'Weed control was rated July 20, I999. Angr -— annual grass, Colq - common lambsquarters,
Rrpw — redroot pigweed

“Clpy — clopyralid, Desm&phen — desmedipham and phenmedipham, Etho — ethofumesate, Glyt -
glyfosate, Pyzn — pyrazon, Tfsu - triﬂusulfuron

 

“All prices in the tables reﬂect the cost of product, fuel, maintenance, repair, and labor associated with

broadcast application of each herbicide program. Prices only reﬂect operating costs and do not include the
cost of purchasing, owning, or storing equipment.

130

Table 25 — Sugarbeet injury“, yield“, and control of annual grass, common lambsquarters
and redroot pigweedc with ethofumesate or pyrazon followed by postemergence
applications of glufosinate or desmedipham and phenmedipham plus triﬂusulfuron plus
clopyralidd to sugarbeet at the Monitor Sugar Co. site in 1999.

 

 

--- Program-m Rate Applied Injury ---- % Control --- Yield Sugar“ Costr
# Herbicide kg/ha Date % ANGR Colq Rrpw T/ha kgﬂa WM
1 None N/A N/A 1 0 0 0 35.0 4583 b $ 0
2 Gluf 0.4 5128 0 100 98 100 55.0 7054 a $ 170
Gluf 0.4 6110
Gluf 0.4 7/9
3 Gluf 0.4 5128 1 97 94 96 54.8 7127 a $ 115
Gluf 0.4 6/10
4 Desm&phen 0.56 5/20 10 51 80 94 51.6 6618 a $ 350

Tfsu 0.01 74 5120
Desm&phen 0.56 613
Tfsu 0.01 74 6/3
Clpy 0.105 6/3

5 Pyzn 4.48 5/4 0 99 96 99 56.8 7413a $345
Gluf 0.4 5/28
Gluf 0.4 6/23

6 Pyzn 2.24 5/4 0 97 98 98 53.0 6605a $205
Gluf 0.4 5/28
Gluf 0.4 6/10

7 Pyzn 4.48 5/4 13 79 94 92 53.5 66983 $585

Desm&phen 0.56 5120
Tfsu 0.01 74 5120
Desm&phen 0.56 613
Tfsu 0.0174 613
Clpy 0.105 6/3

8 Etho 1.68 5/4 3 99 99 100 59.5 7730 a $ 295
Gluf 0.4 6/3
Gluf 0.4 6/23

9 Etho 1.68 5/4 11 89 100 100 50.6 6479 ab $ 535

Desm&phen 0.56 5120
Tfsu 0.0174 5120
Desm&phen 0.56 613
Tfsu 0.01 74 6/3
Clpy 0.105 6/3

10 Pyzn 3.36 5/4 0 97 99 100 52.4 6967 a $ 470
Etho 1.68 5/4
Gluf 0.4 6/3
Gluf 0.4 6/23

11 Pyzn 1.68 5/4 3 99 99 100 53.7 7106 a $ 295
Etho 0.84 5/4
Gluf 0.4 6/3

Gluf 0.4 6/23

131

mm 12 Pyzn 3.36 514 12 92 100 100 56.4 6447 ab $710
Etho 1.68 514
plus Desm&phen 0.56 5/20
Tfsu 0.0174 5120
Desm&phen 0.56 6/3
Tfsu 0.0174 613
Clpy 0.105 613
L800,“ 3.3 19.7 6.8 7.8 5.0
CV% 51.2 16.3 5.3 6.0 6.9

 

 

“Injury was recorded on June 11, 1999.
“Yield represents the weight of sugarbeet root from the ﬁeld in Mg/ha.harvested October 15, 1999. 1

“Weed control was rated July 20, I999. Angr -— annual grass, Colq - common lambsquaners,
Rrpw - redroot pigweed

“Clpy -— clopyralid, Desm&phen - desmedipham and phenmedipham, Etho - ethofumesate,
Gluf — glufosinate, Pyzn — pyrazon, Tfsu - triﬂusulfuron ' "t

 

“Recoverable sugar is the amount of white sugar that can be obtained from the processing of sugarbeet
roots, and is calculated using the yield, percent sucrose in the beet, and approximate purity of the juice.

fAll prices in the tables reﬂect the cost of product, fuel, maintenance, repair, and labor associated with

broadcast application of each herbicide program. Prices only reﬂect operating costs and do not include the
cost of purchasing, owning, or storing equipment.

132

 

Table 26 — Sugarbeet injury“, yield“, and control of common lambsquarters and redroot
pigweedc with pyrazon, ethofumesate, or cycloate followed by postemergence
applications of glyphosate or desmedipham and phenmedipham plus triﬂusulfuron plus
clopyralid“ to sugarbeet at the Saginaw Valley Bean and Beet Farm in 1999.

 

 

---- Program----- Rate Applied Injury % Weed Control Yield Recov. Sugar“ CosT
# Herbicide kg/ha Date % Colq Rrpw T/ha kng Kg/ha ME
1 None N/A N/A 0 0 0 51.9 117 5841 f $ 0
2 Glyt 0.63 5127 0 100 100 79.3 115 9128 a-d $ 80

Glyt 0.63 6117
Glyt 0.63 717
3 Glyt 0.63 5/27 1 100 100 85.5 116 9952 ab 5 55
Glyt 0.63 6/17
4 Desm&phen 0.56 5119 19 52 79 77.3 115 8858 b—e $ 350
Tfsu 0.0174 5/19
Desm&phen 0.56 614
Tfsu 0.0174 6/4
Clpy 0.105 614
5 Pyzn 4.48 4/28 4 100 100 80.6 117 9444 a—d $ 285
Glyt 0.63 5/27
Glyt 0.63 6/17
6 Pyzn 2.24 4128 6 100 100 76.7 117 8984 a-e $ 170
Glyt 0.63 5127
Glyt 0.63 6/17
7 Pyzn 4.48 4/28 21 100 100 69.8 113 7899 9 $ 585
Desm&phen 0.56 5/1 9
Tfsu 0.0174 5/19
Desm&phen 0.56 6/4
Tfsu 0.01 74 614
Clpy 0.105 6/4
8 Etho 1.68 4/28 1 100 100 77.7 116 8992 a-e $ 235
Glyt 0.63 6/1
Glyt 0.63 6/24
9 Etho 0.84 4/28 3 100 100 81.1 117 9484 a-c $ 145
Glyt 0.63 611
Glyt 0.63 6124
10 Etho 1.68 4/28 24 100 100 74.3 1 17 8681 c-e $ 535
Desm&phen 0.56 5119
Tfsu 0.0174 5/19
Desm&phen 0.56 614
Tfsu 0.0174 614
Clpy 0.105 6/4
11 Pyzn 3.36 4/28 0 100 100 78.7 116 9111 a—d $ 410
Etho 1.68 4/28
Glyt 0.63 6/1
Glyt 0.63 6124

133

001

S350

S235

5170

3585

s 235

5145

12 Pyzn 1.68 4/28 4 100 100 86.9 117 10171 a $235
Etho 0.84 4/28

Glyt 0.63 611
Glyt 0.63 6124
13 Pyzn 3.36 4128 24 100 98 71.7 115 8258de $710

Etho 1.68 4/28
Desm&phen 0.56 5119
Tfsu 0.0174 5119
Desm&phen 0.56 6/4
Tfsu 0.0174 6/4
Clpy 0.1 05 6/4

14 Cycl 3.36 4127 1 100 100 78.4 117 9174a-d $130
Glyt 0.63 611
Glyt 0.63 6124

15 Cycl 3.36 4127 26 100 98 73.5 119 8789b-e $430

Desm&phen 0.56 5/19
Tfsu 0.0174 5119
Desm&phen 0.56 614
Tfsu 0.01 74 614
Clpy 0.105 6/4

 

16 Cycl 3.36 4127 4 100 100 82.8 119 9868 a-c $105
Glyt 0.63 6117
L500“, 3.9 0.9 2.9 10.3 N/S
CV% 31.7 0.7 2.2 9.4 3.3

 

“Injury was recorded on June 11, 1999.
“Yield represents the weight of sugarbeet root from the ﬁeld in Mg/ha.harvested October 11, 1999.
cWeed control was rated July 20, 1999. Colq — common lambsquarters, Rrpw — redroot pigweed

“Clpy - clopyralid, Cycl — cycloate, Desm&phen — desmedipham and phenmedipham, Etho —
ethofumesate, Glyt - glyfosate, Pyzn — pyrazon, Tfsu - triﬂusulfuron

“Recoverable sugar is the amount of white sugar that can be obtained from the processing of sugarbeet
roots, and is calculated using the yield, percent sucrose in the beet, and approximate purity of the juice.

fAll prices in the tables reﬂect the cost of product, fuel, maintenance, repair, and labor associated with

broadcast application of each herbicide program. Prices only reﬂect operating costs and do not include the
cost of purchasing, owning, or storing equipment

134

Table 27 — Sugarbeet injury“, yield“, and control of common lambsquarters and redroot
pigweedc with pyrazon, ethofumesate, or cycloate followed by postemergence
applications of glufosinate or desmedipham and phenmedipham plus triﬂusulfuron plus
clopyralidd to sugarbeet at the Saginaw Valley Bean and Beet Farm in 1999.

 

 

--- Program--- Rate Applied Injury % Weed Control Yield Recov. Sugar“ Costf
# Herbicide kg/ha Date % Colq Rrpw T/ha kg/T kg/ha We
1 None N/A NIA 0 0 0 49.3 130 6410 e S 0
2 Gluf 0.4 5/27 1 100 100 72 .2 135 9782 a-d 3 170
Gluf 0.4 6/1 7
Gluf 0.4 7/7

3 Gluf 0.4 5/27 0 100 99 73.6 132 9687 a-d 5 115
Gluf 0.4 6/17

4 Desm&phen 0.56 5119 10 99 94 66.5 133 8855 d S 350

Tfsu 0.0174 5119
Desm&phen 0.56 614
Tfsu 0.01 74 6/4
Clpy 0.105 6/4

5 Pyzn 4.48 4/28 1 100 97 69.8 135 9421 a-d 3 345
Gluf 0.4 5/27
Gluf 0.4 6/17

6 Pyzn 2.24 4/28 3 100 100 75.1 136 10174 ab 5 230
Gluf 0.4 5/27
Gluf 0.4 6/17

7 Pyzn 4.48 4128 11 100 99 69.2 133 9234 b-d 5 585

Desm&phen 0.56 5/19
Tfsu 0.0174 5119
Desm&phen 0.56 6/4
Tfsu 0.0174 614
Clpy 0.105 614

8 Etho ' 1.68 4/28 1 100 100 69.9 135 9470 a-d 5 295
Gluf 0.4 6/1
Gluf 0.4 6/24

9 Etho 0.84 4/28 0 100 100 70.7 134 9470 a-d 3 205
Gluf 0.4 6/1
Gluf 0.4 6/24

10 Etho 1.68 4/28 11 100 100 70.7 131 8976 cd 5 535

Desm&phen 0.56 5119
Tfsu 0.0174 5/19
Desm&phen 0.56 6/4
Tfsu 0.0174 614
Clpy 0.105 6/4

11 Pyzn 3.36 4/28 3 100 100 73.7 137 10092 a—c $525
Etho 1.68 4/28
Gluf 0.4 6/1
Gluf 0.4 6/24

135

 

12 Pyzn 1.68 4128 0 100 100 73.2 134 9830 a-d $ 320
Etho 0.84 4128
Gluf 0.4 6/1
Gluf 0.4 6/24
13 Pyzn 3.36 4128 14 100 99 69.9 134 9405 a-d $710
Etho 1.68 4128
Desm&phen 0.56 5119
Tfsu 0.0174 5119
Desm&phen 0.56 614
Tfsu 0.0174 614
Clpy 0.105 6/4
14 Cycl 3.36 4/27 0 100 100 77.8 135 10485a $190
Gluf 0.4 6/1
Gluf 0.4 6/24
15 Cycl 3.36 4127 10 100 99 69.4 133 9236 b-d $430
Desm&phen 0.56 5119
Tfsu 0.0174 5119
Desm&phen 0.56 614
Tfsu 0.0174 614
Clpy 0.105 6/4
16 Cycl 3.36 4127 0 100 97 69.0 132 9087b-d $135
Gluf 0.4 6117
LSDogs 2.9 0.9 2.9 8.4 N/S
CV% 50.7 0.7 2.2 8.3 2.7

 

“Injury was recorded on June 11, 1999.

“Yield represents the weight of sugarbeet root from the ﬁeld in Mg/ha.harvested October 11, 1999.

“Weed control was rated July 20, 1999. Colq —— common lambsquarters, Rrpw - redroot pigweed

“Clpy -— clopyralid, Cycl — cycloate, Desm&phen -— desmedipham and phenmedipham, Etho —
ethofumesate, Gluf — glufosinate, Pyzn — pyrazon, Tfsu - triﬂusulfuron

“Recoverable sugar is the amount of white sugar that can be obtained from the processing of sugarbeet
roots, and is calculated using the yield, percent sucrose in the beet, and approximate purity of the juice.

fAll prices in the tables reﬂect the cost of product, fuel, maintenance, repair, and labor associated with
broadcast application of each herbicide program. Prices only reﬂect operating costs and do not include the

cost of purchasing, owning, or storing equipment.

136

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