Preharvest Weed Control Options for Small Grain Producers

By Blake Jackson

As small grain harvest approaches, growers may consider preharvest herbicide applications to manage troublesome weeds and improve harvesting efficiency.

According to Penn State Extension Weed Specialist Dwight Lingenfelter, these treatments can also provide an opportunity to suppress perennial weeds before planting double-crop soybeans, cover crops, or late-summer forage.

While fall remains the ideal season for controlling perennial species, preharvest applications can still offer benefits within certain crop rotations.

Producers should keep realistic expectations when using harvest aids. Large, mature weeds are more difficult to control than younger plants, and complete desiccation may take a week or longer, especially under cool or wet conditions.

These products are designed to assist with harvest operations and reduce losses caused by weed interference, rather than increase crop maturity or recover yield already lost to weed competition.

Proper application timing is critical. Applying harvest aids too early may disrupt normal crop development and result in unacceptable herbicide residues.

Growers should carefully follow all label instructions regarding rates, crop stage, preharvest intervals, grazing restrictions, and straw use. Extra caution is also necessary to prevent herbicide drift onto nearby sensitive crops and vegetation.

Several herbicides are labeled for preharvest use in small grains. Certain formulations of 2,4-D ester can be applied to wheat, barley, oats, and rye after the hard-dough stage, provided harvest is at least 14 days away.

Aim can be used as a harvest aid to dry down selected broadleaf weeds and requires the addition of an approved oil-based adjuvant.

Dicamba products, including Clarity, are labeled for preharvest use in wheat and barley when crops have reached the proper maturity stage.

Glyphosate may also be applied to wheat and feed barley after grain moisture declines to approved levels, helping manage difficult weeds before harvest.

Sharpen is another option for wheat, feed barley, and triticale, offering effective weed desiccation when applied according to label requirements.

By selecting the appropriate product and following label directions, growers can improve harvest efficiency while reducing weed pressure for future cropping seasons.

FAQs

• What is the primary purpose of preharvest herbicides?
  To improve harvest efficiency and reduce weed-related harvest losses.
• Can harvest aids speed up crop maturity?
  No, they are not intended to accelerate crop maturation.
• When is the best time to control perennial weeds?
  Late summer and early fall generally provide the most effective control.
• How long before harvest should glyphosate be applied?
  At least seven days before harvest and after the proper grain maturity stage.
• Can large weeds be controlled as easily as small weeds?
  No, smaller weeds are typically much easier to manage effectively.

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