Burndown Weed Control for Corn and Soybeans

Jim Martin and J.D. Green, Extension Weed Scientists, University of Kentucky

The status of weedy vegetation in corn and soybean fields ranges from very clean to very weedy. Burndown treatments applied last fall or during the last few weeks have created a clean seedbed. Burndown treatments that had a soil-residual herbicide look cleaner compared with those that did not have a soil-residual herbicide. This is especially true with marestail. However, do not expect these fields to remain clean for long since the warm temperatures will likely degrade soil-residual herbicides sooner than normal and allow weeds to emerge.

The amount of weedy vegetation in fields that have not yet received a burndown will vary depending on weeds present. With the warmer temperatures cool-season broadleaf weeds such as henbit, purple deadnettle, and common chickweed are maturing earlier than normal and will soon dieback and not likely to be a significant factor unless cooler weather conditions return. However, such weeds as marestail, giant ragweed, ryegrass, and volunteer wheat are growing well and need to be monitored. This may motivate growers to apply burndown treatments earlier than normal in order to manage weeds before they become too large.