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This is to certify that the

thesis entitled

Common Windgrass (épera gpica-venti L.) Control
in Michigan Winter Wheat

presented by

Andrew James Chomas

has been accepted towards fulfillment
of the requirements for

M.S. degree in Crop and Soil Sciences

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MSU I. An Affirmative ActloNEquol Opportunity Institution
Walla-9.1

 

COMMON WINDGRASS (APERA SPICA-VENT I L.)
CONTROL IN MICHIGAN WINTER WHEAT

By

Andrew J. Chomas

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 Science
1996

ABSTRACT

COMMON WINDGRASS (Apera spica-venti L.) CONTROL
IN MICHIGAN WINTER WHEAT

by

Andrew James Chomas

Field research was conducted in 1992 to 1995 to evaluate the effectiveness of
postplant incorporated trifluralin for the control of common windgrass in Michigan
winter wheat. Trifluralin significantly reduced common windgrass densities in 1992-
1993. Trifluralin applied at 0.56 kg/ha reduced common windgrass density by 85%
and increased wheat yields by 32%. Significant wheat injury and stand reduction
occurred in response to trifluralin incorporation in 1995. Wheat injury increased as
trifluralin rate increased. Effect of incorporation implement on wheat injury was
Fuerst harrow > spike tooth drag > rotary hoe. When shallowly incorporated, no
significant wheat injury was observed at any site from 1992 to 1995 from trifluralin

incorporation at the 0.56 kg/ha rate, when wheat was planted at least 5 cm deep.

ACKNOWLEDGMENTS

The author wishes to thank Dr. James Kells, graduate advisor, for the
opportunity to receive a Master’s Degree in Weed Science at Michigan State University
and for taking the time to help in the accomplishment of this goal. The author would
also like to thank Dr. Stephen Stephenson and Dr. Richard Ward for devoting time to
be on the author’s graduate committee.

The author is deeply appreciative to the “Weed Science Crew” for help on
every aspect of research. In obtaining a degree and work in general, one realizes that
it is not a singular effort. A special thanks to those who listened to my “stories” over
and over again, not to mention the singing. Thanks to the people who went on the

many weekend excursions up North to the festivals and “church” picnics.

iii

TABLE OF CONTENTS

LIST OF TABLES .......................................... vi
CHAPTER 1

REVIEW OF LITERATURE .................................... 1

INTRODUCTION ...................................... 1

COMMON WINDGRASS ................................. 1

Name ..................................... 1

Description ................................. 1

Biology .................................... 2

Habitat .................................... 3

Distribution ................................. 4

Control .................................... 4

WHEAT ............................................ 5

History .................................... 5

Soft White vs. Soft Red Wheat ..................... 6

Spring vs. Winter Wheat ......................... 6

Wheat Production ............................. 6

Tillage ......................................... 7

Pest Management .................................. 8

Insects .................................... 8

Diseases ................................... 8

Weeds .................................... 9

Trifluralin ...................................... 10

History ................................... 10

Chemical Characteristics ........................ 10

Physiological and Biochemical Behavior .............. 10

Mechanism of Action .......................... 11

Behavior in Soil ............................. 11

Microbial degradation ..................... 1 1

Chemical alteration ...................... 1 l

Volatilization .......................... 1 1

Photodecomposition ...................... 12

Weeds Controlled by Trifluralin ................... 12

LITERATURE CITED .................................. 13

iv

CHAPTER 2
COMMON WINDGRASS [Apera Spica-vem‘i L.] CONTROL IN

MICHIGAN WINTER WHEAT ................................. 16
ABSTRACT ......................................... 16
INTRODUCTION ..................................... 18
MATERIAL AND METHODS ............................. 19

General Experimental Procedures ....................... 19
1992-1993 Study ................................. 20
1993-1994 and 1994—1995 Studies ...................... 2O
Production-Scale Research Sites 1994-1995 ................ 21
RESULTS AND DISCUSSION ............................. 21
1992-1993 ...................................... 21
1993-1994 ...................................... 22
1994-1995 ...................................... 22
Production-Scale Research 1994-1995 .................... 23
CONCLUSIONS ...................................... 24
LITERATURE CITED .................................. 25

Table 1.

Table 2.

Table 3.

Table 4.

Table 5.

Table 6.

Table 7.

LIST OF TABLES

Herbicide application information for control of common windgrass.

Production-scale research application information for control

of common windgrass, 1994-1995. .......................

Effect of trifluralin on common windgrass control and wheat

yield, 1992-1993. ..................................

Wheat yield as affected by trifluralin rate and incorporation

method, 1993-1994. .................................

Effect of trifluralin rate and incorporation method on common

windgrass and wheat in Saginaw County, 1994-1995. ...........

Effect of trifluralin rate and incorporation method on common

windgrass and wheat in Huron County, 1994-1995. ............

Effect of trifluralin at 0.56 kg/ha on common windgrass control

and wheat in field-scale research sites, 1994-1995. .............

vi

.27

.30

.33

Chapter 1
REVIEW OF LITERATURE

INTRODUCTION

Common windgrass (Apera spica-venti L.) is an alien weed species that has
become widely distributed in North America. It successfully infests and reproduces in
winter grain culture. Common windgrass has been in Michigan (U.S.A.) nearly one
century, and during the past fifteen years it has caused concern as a crop weed. In
Michigan (U.S.A.), it has increasingly become an economic concern to farmers
growing winter wheat. Common windgrass is not widely distributed in Michigan, with
major infestations primarily in Huron and Sanilac Counties. Infestations have also
been reported in Saginaw County. Currently, no weed control strategy, neither
mechanical nor chemical, is available in Michigan that will provide consistent control

of cormnon windgrass in winter wheat.

COMMON WINDGRASS
Name. Apera spica-venti L. In the United States this species is called common
windgrass. In Canada it is referred to as loose silky bentgrass (15). Common
windgrass, at times, has been included within Agrostis, the bentgrass genus. It is
readily distinguished by using the key outlined in McNeill (15). In Michigan it is often
confused with another plant Agrostis gigantea (Redtop) (9).
Description. Common windgrass may be easily distinguished from the fall cereals that

it infests by its long prominent, membranous ligule and very narrow leaves. It

2
generally overwinters in the two to three leaf stage (1, 16, 30,). According to
Warwick et al. (30), it is an annual ranging from 20 to 100 cm in height. Culms are
tufted or solitary, erect, slender, and smooth. Leaf blades are pointed and flat ranging
from 7 to 25 cm long, 3 to 10 mm wide. The leaves are green, hairless or minutely
hairy, and usually scabrous. The leaf sheaths are smooth or rough near the apex and
are green or purple in color. The ligule ranges from 3 to 12 mm long and is
membranous. Panicles have numerous scattered spikelets which are laterally
compressed, one flowered, often purplish, 2.5 to 3.0 mm long and disarticulating
above the glumes. Panicles are 10 to 25 cm long and 3 to 5 cm wide. Glumes are
unequal in length, membranous, and pointed at the apex. They are also scabrous on
the keel in the upper half. The lower glume is narrowly lanceolate and one nerved.
The upper glume is oblong-lanceolate and three nerved. The lemma is slightly shorter
than the upper glume, lanceolate-oblong, chartaceous, and minutely hairy at the base.
Lemmas are finely five-nerved, having a long subapical straight or flexous awn, that is
5 to 12 mm long. The palea is two nerved and as long as the lemma. The floral axis
(rachilla) extends as a slender filament beyond the floret. Anthers are 1 to 2 mm long.
Grain is tightly enveloped between the hardened lemma and palea (30).
Biology. Common windgrass typically reproduces as a winter annual with only one
generation per year (1, 14, 27, 30). Wallgren et al. (27) concluded that Apera spica-
venti had peak germination in the autumn, with little or no germination during the
following spring after the seeds were "stored" outdoors in the soil.

Common windgrass has one seed per spikelet. Plants have been reported to
produce up to 2000 seeds per plant from the numerous panicles (30). Seed viability
may range from one to seven years, but seldom exceeds two years (34). Seeds exhibit
relatively little dormancy when freshly harvested. It was found that of mature seeds
collected in Britain, about 50% of the seeds could germinate at harvest (14). Wallgren

and Avholm (27) in Sweden found that primary dormancy was broken two to three

3
weeks after shedding when the seeds were stored under dry conditions. Studies
conducted in Czechoslovakia found that seeds collected from various years and
locations showed very different percentages of germination (30).

Seeds of common windgrass germinate mostly at or near the soil surface (0 to 1
cm depths) and only have minimal emergence from depths greater than 1 cm (30).
Aamisepp and Avholm (1) reported that no germination occurred when the seeds were
placed at depths greater than 2 cm. The highest germination was obtained when seeds
were placed at the soil surface.

The seeds also require moist to wet conditions to germinate (14). Wallgren and
Aamisepp (26) found that common windgrass emerged best at a soil moisture of field
capacity. Common windgrass gerrninates at all temperatures between 5 and 30°C (26).

Common windgrass seeds germinates in the fall and over-winter in the two to
three leaf stage (26, 30). Wallgren and Aamisepp (26) report that seedlings emerge
and develop synchronously with winter wheat. However, the period from pollination
to maturity is more compressed in common windgrass and seed is usually shed before
winter wheat is harvested (14). In Michigan, through personal observations, the same
life cycle seems to occur. In Ontario (Canada), most of the seed is shed in summer
from the mature plants before wheat is harvested (35). Wallgren and Avholm (27) note
that the ability of common windgrass to germinate and establish seedlings in the
autumn, with little germination in the spring, is probably one of the reasons for its
importance as a weed in winter cereals.

Habitat. Common windgrass is primarily a winter annual thriving on sandy loam soils
(14). It also grows on coarse textured soils (13). Northam and Callihan (13) in
England noted common windgrass growing on sandy soils and Aamisepp and Avholm

(13) in southern Sweden found high numbers of windgrass on loams and sandy loams.

4

The common windgrass in Michigan, southern Ontario, and its extensive
distribution in Europe suggest that a mesic temperate condition seems favorable for
common windgrass (16).
Distribution. Common windgrass is found in Great Britain but is much more
prevalent in central Europe (14, 27, 30). It is also found in central Asia, northwestern
Africa, Turkey and Caucasus region, and northwestern Iran (16). McNeill (15)
reported Apera spica-venti was first identified in Canada in 1979 at a few farms.
McNeill (15) also stated that Apera spica-venti has been found to be an introduction in
North America and was not common until recently. Common windgrass was first
found on ship ballast and waste lands in the northeastern United States (15).

Some early reports by Beal (3) made reference of Apera spica-venti in areas "near
Lansing," Michigan (9). It was subsequently reported by Gereau and Rabeler (9) that
in July 1980 a specimen submitted for identification from the "thumb" of Michigan
was found to be Apera spica-venti. Gereau and Rabeler (9) also reported that given the
seriousness of the problem in some Canadian sites, the abundance of Apera spica-venti
at the Sanilac County, Michigan, site may give cause for agricultural concern. Further
reports of Apera spica-venti existence in Michigan include Saginaw County (21).
Visual observations in these regions, and personal correspondence with farmers,
confirms that common windgrass has become more common in Michigan during the
19805.

Control. Early chemical control measures for Apera spica-venti involved using
calcium cyanamide (l , 34). Aamisepp and Avholm (1) reported that along with
calcium cyanamid, dichlobenil (2,6-dichlorobenzonitrile) was also used. At the time of
publication neither was still marketed in Sweden (1).

Studies conducted in a field demonstration using trifluralin (2,6-dinitro-N,N-
dipropyl-4-4(trifluoromethyl)benzenamine) at 0.4 kg/ha with fall rye provided 91%

control of common windgrass (35). Trifluralin has a minor use label for preemergence

5
control of Apera spica-venti in fall cereals in Ontario and was registered in 1987 (35).
Currently no chemical control options exist for effective control of common windgrass
in the United States.

Common windgrass can easily be controlled by cultivating the soil in late
autumn after the seed gerrninates (30). The problem arises that common windgrass
usually gerrninates about the same time as winter annual cereal crops. Warwick et al.
(30) also refer to studies that involve various cultural practices such as summer
fallowing, crop rotation, and tillage to eliminate weed populations. The studies
concluded that common windgrass populations may be reduced through these various
practices. However, when intensive cereal cropping over a long period of time was

conducted, an increase in Apera spica-venti population was realized (30).

WHEAT
History. Wheat is an important food crop worldwide. It can be found in our everyday
foods such as cookies, pastas, and bread. A brief history as summarized by Smith (23)
is given.

Rather than attempting to determine an exact origin, botanists, archaeologists,
and geneticists have identified an area of evolution, cultivation, and early movement of
wheat. The earliest evidence places wheat production utilizing diploid and tetra species
around 8000 BC in an area known as the Fertile Crescent now in present day Iran and
Iraq.

Early farming in 8000 BC in the Far East gives indication that early plant
selection was taking place. Gathering the wheat and bringing it to a common thrashing
site may have been the start of identifying non shattering mutations. Other plant
selection criteria, including seed size, hardness, and number of inflorences, may have

led to development of wheat as a potential food crop.

6
Wheat was introduced into New England by the Pilgrims in 1620. Early

government wheat promotions were developed. As the years went on, various wheat
cultivars were introduced. In 1844, 30 cultivars of wheat were grown in one county
alone in New York State. Many cultivars were reported growing in Ohio by 1858.
Many new cultivars were brought in with the immigrants looking for a new beginning
(23).

Soft White vs. Soft Red Wheat. Michigan produced 234,726 ha of wheat in 1994 (7).
Of the wheat planted, 70 to 75% is of the soft white winter class (5). Soft white wheat
is also grown in Ontario, New York, and the Pacific Northwest. The other main class
of wheat grown in Michigan is a soft red winter wheat and is prominent in southern
Michigan (5, 8). Marketing is probably the key factor in choosing which class to
grow. Since most elevators only buy soft white, producers grow primarily soft white
varieties.

Spring vs. Winter Wheat. Most farmers in Michigan plant winter wheat. One reason
is yield potential. Winter wheat generally yields 30% more than spring wheat (4).
Other reasons include weed control and disease management. Hard winter wheat is
predominately grown in the southern Great Plains of the United States (6). Hard red
spring wheat is mostly grown in and around North and South Dakota (6). Distribution
of winter wheat varieties are throughout the northeast United States and the Pacific
Northwest (6).

Wheat Production. Wheat production in North America has doubled since 1950 (6).
However, total hectarage over the past 35 years has remained constant and the
increased production is attributed to changes in yield rather than changes in hectarage
(6). Average wheat yields have doubled between 1949 and 1976, with average wheat
yields in North America rising from 1010 to 2020 kg/ha, respectively (6). Wheat

hectarage in the United States peaked prior to World War II and has not significantly

.7

grown since (6). Donald (6) gives several reasons: government programs, devoting
less productive land to wheat, and economic considerations.

In 1985, Michigan averaged over 4000 kg/ha and was the highest average in the
United States along with being the highest recorded state average for Michigan (4). In
the past years, wheat hectarage in Michigan has trended down since the 1960s (8).
Wheat yield reached a plateau in the 19803 and early 19908 and has been averaging
about 3360 kg/ha (8). Michigan's loss in hectarage, from 445,000 ha in 1960 to
234,726 ha in 1995, was compensated by higher yields to maintain a constant
production level (8). Michigan has the potential to produce wheat. However, varying
hectarage and quality provides for an unstable wheat supply (8). Currently campaigns
to increase productivity of wheat in Michigan have been developed and are being
implemented. Increased attention to weed control is one facet of the program to

revitalize Michigan's wheat producing capability.

Tillage

Tillage management systems for wheat production in the United Sates varies by
region. The factors involved in deciding what tillage practice to include or whether
tillage at all is necessary depend on several factors. Some factors include amount of
residue present, weeds, soil tilth, and previous crop. Erosion control, water and wind,
also play an important role in deciding what tillage to use (12).

Michigan wheat producers plant wheat by a variety of methods. The most
common are minimum tillage, no-tillage, and aerial seeding (28). Generally, Michigan
wheat is planted in rotation with dry beans, soybeans, and sugar beets (29). Planting
wheat after dry beans is advantageous because dry beans are generally harvested during
September; whereas, soybeans are predominantly harvested in October. Planting after
these crops requires different tillage. Sugar beets for instance may have more "ruts"

from the heavy harvesting equipment along with compaction. Tillage allows producers

8

to relieve compaction, remove weeds and provide an adequate seed-bed for the wheat.
Minimum tillage is growing in popularity (29). Minimum tillage practices allows
producers to leave more residue on the soil surface for wind and water erosion (12).

Aerial and broadcast seeding is another planting option. This planting system is
estimated to include 15 to 20% of Michigan's hectarage (28). It is fast and convenient
but caution is advised, due to non-uniform seeding rates and depths (28). It is very
advantageous during periods of extended rainfall when field conditions may become
too wet for field operations.

Tillage equipment varies from producer to producer. Some use disks, field
cultivators, and harrows. The most common may be a one pass system with a field

cultivator. This varies greatly depending on previous crop.

Pest Management

Insects. A host of insect pests inflict damage on wheat (4). The predominant insects
that invade wheat are Hessian fly (Mayetiola destructor (Say)), armyworm (Pseudaletia
unipuncta (Haworth)), cereal leaf beetle (Oulema melanopus (Linnaeus)), English grain
aphid (Sitobion avenae (Fabricius)), bird-cherry aphid (Rhopalosiphum padi
(Linneaus)) corn leaf aphid (Rhopalosiphum maidis (Fitch), and greenbugs (Schizaphis
graminum (Rondani)) (11). Although important, most insect problems can be
controlled below economic impact through cultural and biological means (4). The
Hessian fly is potentially the most serious insect pest of wheat in Michigan (4).
Cultural control is the best control measure for the Hessian fly (4). Planting according
to the "fly-free" date virtually eliminates risks of infestation (11). Tables of the fly
free dates for Michigan and various location have been calculated (11).

Diseases. Good farming practices such as crop rotation, seed treatment, and the use of
resistant varieties are vital in avoiding most disease problems (5). Total yield losses

from disease are estimated to range from 10 to 70% in individual fields (29). On a

9

statewide basis, disease losses are estimated around 25%. Yield losses due to diseases
are difficult to estimate (29). One may have combinations of pests and yield losses
may be attributed to other factors such as fertility, rainfall, and weeds.

Weeds. Information is available on weed distribution, severity, and introduction (6).
However, scientific studies on the impact of specific weeds at various densities on
wheat yields are not abundant (6). Weeds are a problem in winter wheat on numerous
fields in Michigan. However, it may be best to control weeds in other crop rotations,
especially perennial weeds (13). A number of choices may exist for weed control in
other crops such as corn or soybean (13).

If the field contains weeds at planting time, they must be removed with either
tillage or a burndown herbicide (22). Paraquat, 1,1'-dimethyl-4,4'-bipyidinium ion,
and glyphosate, N-(phophonomehtyl)glycine are two common burndown herbicides. If
a herbicide is necessary, the majority is spring applied postemergence in Michigan
winter wheat. Most weed problems affecting winter wheat production in Michigan are
winter annuals, with some annuals occurring in the spring (22). The most critical step
for good weed control in wheat is proper planting procedure (13). Wheat is extremely
competitive with weeds. A healthy, vigorous wheat stand is the single most important
component of a weed control strategy in this crop (13). When weeds are present,
producers may encounter slower harvesting due to weeds in the wheat (4).

Competition between wheat and weeds for light, water, and nutrients may all be
factors in final yield determination (6). The economic analysis of weed control in
wheat has not been studied as a routine part of applied research (6). Determining if
weed control is necessary becomes a judgment rather than a scientific decision. If
weeds are present, at what point do you need to treat? These are all questions that

need to be addressed. On—going research may answer these questions in the future.

10
Trifluralin
History. Ashford et al. (2, 32) reported trifluralin (2,6-dinitro-N,N-dipropyl-4-
4(trifluoromethyl)benzenamine) for the first time as a herbicide in 1960. Eli Lilly and
Company was responsible for both discovery and development of trifluralin (2).
Trifluralin was registered mainly as a preplant incorporated (PPI) treatment for use in
broadleaf crops for control of annual broadleaf and annual grass weeds in the first ten
years following registration (2). Ashford et al. (2) reports that trifluralin's main use
was in cotton (Gossypium hirsutum L.) and soybeans (Glycine max (L.) Merr.) in the
United States; while in Canada, its primary use has been for weed control in rapeseed
(Brassica sp.). In 1976, trifluralin was registered in Canada for green foxtail (Setaria
viridis (L.)) control in wheat by Eli Lilly and Company (2). In the United States,
trifluralin was registered for wheat as a shallow incorporation postplant (PoPI)
treatment for green foxtail (Setaria viridis (L.)) in 1981 (2). The predominant use of
this registration has been on the northern Great Plains devoted to a significant
hectarage of spring wheat (2).
Chemical Characteristics. Trifluralin is a member of the 2,6-dinitroaniline herbicide
family (2). Two other common herbicides in this family are ethafluralin [N-ethyl-n-(2-
methyl-2-propenyl)-2)-2,6-dinitro-4-(trifluoromethyl)benznamine] and pendirnenthalin
[N-(l—ethylpropyl)-3,4-dimethyl-2,6—dinitrobenzenamine] (2). Trifluralin is an orange
crystalline solid with a melting point of 48.5 to 490°C (32).
Physiological and Biochemical Behavior. There is no significant translocation of
trifluralin in crops grown in soil treated with trifluralin (20). Trifluralin affects
physiological growth processes associated with the inhibition of lateral or secondary
root development (17). The roots grown in soil containing trifluralin exhibit a residue
in the region of contact with the herbicide, but its known degradation products are not

translocated into the leaves, seeds, or fruit of a variety of plants (20).

1 1

Mechanism of Action. Trifluralin binds to tubulin, the major microtuble protein. The
herbicide-tubulin complex inhibits polymerization of microtubule at the growing end of
the tubule but has no effect on depolymerization of the tubule on the other end leading
to a loss of microtubule (25). The spindle apparatus becomes absent, preventing the
alignment and separation of chromosomes during mitosis and the cell plate does not
form. Cell wall formation is also a function of the microtubule (31). Trifluralin causes
cortical microtubule loss which may prevent cells from either dividing or elongating.
Vaughn et al. (25) conclude that because cortical microtubule are involved in cell
shape, cells cannot elongate but rather expand in a square shape rather than a
rectangular. The result is swollen or club-shape root tip.
Behavior in Soil. Trifluralin readily adsorbs to soil colloids and thus is not subject to
leaching (10, 32, 33). Trifluralin has a low water solubility, high energy bonding,
and it readily binds to soil colloids during the adsorption process (32).

Trifluralin loss is subject to four processes: microbial attack, chemical
alteration, volatilization, and photodecomposition.
Microbial degradation. Microorganisms contribute to degradation and disappearance
of trifluralin in the soil (19, 31). Microbial degradation occurs more rapidly in flooded
anaerobic than in moist soils (31).
Chemical alteration. Degradation under aerobic soil conditions consists primarily of
N-dealkylation, hydrolytic cleavage of the dipropylamine group to produce the phenolic
derivative, and oxidation of an N-propyl group followed by cyclization to produce the
benzimidazole derivative (31). Under anaerobic conditions, the initial detoxication
reactions are nitro reduction and N-dealkylation. However, non—biological degradation
rates appear to be insignificant (31).
Volatilization. Volatility is an important factor with trifluralin; it was found that high
soil temperature and moisture enhance such losses (19). Spencer and Cliath (24)

reported that when 14 kg/ha was incorporated into 10 cm of soil, the loss rate during

12
the first 24 hours was only 0.0517 kg/ha per day. Surface application rates of 1 to 10
kg/ ha to a wet soil resulted in loss rates up to 4.0 kg/ha per day. Application to dry
soil surface resulted in essentially no volatilization. Volatilization of trifluralin occurs
much more rapidly when applied to the soil surface than when incorporated into the
soil (24). Persistence of trifluralin is increased by incorporation as compared to
surface application and will provide an increase in consistency of herbicidal
performance (18).
Photodecomposition. Photodecomposition is another factor of decomposition of
trifluralin. Most literature reports that trifluralin on the soil surface is subject to photo
decomposition (32) and can be avoided by mechanical incorporation (2).
Weeds Controlled by Trifluralin. Weeds controlled by trifluralin are predominately
grasses and some broadleafs. Some common grasses in Michigan controlled by
trifluralin are barnyard grass (Echinochloa crus-gali), crabgrass (Digitaria sp.), fall
panicum (Panicum dichotomiflorum), and foxtails (Setaria sp.). Broadleafs in
Michigan include common lambsquarter (Chenopodium album) and redroot pigweed
(Amaranthus retroflexus) (22). Zilkey and Capell (35) in Canada reported effective

control of common windgrass with trifluralin.

10.

11.

12.

13.

14.

15.

16.

1 3
LITERATURE CITED

Aamisepp, A. and K. Avholm. 1970. Apera spica-venti in Sweden:
occurrence, biology and control. Proc. 10th Br. Weed Control Conf. pp.
50-55.

Ashford, R, R. B. McKercher, and F. A. Holm. 1990. W
ContmLmflheaLuiNQrthAmgnca. Chp 17 PP- 359 373

Beal, W. J. 1896. W. New York, Henry Holt and
Company. 2:356-357.

Copeland, L. 0., M. L. Vitosh, F. J. Pierce and J. J. Kells. 1989. A
production guide for Michigan wheat. Michigan State Univ. Ext. Bul. E—2188.

15pp.

Copeland, L. O. and R. W. Ward. 1994. Wheat variety and seed selection.
Michigan State Univ. Ext. Bul. E-2517. 4pp.

Donald E- E- 1990. momma.
Chp. 1pp. 1-6.

Fedewa, D. J. and S. J. Pscodna. 1995
1225. Mich. Dept. of Agri. and United States Dept. of Agri.

Ferris, J. N. 1995. Market outlook and the economics of producing and
marketing Michigan wheat. Michigan State Univ. Agr. Ec. Staff Paper 95:11

Gereau, R. E. and R. K. Rabeler. 1984. Eurasian introductions to the
Michigan flora. II. 23:51-56.

Golab, T., W. A. Althaus, and H. L. Wooten. 1979. Fate of [”C] trifluralin
in soil. J. Agri. Food Chem. 27(1):163-179.

Haas, M. and D. Landis. 1994. Insect management in wheat and other small
grains. Michigan State Univ. Ext. Bul. E-2549.

Hickman, J ., J. Jacobsen, and D. Lyon. 1994. WWW
Wheat. NAWG Foundation 415 Second St., NE, Suite 300. Washington, D.
C. 20002-4993 117 pp.

Kells, J. J. 1996. Weed Management in Wheat. Michigan Stat Univ.
Unpublished.

Koch, K. 1968. Environmental factors affecting the germination of some
annual grasses. Proc. 9th Brit. Weed Control Conf.

McNeill, J. 1981. Apera, silky-bent or windgrass, an important weed genus
recently discovered in Ontario, Canada. Can. J. Sci. 61:479-485.

Northam, F. E. and R. H. Callihan. 1992. The windgrasses (Apera Adan,
Poaceae) in North America. Weed Techno]. 6:445-450.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

28.

29.
30.

31.

32.

33.

14

Parka, S. J. and O. F. Soper. 1977. The physiology and mode of action of the
herbicides. Weed Sci. 25:79-87.

Parochetti, J. U. and E. R. Hein. 1973. Volatility and photodecomposition of
trifluralin, benefin and nitralin. Weed Sci. 115: 55- 63.

Parr, J. F. and S. Smith. 1973. Degradation of trifluralin under laboratory
conditions and soil anaerobiosis. Soil Sci. 115: 55 -6.3

Probst, G. W., T. Golab, R. J. Herbier, F. J. Holzer, S. J. Parka, C. van der
Schans, and J. B. Tepe. 1967. Fate of trifluralin in soils and plants. J. Agric.
Food. Chem. 15:592-599.

Rabeler, R. K. and C. A. Crowder. 1985. Eurasian introductions to the
Michigan flora. HI. The Michigan Botanist. 24(2):]25-127.

Renner, K. A. and J. J. Kells. 1996. Weed control guide for field crops.
Michigan State Univ.. Ext. Bul. E—434. pp. 127-135.

Smith, C. W. 1995. '
John Wiley&Sons, Inc. New York, NY, 10158-0012. Chpt. 2. pp. 57-76.

Spencer, W. F. and M. M. Cliath. 1974. Factors affecting vapor loss of
trifluralin from soil. J. Agric. Food Chem. 22:987-991.

Vaugn, K. C. and L. P. Lehnen, Jr. 1991. Mitotic Disrupter Herbicides.
Weed Sci. 39:450-457.

Wallgren, B. E., and A. Aamisepp. 1977. Biology and control of Alopecurus
myosuroides huds. and Apera spica venti L. Proc. EWRS Symp. Methods
Weed Control and Their Integr. pp. 229-241.

Wallgren, B. and K. Avholm. 1978. Dormancy and germination of Apera
spica -vent L. and Alopecurus myosuroides huds. seeds. Swedish J. Agric.
8:1 1-15.

Ward, R. W. and L. O. Copeland. 1994. Seeding practices for wheat in
Michigan. Michigan State Univ. Ext Bul. E-2518.

Ward, R. W. 1992. Wheat, oats, and barley. Michigan State Univ. (SR):53.

Warwick, S. I., L. D. Black, and B. F. Zilkey. 1985. Biology of Canadian
weeds. 72. Apera spica-venti. Can. J. Plant Sci. 65:711-721.

Weed Science Society of America. 1994. Herbicide Handbook. Weed Sci.
Soc. Am., Champaign, IL. p. 298-299.

Weed Science Society of America. 1983. Herbicide Handbook. Weed Sci.
Soc. Am., Champaign, IL. 515 pp..

Wheeler, W. D., G. D. Stratton, R. R. Twilley, L. Ou, D. A. Carlson, and.
M. Davidson. 1979. Trifluralin degradation and binding in soil. J. Agric.
Food Chem. 27:702-706.

34.

35.

15

Zemanek, J. 1980. The control of silky bentgrass and dicotyledonous weeds in
cereal crops. Wheat Documenta, Ciba Geigy, Ltd. Basle, Switzerland. pp.
46-49.

Zilkey, B. F. and B. B. Capell. 1990. Loose silky bentgrass (Apera spica-
venti) control in fall rye (Sceale cereale). Weed Techno]. 42496-499.

Chapter 2
COMMON WINDGRASS [Apera spica-venti L.] CONTROL IN
MICHIGAN WINTER WHEAT
ABSTRACT
Common windgrass is found in Central Europe predominantly, but is also found
in the northeastern and northwestern United States. It is an increasing weed problem in
Michigan winter wheat (T riticum aestivum L.) production. Field research was
conducted in 1992 to 1995 to evaluate the effectiveness of postplant incorporated
trifluralin for control of common windgrass in Michigan winter wheat. Trifluralin
significantly reduced common windgrass densities in the 1992-1993 growing season.
Trifluralin applied at 0.56 kg/ha reduced common windgrass density by 85% and
increased wheat yields by 32%. Studies conducted in 1994-1995 in Huron County
provided 85% or greater control in small plot research and 70% or greater control in
production-scale research. In 1993-1995, studies were conducted to evaluate rotary
hoe, spike tooth drag, and Fuerst harrow as incorporation implements for trifluralin.
In the absence of common windgrass in 1993-1994, wheat density and yield were
unaffected by trifluralin application. in Saginaw County in 1994-1995, incorporation
implement had no effect on initial wheat density. However, in a spring 1995
evaluation, injury was observed. At Huron County significant wheat injury and stand
reduction occurred in response to trifluralin incorporation. Wheat injury increased as
trifluralin rate increased. Effect of incorporation implement on wheat injury was
Fuerst harrow > spike tooth drag > rotary hoe. When shallowly incorporated, no

significant wheat injury was observed at any site 1992 to 1995 from trifluralin

16

17
incorporation at the 0.56 kg/ha rate, when wheat was planted at least 5 cm deep. Data
suggest injury from postplant incorporated trifluralin is related to planting depth, with
increased injury associated with shallower seed placement.
Nomenclature: Trifluralin, 2-6-dinitro-N,N-dipropyl-4-(trifluoromethy1)benzenamine;
common windgrass, Apera spica-venti L.; wheat, T riticum aestivum L. Additional

index words: APESV

18
INTRODUCTION

Common windgrass (Apera spica-venti L.) is an invading weed to North
America from Europe (10, 13, 19). In Europe it is recognized as a major weed
problem in winter cereals (10). McNeil] (10) reported infestations of common
windgrass in the United States around the latter half of the 19th century on ballast and
waste places in the northeastern United States. Early reports from Beal (3) give
reference of common windgrass "near Lansing," in Ingham County, Michigan (6).
Gereau and Rabeler (6) also reported sightings in Kent and Sanilac Counties. Common
windgrass was also found in Saginaw County (16). Gereau and Rabeler (6) stated that
the abundance of Apera spica-venti at the Sanilac County site may give cause for
agricultural concern. Common windgrass is predominantly a problem when a winter
cereal such as winter wheat is grown. Common windgrass may be easily dispersed by
wind and farm machinery (19).

Common windgrass is an annual plant (1, 9, 18, 19). Individual plants have
been found to produce up to 2000 seeds per plant (19). Seed viability ranges from one
to seven years, but often it will not exceed two years (20). Seeds of common
windgrass germinate mostly at or near the soil surface (19). Common windgrass
requires wet conditions for germination (1, 9, 18). Seeds from common windgrass
germinate in the fall and seedlings overwinter in the two to three leaf stage (18, 19).

Control measures have been limited for common windgrass. European growers
have used triazines and urea derivatives for control (20). Michigan currently has no
effective chemical control options in wheat. Mechanical control through tillage is
effective in the fall (19). However, common windgrass gerrninates simultaneously with
winter wheat (9, 18, 19). Chemical control in Canada using trifluralin (2,6-dinitro-
N,N—dipropyl-4-(trifluoromethyl)benzenamine) in fall rye has shown success in
controlling common windgrass (21). Others have tested trifluralin use in wheat (4, 8,

11, 12, 14) investigating the feasibility of using trifluralin for weed control in wheat.

19
Trifluralin as a control measure for common windgrass in winter wheat in Michigan
offers a possible option.
Studies were conducted in Michigan from 1992 to 1995 to 1) evaluate the
effectiveness of trifluralin for common windgrass control, 2) evaluate incorporation
methods for trifluralin in winter wheat, and 3) validate small plot research in

production-scale research sites.

MATERIAL AND METHODS
General Experimental Procedures. Sites were planted with wheat using common
seeding, fertility, and tillage practices consistent with Michigan State University
Extension Bulletin E-2188. Studies were established in tilled fields. Tillage consisted
of disking, field cultivation, or a combination of the two depending on the previous
grown crop. Cultivars grown were all winter 'wheats. Planting dates, depths, and
wheat cultivars are presented for each study in Tables 1 and 2.

A tractor mounted compressed air sprayer was used to apply all herbicide
treatments and was calibrated to deliver 206 L/ha at a pressure of 207 k/Pa using
Teejet1 8003 flat fan nozzles on research sites. On the production-scale research sites,
application equipment varied with cooperator. All treatments were applied postplant
incorporated (PoPI). Incorporation implements were set at a depth of 2.5 cm.
Incorporation was effected immediately after trifluralin application. Detailed
application information for the research studies are presented in Table 1.

Data were subjected to analysis of variance, Fisher's Protected LSD at the 5 %
level for the small plot research and production-scale research. Common windgrass
control and injury were evaluated on a scale with zero representing no visible injury

and 100 representing complete plant death.

 

‘Spraying Systems Co., North Avenue, Wheaton, IL 60188.

20
1992-1993 Study. A field study was established in Huron County, Michigan in 1992.
The soil was a Riverdale-Pipestone complex (Loamy, mixed, mesic Aquic Arenic
Hapludalf). The study was designed as a split-plot with four replications. The main
plot factor was incorporation method. Incorporation methods were none or rotary hoe.
The sub-plot factor was herbicide. Five rates of trifluralin were used: 0, 0.28, 0.56,
0.84, and 1.12 kg/ha. The plot size was 3 m wide and 9 m long. Evaluations of wheat
injury, common windgrass control, and common windgrass densities were taken.
Wheat was harvested and yields determined.
1993-1994 and 1994-1995 Studies. In the 1993-1994 growing season a field study was
conducted in Saginaw County, Michigan. The soil was a Wixom sand (sandy over
loamy, mixed, mesic Alfic Haplaquod) with 2.2% organic matter and a pH of 6.9.
Field studies were conducted in 1994-1995 in Huron and Saginaw Counties. The soil
was a Guelph-londo (fine-loamy, mixed, mesic Glossoboric Hapludalf with 2.2%
organic matter and a pH of 7.6 at the Huron County location. At the Saginaw location
in 1994-1995, the soil was a Wixom sand (sandy over loamy, mixed, mesic Alfic
Haplaquods) with 2.5% organic matter and a pH of 6.6.

All three experiments were designed as split-plots with four replications, except
the Saginaw County location in the 1993-1994 establishment year, which had three
replications. The plot sizes were 4.8 m wide and 9 m long. The main plot factor was
incorporation method. Incorporation methods were none, rotary hoe, spike tooth drag,
and Fuerst harrowz. The subplot factor was herbicide. Five rates of trifluralin were
used: 0, 0.28, 0.56, 0.84, and 1.12 kg/ha.

Evaluations of wheat injury, and common windgrass control were taken.

Wheat was harvested and yields determined

 

2The Fuerst FLEXIBLE TINE Harrow®, Fuerst Brothers, Gibson City, IL,
60936—0427

21
Production-Scale Research Sites 1994-1995. Three on—farm production—scale
research sites were established, each 4 ha in size. Each site represents one of the
incorporation implements and are identified as sites A, B, and C (Table 2).
Incorporation implements evaluated were a rotary hoe, spike tooth drag, and Fuerst
harrow. Fields were divided into strips or tracts of land throughout the 4 ha. The
strips alternated between treated and untreated areas. Incorporation was performed by
the respective incorporation implement to the entire 4 ha immediately following
application.

Wheat density data at all three sites were collected approximately four weeks
after planting in the fall of the establishment year, 1994, and May 5, 1995. Common
windgrass densities were determined May 5, 1995 on all three sites. On May 25, 1995
common windgrass densities were determined on sites B and C. Site A was
discontinued, due to the absence of windgrass and no observed wheat injury. Data was
collected at 10 random locations within each treated and untreated strip. The area of
collection was concentrated in the first 50 m of each strip. Each 4 ha production-scale
research site had at least three treated and untreated areas. Site B was harvested and

yield determined July 19, 1995.

RESULTS AND DISCUSSION
1992-1993. No significant differences between rotary hoe and no rotary hoe were
observed; therefore, data were averaged over incorporation method (Table 3). N 0
visual wheat injury was observed at this site from any treatment. Common windgrass
densities were significantly reduced at all rates of trifluralin when compared to the
untreated plots. Trifluralin applied at 0.56 kg/ha reduced common windgrass densities
by 85% and increased wheat yields by 32%. Significant yield increases were observed

at trifluralin rates of 0.56 kg/ha or higher. Zilkey et al. (21) reported 18 to 100%

22
control of common windgrass using trifluralin postplant incorporated at rates of 0.4 and
0.6 kg/ha in rye.
1993-1994. In the absence of common windgrass, wheat density (data not reported) and
yield were unaffected by trifluralin rate or incorporation method (Table 4).
1994-1995. Data from the Saginaw County site indicated that incorporation method did
not affect initial wheat density (Table 5). However, in a spring 1995 visual wheat
evaluation, injury was observed. Significant wheat injury was observed from the spike
tooth drag and the Fuerst harrow incorporation implements at trifluralin rates of 0.84
kg/ha or higher.

At the Huron County site, significant wheat injury and stand reduction occurred
in response to trifluralin incorporation (Table 6). Injury increased as trifluralin rate
increased. Trifluralin affects root development (15, 11) and as trifluralin rate
increased, root injury increased. Trifluralin caused the wheat injury by contact with
root system of the wheat. Generally, the effect of incorporation implement on wheat
injury was as follows: Fuerst harrow > spike tooth drag > rotary hoe.

A factor that may contribute to increased wheat injury is seed planting depth in
relation to trifluralin placement. The Saginaw County site was planted at 5 cm. The
Huron County site was planted at 3.8 cm. Trifluralin placed at higher concentrations
near the root development zone of the wheat may be the primary cause for the injury.
Although a 2.5 cm incorporation depth was intended, deeper placement may have
occurred. In visual observations, soil disturbance from the incorporation implement
was as follows: Fuerst harrow > spike tooth drag > rotary hoe, which corresponds
with the injury ratings on the wheat. Initial injury may not have occurred at the
Saginaw County site due to a deeper planting depth. Injury occurred after
overwintering on plots with 0.84 kg/ha or higher of trifluralin.

Downward movement of trifluralin in the soil profile is limited by its low water

solubility (5). However, trifluralin does have the potential to move in the soil profile

23
(5, 7). Golab et al. (7) reported that 76 to 95% of the trifluralin remained in the 7.5
cm zone of incorporation and that 91 to 99% of the trifluralin remained in the 0 to 15
cm zone. Trifluralin rate, incorporation depth, seed placement, soil type, and
environmental conditions play an integral role in the risk of wheat injury. Data suggest
that deeper incorporation of trifluralin is related to the increased wheat injury.
Shallower planted wheat may have increased risk of injury, dependant on type of
incorporation implement used and rate of trifluralin.

In Saginaw County, common windgrass densities were not taken. Infestations
of common windgrass became so severe that accurate counts could not be taken.

Yields are not reported due to variability caused by the severe common windgrass
infestation. However, in a visual assessment, trifluralin significantly controlled
common windgrass when compared to the untreated areas (Table 5).

Trifluralin at rates of 0.56 kg/ha or higher provided 75% or greater control of
common windgrass when visually assessed two weeks before harvest in Huron County
(Table 6). Common windgrass densities were reduced by 85% or more by the same
trifluralin rate. No significant yield increases were observed.

Production-Scale Research 1994-1995. Trifluralin applied at 0.56 kg/ha reduced
common windgrass density 70 to 100% when incorporated with a spike tooth drag (Site
B) or Fuerst harrow (Site C)(Table 7). Site A (rotary hoe) was not evaluated due to
insufficient common windgrass populations. Yield was determined at Site B however,
no significant yield increases were observed. Yields were not determined for Sites A
and C.

Significant wheat density reduction was observed at site C (Fuerst harrow)
which was planted at 3.8 cm. Sites A (rotary hoe) and Site B (spike tooth drag) had no
observable injury. These data are consistent with plot research where less injury was

observed when wheat was planted at the 5 cm depth as compared to shallower planting.

24

Trifluralin applied at 0.56 kg/ha reduced common windgrass densities by 85 %
or more at the plot research sites and 70% or more at the production-scale research
sites (Tables 6 and 7), respectively. Zilkey et al. (21) reported, in a field
demonstration experiment with fall rye, trifluralin at 0.4 kg/ha provided 91% control
of common windgrass.

Similar herbicide rates have been established for control of green foxtail
(Setaria viridis L.) in spring wheat using trifluralin postplant incorporated. Ashford et
al. (2) recommends a rate of trifluralin postplant incorporated of 0.56 to 0.84 kg/ha in
Saskatoon, Canada. The actual rate within this range depends on soil type and organic

matter content.

CONCLUSIONS

Trifluralin effectively reduced common windgrass densities. When shallowly
incorporated, no significant wheat injury was observed at any site in 1992 to 1995 from
trifluralin at the 0.56 kg/ha rate, provided the wheat was planted at the 5 cm depth.
Production-scale research provided consistent results when compared to the small plot
research. Planting depth and incorporation method affected wheat injury from
trifluralin. These are critical factors in avoiding wheat injury from trifluralin.

To provide the best results, a protective band of untreated soil must be
maintained between the wheat seed and the surface band of soil treated with trifluralin.
Postplant incorporation of trifluralin requires that the wheat be seeded at least 5.0 cm

deep, after which trifluralin is shallowly incorporated in soil above the seed.

10.

ll.

12.

13.

14.

15.

25
LITERATURE CITED

Aamisepp, A. and K. Avholm. 1970. Apera spica-venti in Sweden:
occurrence, biology and control. Proc. 10th Br. Weed Control Conf. pp.
50—55.

Ashford, R., R. B. McKercher, and F. A. Holm. 1990.
W Chp. 17 Pp- 359-373-

Beal, W. J. 1896. Wig. New York, Henry Holt and
Company. 2:356-357.

Cessna, A. J ., R. Grover, A. E. Smith, and J. H. Hunter. 1988. Uptake and
dissipation of trialliate and trifluralin vapors by wheat under field conditions.
Can. J. Plant Sci. 68:1153-1157.

Duseja D. R., H. V. Akunuri, and E. E. Hohnes. 1980. Trifluralin soil
behavior: persistence, movement and weed control. J. Environ. Sci. Health,
A15(1):65-99.

Gereau, R. E. and R. K. Rabeler. 1984. Eurasian introductions to the
Michigan flora. II. 23:51-56.

Golab, T., W. A. Althaus, and H. L. Wooten. 1979. Fate of [14C] trifluralin
in soil. J. Agric. Food Chem. 27(1):163-179.

Grover, R., A. E. Smith, S. R. Shewchuk, A. J. Cessna, and J. H. Hunter.
1988. Fate of trifluralin and triallate applied as a mixture to a wheat field. J.
Environ. Qua]. 17:543-550.

Koch, K. 1968. Environmental factors affecting the germination of some
annual grasses. Proc. 9th Brit. Weed Control Conf.

McNeil], J. 1981. Apera, silky-bent or windgrass, an important weed genus
recently discovered in Ontario, Canada. Can. J. Sci. 61:479-485.

Miller, S. D. and J. D. Nalewaja. 1983. Fall preplant trifluralin (Treflan)
applications in wheat. N. D. Farm Res. 41(2):31-34.

Morrison, 1. N., K. M. Nawolsky, G. M. Marshall, and A. E. Smith. 1989.
Recovery of spring wheat (triticum aestivum) injured by trifluralin. Weed Sci.
37:784-789.

Northam, F. E. and R. H. Callihan. 1992. The windgrasses (Apera
Adan. ,Poaceae) in North America. Weed Techno]. 6:445—450.

O' Sullivan, P. A. , G. M. Weiss, and D. Friesen. 1985. Tolerance of spring
wheat (T riticum aestivum L.) to trifluralin deep-incorporated in the autumn or
spring. Weed Research. 25:275-280.

Olson, B. M. and R. B. McKercher. 1985. Wheat and triticale root
development as affected by trifluralin. Can J. Plant Sci. 65:723-729.

16.

17.

18.

19.

20.

21.

26

Rabeler, R. K. and C. A. Crowder. 1985. Eurasian introductions to the
Michigan flora. III. The Michigan Botanist. 24(2):]25—127.

Wallgren, B. E. and A. Aamisepp. 1977. Biology and control of Alopecurus
myosuroides buds. and Apera spica venti L. Proc. EWRS Symp. Methods
Weed Control and Their Integr. pp. 229-241.

Wallgren, B. and K. Avholm. 1978. Dormancy and germination of Apera
spica -vent L. and Alopecurus myosuroides huds. seeds. Swedish J. Agric.
8: 1 1-15.

Warwick, S. I., L. D. Black, and B. F. Zilkey. 1985 Biology of Canadian
weeds. 72. Apera spica-venti. Can. J. Plant Sci. 65:711-721.

Zemanek, J. 1980. The control of silky bentgrass and dicotyledonous weeds in
cereal crops. Wheat Documenta, Ciba Geigy, Ltd. Basle, Switzerland. pp.
46-49.

Zilkey, B. F. and B. B. Capell. 1990. Loose silky bentgrass (Apera spica-
venti) control in fall rye (Sceale cereale). Weed Techno]. 42496-499.

27

Table 1. Herbicide application information for control of common windgrass.

 

Application Date
Time of Application
Temperature (C)
Relative Humidity (%)

Soil Temperature
(C at 5 cm)

Date Planted
Planting Depth

Cultivar

 

 

 

1992-93 1993-94 1994-95

Huron Co. Saginaw Co. Huron Co. Saginaw Co.
10/02/92 9/28/93 9/20/94 9/20/94
10:00 am. 4:30 pm. 10:30 am. 4:15 pm.
20 11 29 26

58 80 45 37

13 15 22 18

9/ 30/ 92 9/25/93 9/19/94 9/19/94

5 cm 5 cm 3.8 cm 5 cm
‘Harus’ ‘Chelsea’ ‘Harus’ ‘Chelsea’

28

Table 2. Production-scale research application information for control of common

windgrass, 1994-1995.

 

Approximate Experiment Area
Planting Date

Planting Depth

Incorporation Implement
Trifluralin Rate

Cultivar

 

Site A3 Site Ba Site Ca
4 4 4
10/4/ 94 9/ 1 8/ 94 9/19/94
3.8 cm 5 cm 3.8 cm
Rotary Hoe Spike Tooth Fuerst Harrow
0.56 kg/ha 0.56 kg/ha 0.56 kg/ha
‘Harus’ ‘Chelsea’ ‘Harus’

 

aHuron County, Michigan

 

 

 

 

29
Table 3. Effect of trifluralin on common windgrass control and wheat yield,
1992-1993.l
Common Windgrass Wheat
Trifluralin rate Control Density Yield
kg/ha % pl/m2 100 kg/ha
0 0 238 16
0.28 33 1 19 20
0.56 58 37 23
0.84 65 32 24
1.12 74 27 24
LSDQ05 16 48 5

 

lAveraged over incorporation method (rotary hoe, no rotary hoe).

a.»

 

30

Table 4. Wheat yield as affected by trifluralin rate and incorporation method, 1993-
1994.

 

 

 

 

Trifluralin rate None Rotary hoe Spike tooth Fuerst harrow
kg/ha (100 kg/ha)

0 31 25 29 27

0.28 28 30 34 31

0.56 33 28 34 34

0.84 24 27 33 33

1.12 34 27 34 30

LSD“),a NS

LSDQOSb NS

 

 

alncorporation Method within Rate
bRate within Incorporation Method

31

Table 5. Effect of trifluralin rate and incorporation method on common windgrass and
wheat in Saginaw County, 1994-1995.

 

 

 

Common
Windgrass Wheat
Incorporation Implement Trifluralin rate Control Injury Density
kg/ha % % pl/m of row
None 0 0 0 47
0.28 29 0 39
0.56 43 0 44
0.84 46 3 43
1.12 68 5 41
Rotary Hoe 0 0 1 38
0.28 53 0 39
0.56 38 0 36
0.84 45 0 39
1.12 63 0 37
Spike Tooth Drag 0 0 0 44
0.28 38 1 39
0.56 26 0 37
0.84 26 19 40
1.12 41 24 39
Fuerst Harrow 0 0 0 38
0.28 30 3 41
0.56 58 6 40
0.84 47 18 38
1.12 55 9 40
LSD“),a NS NS NS
LSDWSb 12 9 NS

 

“Incorporation Method within Rate
bRate within Incorporation Method

32

Table 6. Effect of trifluralin rate and incorporation method on common windgrass and
wheat in Huron County, 1994-1995.

 

 

 

Common
Incorporation Trifluralin Windgrass Wheat
Implement rate Control Density Injury Density Yield
kg/ha % p1/m2 % pl/m of row 100 kg/ha
None 0 0 41 0 47 37
0.28 94 4 0 43 40
0.56 95 0 50 36
0.84 91 0 47 38
1.12 95 0 48 33
Rotary Hoe 0 0 62 0 48 34
0.28 74 O 46 36
0.56 88 3 48 38
0.84 98 7 46 38
1.12 90 19 43 35
Spike Tooth Drag 0 0 41 10 44 34
0.28 66 1 1 37 34
0.56 75 19 39 36
0.84 80 24 36 37
1.12 88 20 32 32
Fuerst Harrow 0 0 40 0 43 36
0.28 56 16 13 44 34
0.56 80 21 37 37
0.84 100 0 28 31 38
1.12 88 39 36 36
LSDQOSa NS NS 6 6 NS
LSDMSb 10 15 7 4 NS

 

aIncorporation Method within Rate
bRate within Incorporation Method

33

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