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Pre-Harvest Weed Control in Small Grain
These late-season applications are intended to facilitate harvest and reduce clean-out and dockage losses. Performance varies; results are best if weeds are not stressed or approaching maturation. Follow application to harvest intervals. Take special note of risk of drift to adjacent crops-many are highly sensitive to some herbicides and the relatively high rates used on large acreages presents a greater risk.
Small grain pre-harvest herbicides can desiccate weeds and crop and provide perennial weed control. Expectations for
pre-harvest weed control may exceed reality. It is difficult to kill or dry down a 3-foot weed in the same manner as a 3-inch
weed. Lower portions of the weed may not be affected. Plant desiccation requires 7 to 10 days or more if wet and cool after
treatment. All herbicides labeled for pre-harvest application are systemic and slow acting which requires a longer dry down
period as compared to contact type herbicides like bromoxynil or paraquat. The intent of a
pre-harvest treatment should be to
facilitate harvest and reduce harvest loss. Pre-harvest treatments do not decrease yield losses due to weed competition or
prevent weed seed production. Herbicide drift from pre-harvest treatments can cause injury to crops nearby. Consider
sensitive crops (sugarbeet, potato, etc.) and other plants (trees, gardens, etc.) in the general vicinity of the field receiving
treatment. No herbicides are labeled as a harvest aid for use on oats. Paraquat is NOT labeled as a harvest aid in small
grains.
2,4-D as a Harvest Aid
2,4-D at 1.5 to 3 pt/A is labeled as a harvest aid in spring wheat, durum, barley, and rye. Labels vary in crop use. Follow the
label. Apply at the dough stage of spring wheat, barley or rye. Not all 2,4-D formulations are labeled for
pre-harvest
applications. Some 2,4-D labels only allow use on wheat, others allow use on wheat and barley and others allow use on
wheat, barley and rye. Apply only those products that allow intended use. An ester formulation will give better control and
quicker burndown than an amine formulation. If using an ester formulation, use a low volatile formulation to reduce vapor
drift potential. If using an amine, at least 2 pt/A is needed for larger weeds. 2,4-D does not control large pigweed, kochia or
wild buckwheat. Large kochia and other weeds with large stems may not burn down and may stay green.
2,4-D can be tank mixed with glyphosate on spring wheat and durum for additional broadleaf control and grass control.
Follow the glyphosate label. The labels of most formulations of 2,4-D have restrictions of no dairy grazing allowed, a 7-day
waiting period for meat animal grazing, and a 30-day waiting period prior to haying. Do not feed straw to livestock.
Ally + 2,4-D as a Harvest Aid
Ally is labeled as pre-harvest aid in wheat, durum and barley alone or with 2,4-D or on wheat and durum with 2,4-D and/or
dicamba. Ally has a long residue so use only in a continuous wheat or wheat-fallow rotation. Must follow crop rotation
restrictions. Apply Ally at 0.1 oz product/A + 2,4-D at 1.5 to 3 pt/A to wheat, durum, and barley in the dough stage and at
least 10 days prior to harvest. Do not use if crop was treated previously with another SU herbicide. For wheat, Ally + 2,4-D
can be tank-mixed with dicamba for faster dry down and for weed resistance management. Follow the label for crop rotation
restrictions and refer to the 2,4-D and/or dicamba label for grazing restrictions.
Dicamba + 2,4-D as a Harvest Aid
Dicamba is labeled only in North Dakota as a pre-harvest application in wheat and durum applied alone or in a tank-mix
combination with 2,4-D. Apply dicamba at 0.5 pt/A + 2,4-D at 1 to 2 pt/A when wheat is in the hard dough stage and the
green color is gone from the nodes of the stem. Dicamba will provide additional control of wild
buckwheat, kochia, common lambsquarters, pigweeds, sunflower, and Russian thistle. A waiting period of 10 to 14 days is required before harvest. Do not
feed treated straw to livestock. Caution: Drift to broadleaf crops is especially hazardous at this time.
Glyphosate as a Harvest Aid
Glyphosate is labeled as a harvest aid only in spring wheat and durum - not barley or oats. Glyphosate at 0.5 to 2 pt/A of a 3
lb ae/gal concentrate controls annual grass, broadleaf weeds, and quackgrass and suppresses Canada thistle in hard red spring
wheat and durum. DO NOT apply to barley. DO NOT apply to wheat grown for seed as a reduction in germination or vigor
may occur. Glyphosate drift will injure or kill sensitive plants.
Glyphosate should be applied after the hard dough stage (30% or less grain moisture) of the wheat and at least 7 days prior to
harvest by air or ground in 3 to 10 gpa spray volume. See label for adjuvant use. Always add AMS at 8.5 to 17 lb/100 gallons
of water. AMS increases control of annual and perennial weeds and especially control of weeds stressed by dry weather.
AMS also eliminates antagonism from ions and carbonates in hard water. DO NOT use AMS in place of an NIS. Refer to
label for addition of other adjuvants
Glyphosate can be tank mixed with 2,4-D for additional broadleaf control. A ND 2(ee) label interpretation has been granted
allowing use of glyphosate at 0.75 to 2 pt/A + dicamba at 0.25 to 0.5 pt/A for a
pre-harvest application to wheat and durum at
the hard dough stage after green color is gone from stems. Allow a 14 day PHI. The tank-mix can be applied by ground or air.
Landmaster BW as a Harvest Aid
Landmaster BW (glyphosate + 2,4-D isooctyl ester) applied at 3.38 pt/A (54 fl oz/A) to 5.25 pt/A controls annual grass and
broadleaf weeds, quackgrass, and suppresses Canada thistle in hard red spring wheat and durum. DO NOT apply to barley.
DO NOT apply more that 5.25 pt/A as a harvest aid. See paragraph above on glyphosate for application information.
Application should be made after the hard dough stage (30% or less grain moisture) of the wheat and at least 7 days prior to
harvest. DO NOT apply to wheat grown for seed as a reduction in germination or vigor may occur. Be aware of the injury
potential of glyphosate drift on sensitive plants. Do not feed or allow dairy or meat animals to forage on treated plants for 2
weeks after application. Do not feed treated straw.
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