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Effectiveness of Difenzoquat (Avenge) in Wild Oat Control in Small Grains, Lecture notes of Agronomy

The use of difenzoquat (avenge) as a postemergence herbicide for wild oat control in barley, winter wheat, and durum wheat. The study compares the effectiveness of difenzoquat to barban (carbyne) and triallate (far-go) and evaluates the impact of different wheat varieties and herbicide combinations on wild oat control and crop yield.

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DIFENZOQUAT (AVENGE)
A NEW HERBICIDE
FOR WILD OAT CONTROL
S.D.
Miller,
John
D.
Nalewaja
and
C.E.G.
Mulder
ABSTRACT
Wild
oat
causes
yield
losses
and
additional
production
costs
estimated
at
over
S150
million
per
year
in
North
Dakota.
Difenzoquat
(Avenge)
is
a
new
postemergence
herbicide
for
wild
oat
control
in
barley,
winter
wheat.
durum
wheat,
and
several
spring
wheat
varieties.
Certain
wheat
varieties
have
been
nearly
as
susceptible
to
difenzoquat
as
wild
oat,
so
use
only
for
wheat
varieties
listed
on
the
label.
Introduction
Wild
oat
(Avena
fatua
L.)
continues
to
be
the
most
troublesome
annual
weed
in
small
grains
in
North
Dakota.
A
survey
conducted
in
1973
(5)
indicated
57
percent
of
the
small
grain
acreage
in
the
state
was
moderately
to
heavily
infested
with
wild
oat.
Wild
oat
can be controlled effectively in small grains
by preemergence applications'
of
triallate (Far-go) or
postemergence applications
of
barban
(Carbyne);
however, farmer acceptance
of
these herbicides has
not
been extensive. Triallate requires applications before
the wild
oat
is
visible
and
barb
an
is
only effective
on
wild
oat
in the
1-
to 2-leaf stage (4).
Further,
applica-
tion
of
barban
is
not always possible during the
limited period
of
wild
oat
susceptibility because
of
adverse weather.
Difenzoquat (Avenge) has shown promise as a
selective postemergence herbicide for wild
oat
control
at
the
3-
to
5-leaf stage (3,7). Difenzoquat would thus
allow control
of
larger wild
oat
than
barban
and
would allow control over a longer time. Experiments
were conducted
at
several locations
throughout
the
state
to
evaluate difenzoquat for wild
oat
control in
barley
and
wheat.
Materials
and
Methods
Wild oat control
in
barley and wheat. Six experi-
Dr.
Miller is
assistant
professor.
Dr.
Nalewaja is professor.
and
Dr.
Mulder is research associate,
Department
of
Agronomy. Cooperative
investigation
by
the
ND
Agric.
Exp.
Stn
..
and The Agric. Res.
Ser
..
u.s.
Dept.
of
Agric.
ments were conducted
at
experiment stations through-
out
North
Dakota
in
1975
and
1976
on
land
moderately
to
heavily infested with wild
oat
(40
to
90
plants per square yard). Beacon barley was seeded
May
10
and
31
at
Minot
and
Langdon
in 1975, April
13
and
May
11
at
Fargo
and
Minot in 1976,
and
Hector barley May 20
and
27
at
Williston in
1975
and
1976; respectively.
Olaf
wheat was seeded May
16
and
31
at
Williston
and
Langdon
in 1975, April
13
and
27
at
Fargo
and
Williston in 1976,
and
Ellar wheat May
10
and
April
13
at
Minot
in
1975
and
1976;
respectively.
Barban
was applied with a bicycle wheel plot
sprayer
at
the 1.5-
to
2-leaf stage
of
wild oats
and
difenzoquat
at
the 3.5-
and
5-leaf stage.
The
crops
generally
had
0.5
to
1
more
leaves
than
the wild
oat
when treatments were applied. Treatments were
applied in 8.5 gallons per acre (gpa) water
at
a pres-
sure
of
40
pounds
per
square
inch (psi) except
barban
which was applied in 4.7
gpa
water at 45 psi in 1976.
Visual ratings for wild
oat
control
and
crop injury
were
made
after the
crop
and
wild
oat
had
headed.
DiJenzoquat
in
combination with several herbicides
for
broadleaf weed control. Beacon barley was seeded
at
Fargo
in a silty clay soil April
13
in 1976. Herbicide
treatments were applied to wild
oat
in the 4.5-
to
5-leaf
and
barley in
the
6-leaf stage. Difenzoquat-broadleaf
herbicide combinations were applied as a tank-mix in
8.5 gpa water
at
40
psi. Visual weed control ratings
were
made
after
the wild
oat
and
barley
had
headed.
Wheat variety response.
Hard
red spring
and
durum
wheat variety susceptibility
to
difenzoquat was
evaluated at
Fargo
in silty clay soil from 1974 to 1976.
Seeding dates ranged from April
15
to
June
1
depending
upon
the year. Treatments were applied in
19
pf3

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DIFENZOQUAT (AVENGE)

A NEW HERBICIDE

FOR WILD OAT CONTROL

S.D. Miller, John D. Nalewaja and C.E.G. Mulder

ABSTRACT

Wild oat causes yield losses and additional production costs estimated at over S150 million per year in North Dakota. Difenzoquat (Avenge) is a new postemergence herbicide for wild oat control in barley, winter wheat. durum wheat, and several spring wheat varieties. Certain wheat varieties have been nearly as susceptible to difenzoquat as wild oat, so use only for wheat varieties listed on the label.

Introduction

Wild oat (Avena fatua L.) continues to be the most troublesome annual weed in small grains in North Dakota. A survey conducted in 1973 (5) indicated 57 percent of the small grain acreage in the state was moderately to heavily infested with wild oat.

Wild oat can be controlled effectively in small grains by preemergence applications' of triallate (Far-go) or postemergence applications of barban (Carbyne); however, farmer acceptance of these herbicides has not been extensive. Triallate requires applications before the wild oat is visible and barb an is only effective on wild oat in the 1- to 2-leaf stage (4). Further, applica tion of barban is not always possible during the limited period of wild oat susceptibility because of adverse weather. Difenzoquat (Avenge) has shown promise as a selective postemergence herbicide for wild oat control at the 3- to 5-leaf stage (3,7). Difenzoquat would thus allow control of larger wild oat than barban and would allow control over a longer time. Experiments were conducted at several locations throughout the state to evaluate difenzoquat for wild oat control in barley and wheat.

Materials and Methods

Wild oat control in barley and wheat. Six experi-

Dr. Miller is assistant professor. Dr. Nalewaja is professor. and Dr. Mulder is research associate, Department of Agronomy. Cooperative investigation by the ND Agric.

Exp. Stn .. and The Agric. Res. Ser.. u.s. Dept. of Agric.

ments were conducted at experiment stations through out North Dakota in 1975 and 1976 on land moderately to heavily infested with wild oat (40 to 90 plants per square yard). Beacon barley was seeded May 10 and 31 at Minot and Langdon in 1975, April 13 and May 11 at Fargo and Minot in 1976, and Hector barley May 20 and 27 at Williston in 1975 and 1976; respectively. Olaf wheat was seeded May 16 and 31 at Williston and Langdon in 1975, April 13 and 27 at Fargo and Williston in 1976, and Ellar wheat May 10 and April 13 at Minot in 1975 and 1976; respectively.

Barban was applied with a bicycle wheel plot sprayer at the 1.5- to 2-leaf stage of wild oats and difenzoquat at the 3.5- and 5-leaf stage. The crops generally had 0.5 to 1 more leaves than the wild oat when treatments were applied. Treatments were applied in 8.5 gallons per acre (gpa) water at a pres sure of 40 pounds per square inch (psi) except barban which was applied in 4.7 gpa water at 45 psi in 1976. Visual ratings for wild oat control and crop injury were made after the crop and wild oat had headed. DiJenzoquat in combination with several herbicides for broadleaf weed control. Beacon barley was seeded at Fargo in a silty clay soil April 13 in 1976. Herbicide treatments were applied to wild oat in the 4.5- to 5-leaf and barley in the 6-leaf stage. Difenzoquat-broadleaf herbicide combinations were applied as a tank-mix in 8.5 gpa water at 40 psi. Visual weed control ratings were made after the wild oat and barley had headed.

Wheat variety response. Hard red spring and durum wheat variety susceptibility to difenzoquat was evaluated at Fargo in silty clay soil from 1974 to 1976. Seeding dates ranged from April 15 to June 1 depending upon the year. Treatments were applied in

8.5 gpa water at 40 psi when the plants were in the 4 to 5-leaf stage. Visual ratings were made three to five weeks after treatment.

Results

'Wild oat control in barley and wheat. Wild oat control was 17 and 19 percent better with difenzoquat at 12 and 16 oziA than with barban in barley ~Table 1). Difenzoquat at 12 and 16 oz/A gave similar wild oat control of 86 and 88 percent, respectively. Further, barley was very tolerant of the rates of difenzoquat and barban applied. Barley yields were increased 5. and 4.9 buiA by 12 and 16 oz/A of Difenzoquat or 5. bul A by barban when compared to the untreated control plots. The better wild oat control with difenzoquat compared to barban was not reflected in a higher yield because of the earlier removal of wild oat with barban.

Wild oat control was 14 and 18 percent better at the 3.5·1eaf stage or 27 and 31 percent better at the 5-leaf stage with difenzoquat at 12 and 16 oz/A than with barban in wheat ~Table 2). Wild oat control was similar with both difenzoquat rates regardless of stage at ap plication. However, difenzoquat application at the 5 leaf stage of wild oat was 13 percent more effective than at the 3.5-leaf stage. Difenzoquat at 16 oz/A ap plied at both stages of growth caused wheat injury rated visually at 6 to 10 percent. However, recovery from injury was good as no symptoms other than a two to three day delay in maturity were observed. Wheat yields were increased 5.0 and 5.9 bul A at the 3.5-leaf stage or 4.8 and 4.6 bu/A at the 5-leaf stage by difenzoquat at 12 and 16 oz/A or 5.5 buiA by barban when compared to the untreated control plots. Again, the better wild oat control with difenzoquat at both stages compared to barban was not reflected in a higher yield.

Difenzoquat gave 11 percent better wild oat control at the 3.5-leaf stage of wild oat in barley than wheat when averaged over 12 and 16 oz/A ~Table 1,2). The better wild oat control in barley was probably because barley competes with wild oat better than wheat. Crop competitiveness has been reported to influence wild oat control with difenzoquat ~3). Difenzoquat was not applied at the 5-leaf stage in barley; however, wild oat control probably would have been increased similarly to the increase observed in wheat.

Difenzoquat in combination with several herbicides for broadleaf l1'eed control. The addition of 2, 4-D DMA ~dimethylamine) or LVE (low volatile ester), MCPA DMA, or bromoxynil plus MCPA ester had no effect on wild oat control with difenzoquat (Table 3). Wild oat control with the various treatments ranged from 90 to 92 percent. O'Sullivan et al. ~6) have re ported that ester formulations of 2,4-D tended to en hance the effectiveness of difenzoquat on wild oat in Canada. However, this study indicated no enhance ment or loss of wild oat control from the addition of either 2,4-D ester or amine to difenzoquat. Difenzo

quat did not reduce common lambs quarters control with any of the broadleaf herbicides. Barley yields were increased 4.4 to 4.8 bul A by difenzoquat in com bination with the broadleaf herbicides when compared to the untreated control plot.

Wheat variety response. Hard red spring wheat varieties were generally more susceptible to injury with difenzoquat than durum wheat varieties ~Table 4). Durum varieties were all similarly injured at about 19 percent with 16 oz/A difenzoquat; whereas, spring wheat variety injury ranged from 23 to 62 percent. Spring wheat varieties Waldron and Tioga were the most susceptible to difenzoquat. Susceptibility of Era and Kitt to difenzoquat was similar to the durums. Further, Era and Kitt tended to be slightly more resistant to difenzoquat than Olaf or Ellar at 16 oz/A and the difference was more pronounced at higher difenzoquat rates (data not shown).

Discussion Difenzoquat provided excellent postemergence wild oat control in barley; however, selectivity in wheat was influenced by cultivar. The use of difenzoquat in a wild oat control program should be limited to barley and tolerant wheat varieties. Waldron and Tioga were the most susceptible wheat varieties to difenzoquat and on occasion were as susceptible as wild oat. Spray ing Waldron and Tioga with difenzoquat is not recom mended. Difenzoquat has given more consistent wild oat control when applied at the 5- and 3-leaf stage of wild oat. However, with heavy wild oat infestations, applications should be at the earliest stage of growth to minimize competitive losses. Further, the highest labeled difenzoquat rate should be used when early applications are made to dense stands of wild oat to maximize control. Time of application could be delayed and the lowest labeled difenzoquat rate used with light wild oat infestations without greatly reducing yield.

Even though difenzoquat did not increase crop yields above those obtained with barban, wild oat seed production should have been reduced more than with barb an because of the better wild oat control. The influence of a treatment on wild oat seed production is important when considering future infestations. Difenzoquat was compatible with MCPA, 2.4-D or bromoxynil plus MCPA which allows the control of both broadleaf weeds and wild oat with one applica tion.

Greenhouse and growth chamber experiments conducted at North Dakota State University have indicated that climatic and soil factors which promote plant growth have generally enhanced wild oat control with difenzoquat. Field observations have confirmed that adequate soil moisture and fertility enhance wild oat control in wheat and barley. These conditions not only enhance difenzoquat activity, but also promote greater crop competition with wild oat.