Controlling weeds growing in wheat stubble fields is a good idea, say Mark Rosenberg and Darrel Deneke, South Dakota State University extension agronomists
Controlling them now will prevent them from producing seed.
It especially critical to prevent seed production from occurring in fields that will be planted to crops with limited options for weed control, such as sunflower, peas, grain sorghum, or annual forages. It is especially difficult to control broadleaf weeds in sunflower or peas, and grassy weeds in sorghum that emerge after the crop emerges.
If the field will be planted to Roundup Ready corn or soybeans, farmers may believe they can just wait and control any weeds that emerge next season with a post-emergence application of glyphosate. However, with the concerns over the rise of glyphosate-resistant weeds, it would be far better to control these weeds and grasses now in wheat stubble. That way, other herbicides with a different mode of action can be tank-mixed with glyphosate to ensure adequate control.
Producers should control weeds in wheat stubble fields by applying the full labeled rate of glyphosate with the proper rate of ammonium sulfate additive. It is also recommended to add 2, 4-D or dicamba to the glyphosate. Tank mixes of glyphosate and either 2, 4-D or dicamba will help control weeds that are difficult to control with glyphosate alone, and will help reduce the chance of glyphosate-tolerant weed populations developing.
Dicamba or 2, 4-D tank mixes with glyphosate may not perform well under dry conditions, particularly on Kochia or Russian thistle. Using paraquat (Gramoxone) with dicamba or 2,4-D ester has been more effective than tank mixes of glyphosate and dicamba or 2, 4-D in these conditions. Remember, paraquat is a restricted-use pesticide and requires an applicators license to purchase and apply. Also, always read and follow the label when using any pesticide.
Further information can be found on postharvest weed control on wheat stubble in the SDSU Extension publication South Dakota Crop Protection Guide – Wheat,