The University of Illinois weed science program has developed some recommendations to manage Palmer amaranth – which can reduce corn and soybean yields to nearly zero if not effectively managed. Weed science researchers at the university say there are three general principles of Palmer amaranth management. One is that prevention is preferable to eradication because it uses tactics to prevent weed seed introduction and weed seed production. Another is that it’s not uncommon for annual herbicide costs to at least double once Palmer amaranth becomes established because there are no soil or foliar-applied herbicides that provide sufficient control of the weed throughout the growing season. The last principle is control of Palmer amaranth shouldn’t be less than 100-percent.
Scientists have made recommendations based on the weed’s germination and emergence characteristics. Those are to be certain to control all emerged Palmer amaranth plants before planting corn or soybean and also apply a full rate of an effective soil residual herbicide no sooner than seven days prior to planting – and no more than three days after planting. Weed scientists Aaron Hager says growers shouldn’t rely solely on glyphosate to control Palmer amaranth. As for recommendations based on Palmer amaranth’s growth rate – scientists recommend scouting fields within 14 to 21 days after crop emergence, apply foliar-applied herbicides before Palmer amaranth plants exceed 4-inches tall, consider adding a soil residual herbicide during the foliar-applied herbicide application, and scout fields 7 to 14 days after the foliar-applied herbicide application to determine its effectiveness. If scouting reveals additional Palmer amaranth emergence – Hager suggests making a second foliar-applied herbicide application before the Palmer amaranth is 4-inches tall.
Source: NAFB News Service