Hard Red Spring Wheat and Durum Wheat Production Guide
(continued)
A-1050, May 1998
Using good cultural practices is one of many methods of
controlling weeds. Always plant weed free seed, prevent weed seed
proliferation, and clean tillage and harvest equipment between
fields to minimize weed infestations. Selective herbicides, if
used properly, will control weeds satisfactorily without damaging
the crop.
Herbicide effectiveness is influenced by crop
tolerance, weed species, and environment. Herbicides are
generally most effective when climatic conditions promote
vigorous plant growth. Weeds which are growing under
environmental stress generally absorb less herbicide and are more
difficult to control than actively growing plants. However, crops
under stress may be more susceptible to herbicide injury. The
ideal temperature for applying most post emergence herbicides is
between 65 and 85 F. Herbicides are generally less active at low
temperatures than high temperatures (except fenoxaprop and
diclofop). Weeds usually die very slowly or not at all if cool
weather occurs during and after treatment. Herbicides usually
become more active at high temperatures, so crop injury is more
likely to occur if herbicides are sprayed on extremely hot days.
Herbicide Resistance
Herbicide resistance has occurred in three weeds of North
Dakota:
Kochia resistance to sulfonylurea herbicides.
Green foxtail resistance to the dinitroaniline herbicides.
Wild oat resistance to ACCase inhibitor herbicides.
ALS resistant kochia has moved across much of North
Dakota. Extensive use of ALS herbicides has caused resistance to
ALS.
ALS herbicides consist of three different classes: 1)
Sulfonylurea herbicides, 2) Imidazolinones (Assert, Pursuit and
Raptor), and 3) Triazolopyrimidine sulfonanilides (TPS)
(Broadstrike/Python, and FirstRate). Common use and repeated
exposure of any ALS herbicide to kochia will contribute to
resistance if used without following resistant management
strategies. This demonstrates the need to rotate herbicides with
different modes of action when planning a long-term weed control
strategy.
Trifluralin (DNA) resistant green foxtail has occurred
across much of North Dakota where consecutive use of trifluralin
was used in small grain crops, row crops, and fallow. Continuous
small grains, small grain/fallow, or small grain/ sunflower
rotation allows continuous DNA use. Also, the residue resulting
from high rates of trifluralin usually applied in sunflower may
partially control green foxtail in a successive small grain crop.
Continuous use and residue from high rates increases selection
pressure for expression of DNA resistant green foxtail.
ACCase resistant wild oat is found mainly within the
Red River Valley but has occurred in northern North Dakota.
ACCase resistant wild oat is attributed to extensive use of
Hoelon and herbicides containing fenoxaprop (Dakota, Puma, Tiller
and Cheyenne) for wild oat and grass control in small grains and
yearly single and/or multiple applications of Assure II and Poast
in sugarbeet.
Herbicide resistant weeds are most likely to develop by using:
- Single-site-of-action herbicides.
- Long residual herbicides.
- Same mode of action herbicides applied over several
consecutive years or multiple times during a growing
season or with a long residual herbicide.
- Herbicides used as "stand alone" products,
without using other weed control options, such as
cultivation.
For a thorough discussion on weed resistance and management
strategies, refer to the current North Dakota Weed Control Guide,
Circular W-253.
Post Applied Herbicides
Weed control from POST herbicides is influenced by crop
tolerance, weed species, weed size, and climatic conditions.
These factors should be considered in determining the herbicide
selection and rate. A range of rates is given for most of the
herbicides in this circular. The lowest rate of POST herbicides
will be effective under favorable growing conditions when weeds
are small and actively growing. Under adverse conditions of
drought or prolonged cool weather, or for well established weeds,
use the highest suggested labeled rate.
Ideal temperatures for applying most POST herbicides are
between 65 and 85 F. Most weeds are killed slowly below 60 F.
There is danger of some herbicides injuring crops if applied
above 85 F. Avoid applying volatile herbicides such as 2,4-D
ester, MCPA ester and dicamba during hot weather, especially near
susceptible broadleaf crops, shelterbelts, or farmsteads.
Rainfall shortly after POST herbicide application often
reduces weed control because the herbicide is washed off the
leaves before absorption is complete. Herbicides vary in rate of
absorption and in ease of being washed from leaves; therefore,
herbicides vary in response to rainfall. The amount and intensity
of rainfall influence the washing of herbicide from leaves.
Minimum interval between application and rain for maximum
POST weed control.
----------------------------------------------------------
Time Time
Herbicide Interval Herbicide Interval
----------------------------------------------------------
Achieve 1 hr Harmony Extra 4 hr
Ally 4 hr Hoelon 1 hr
Amber 4 hr Landmaster BW 6-12 hr
Assert 3 hr Liberty 4 hr
Avenge 6 hr MCPA amine 4-6 hr
Banvel/SGF/Clarity 6-8 hr MCPA ester 1 hr
Bromoxynil 1 hr Moxy 1 hr
Bronate 1 hr Peak 4 hr
Campaign 6-12 hr Puma 1 hr
Canvas 4 hr Roundup/RT 6-12 hr
Cheyenne 4 hr Roundup Ultra/RT 1-2 hr
Curtail/M 6-8 hr Stampede 80EDF 4 hr
Dakota 1 hr Stinger 6-8 hr
Express 4 hr Tiller 1 hr
Finesse 4 hr Tordon 22K 6-8 hr
Glyphosate 6-12 hr Touchdown 2 hr
Gramoxone Extra 0.5 hr 2,4-D amine 4-6 hr
Guardsman 4 hr 2,4-D ester 1 hr
----------------------------------------------------------
Sprayer Clean Out
Crop injury may occur from a contaminated sprayer. The risk of
damage is greatest when spraying crops highly susceptible to the
previous herbicide and when the previous herbicide is very active
in small amounts. Rinsing with water is not adequate to remove
all herbicides. Some herbicides have remained tightly adsorbed in
sprayers through water rinsing and even through several
tank-loads of other herbicides. Then, when a tank-load of
solution including an oil adjuvant or nitrogen solution was put
in the sprayer, the herbicide was desorbed, moved into the spray
solution, and damaged susceptible crops. Highly active herbicides
that have been difficult to wash from sprayers and have caused
crop injury include Banvel, Pursuit, and sulfonylurea herbicides.
Herbicides that are difficult to remove from sprayers are
thought to be attaching to residues remaining from spray
solutions that deposit in a sprayer. The herbicide must be
desorbed from the residue or the residue removed in a cleaning
process so the herbicide can be removed from the sprayer. Sprayer
clean out procedures are given on many herbicide labels and the
procedure on the label should be followed for specific
herbicides. The following procedure is given as an illustration
of a thorough sprayer cleanup procedure that would be effective
for most herbicides. Common types of cleaning solutions are
chlorine bleach, ammonia, and commercially formulated tank
cleaners. Chlorine lowers the pH of the solution which speeds the
degradation of some herbicides. Ammonia increases the pH of the
solution which increases the solubility of some herbicides.
Commercially formulated tank cleaners generally raise pH and act
as detergents to help remove herbicides. Read the herbicide label
for recommended tank cleaning solutions and procedures.
WARNING: Never mix chlorine
bleach and ammonia, as a dangerous and irritating gas
will be released.
Sprayers should be cleaned as soon as possible after use to
prevent the deposit of dried spray residues. A sprayer should not
remain empty over night without cleaning. Fill the tank with
water to prevent dried spray deposits from forming. A clean
sprayer is essential to prevent damage to susceptible crops from
herbicide contamination. See herbicide labels or the current
North Dakota Weed Control Guide for more information.
Spray and Vapor Drift
Movement of herbicides off target is a problem in North Dakota
as herbicides move from target fields into non-target areas
containing crops or other susceptible plant species. (Refer to
NDSU Extension Circular A-657, Herbicide Spray Drift for
additional information.)
All herbicides can drift as spray droplets, but some
herbicides are sufficiently volatile to cause plant injury from
vapor or fume drift. Herbicide volatility and consequent risk of
damage to susceptible plants increases with increasing
temperature. High volatile esters of 2,4-D or MCPA may produce
damaging vapors at temperatures as low as 40 F while low volatile
esters may produce damaging vapors between 70 and 90 F. Amine
formulations are essentially non-volatile even at high
temperatures. Temperature on the soil surface is often several
degrees warmer than air temperature. Thus, low volatile ester
could be exposed to temperatures high enough to cause damaging
vapor formation, even when the air temperature is below 70 F.
Banvel/SGF/Clarity (dicamba) is also volatile and can drift as
droplets or vapor. Herbicide vapor drifts farther and over a
longer time than spray droplets. A wind blowing away from
susceptible plants during application will prevent damage from
droplet drift, but a later wind shift toward the susceptible
plants could move damaging vapors to the plants. To minimize the
risk of drift injury, 2,4-D ester, Banvel, Banvel SGF, Clarity,
and MCPA ester should not be used near susceptible plants.
Damaging drift to non-target plants is primarily a problem
with herbicides that are toxic in small amounts, such as 2,4-D,
Banvel, Banvel SGF, Clarity, Cyclone CF, Express, Glyphos,
Gramoxone Extra, Harmony Extra, MCPA, Pinnacle, Pursuit,
Roundup/RT, and Tordon. However, all herbicides may drift and
cause significant damage to susceptible nontarget plants, so
caution must be observed with all herbicide applications.
Herbicide-Insecticide Combinations — Some
combinations have been shown to increase crop injury compared to
either pesticide applied alone. Severe crop injury may result
from tank-mixing SU herbicides with organophosphate insecticides.
Most SU labels do not allow addition of Lorsban or malathion. SU
herbicides and insecticides should be tank-mixed only when
experience or research indicated crop safety. Do not tankmix
Stampede 80EDF + MCPAe + oil additive with any organophosphate or
carbamate insecticide as serious crop injury will result. Apply
Malathion 14 days after application.
Herbicide + Fungicide Combinations can provide weed
control and maintain crop protection from some diseases.
Information on pesticide labels usually do give all possible
registered combinations for each crop. The following table gives
information on many possible combinations.
Herbicide/fungicide combinations for small grains.
---------------------------------------------------------------------
Adjuvant
Herbicide Mancozeb with Mancozeb Tilt
---------------------------------------------------------------------
Ally not prohibited yes, if required not prohibited
Amber not prohibited yes, if required not prohibited
Assert not prohibited yes, see label not prohibited
Avenge not prohibited yes, see label not prohibited
Banvel/SGF not prohibited not recommended not prohibited
Bronate see product not needed not prohibited
bulletin 2ee
Buctril see product not needed not prohibited
Cheyenne PROHIBITED PROHIBITED PROHIBITED
Curtail not prohibited yes, if required not prohibited
Dakota see Dakota label PROHIBITED not prohibited
Express not prohibited yes, if required not prohibited
Hrmny Extra not prohibited yes, if required not prohibited
Hoelon see Hoelon label oil additive not prohibited
Spring wheat only
MCPA not prohibited yes, if required not prohibited
Stampede see current label oil additive only PROHIBITED
Tiller see tiller label PROHIBITED yes
2,4-D not prohibited yes, if required not prohibited
---------------------------------------------------------------------
Herbicide Storage Temperatures
Excess herbicide quantities may be exposed to freezing
temperatures in storage. The following information gives the
minimum storage temperature to avoid risk of reduced herbicide
activity.
Do not store below 40 F
Assert, Avenge, Fallow Master, Landmaster BW, Treflan, Tri-4
Do not store below 32 F
Agri-Dex, Far-Go EC, Gramoxone Extra, Puma, Stampede 80EDF,
Stinger,
Do not store below 20 F
Hoelon, Weedar 64
Do not store below 10 F
Cheyenne, Curtail/M, Dakota, Roundup, Tiller.
Do not store below 3 F
Bronate, bromoxynil.
Rotation restrictions for crops grown in North Dakota.
----------------------------------------------------------
HRS/
Herbicide Barley Flax Oat Durum
----------------------------------------------------------
- - - - - - months - - - - -
Accent 8 18 8 8
Accent Gold 8 a 8 8
Achieve 1 4 1 1
Allyb 10 22c 10 1/10
Amber 18d a 18d 0
Assert 0 15 15 0
Aatrex/Atrazine a a a a
Balance (see label)
Banvel/SGF (< 0.25 pt/A)e NCS NCS NCS 3
Banvel/SGF (> 1 qt/A)e 2CS 2CS 2CS 3e
Basis 8 18 8 8
Basis Gold 18 18 18 18
Broadstrike + Dual 4.5 a 4.5 4.5
Broadstrike + Treflan 4 a 18 4
Broadstrike Plus 4 a 4 4
Buckle 0 NCS 16 NCSf
Canvasb 10 22c 10 1/10
Clarity (< 0.25 pt/A)e NCS NCS NCS 3
Curtail/M 1 12 1 1
Exceed (do not use in North Dakota)
Far-Go 0 NCS 18 0
Finesse 16 a 10 0
FirstRate a a a 3
Flexstar 4 2 4 4
Harness NCS NCS NCS 4
Hornet 4 a 4 4
Lexoneg 8g 12 12 8g
Matrix 9 12 9 9
Lightning 9.5 40 18 4
Peak 0 0 0 0
Permit 3 a 3 3
Prowl NCS NCS NCS NCS
Pursuit 18 26 18 4
Python 4 26a 4 4
Raptor 4 18 9 3
Scorpion III 4 a 4 4
Sencorg 8g 12 12 8g
Sonalan NCS NCS NCS NCS
Stinger 0 10.5 0 0
Surpass NCS NCS NCS 4
Tordon (1.5 oz) NCS NCS NCS NCS
Treflan/Trifluralinh NCS 0 18 NCS
----------------------------------------------------------
NCS = Next cropping season after
herbicide application.
2CS = Second cropping season after herbicide application.
Field Bioassay Instructions – Refer to label.
- Do not plant until field bioassay
indicates it is safe. Crop rotation after Aatrex/Atrazine
is rate and soil pH dependant.
- Do not use on soil with pH greater than
7.9.
- Requires 22 months and 22 inches of
precipitation west of Hwy 1 or 34 months and 34 inches of
precipitation east of Hwy 1.
- Barley can be planted 6 months after
application west of highway 83 on soil with pH less than
7.9.
- Any rotational crop may be planted
following an in-crop application of less than 0.25 pt/A
and a normal wheat, barley, or oat harvest. If interval
before harvest is shortened or if herbicide is fall
applied do not rotate to a sensitive crop. For other
conditions, allow 45 days per 1 pt/A of Banvel/Clarity or
2 pt Banvel SGF used excluding days when ground is
frozen.
- Buckle is labeled as a fall treatment in
durum wheat and spring PPI application for durum and HRSW
(some varieties excluded).
- Must add 2 months if soil pH is 7.5 or
above. Wheat and barley can be planted 4 months after
application following lentils or soybeans.
- Oats, sorghum, and annual or perennial
grass crops may be planted at least 12 months after
application in areas that received 20 inches or more of
precipitation during the growing season.
[ CONTINUE ]
[ INDEX ]
A-1050, May 1998
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