Kurt Vollmer, Extension Weed Management Specialist
University of Maryland
As the 2020 planting season begins, marestail is bolting and common ragweed has started to emerge (Fig. 1). Populations of marestail in the region are resistant to glyphosate and ALS-herbicides (Group 2, i.e. Classic), and populations of common ragweed are resistant to glyphosate, the ALS-herbicides, and PPO-herbicides (Group 14, i.e. Reflex). Herbicides such as 2,4-D, dicamba, and Gramoxone will provide control of emerged weeds, but they are most effective when applied to weeds less than 4 inches tall. Now is the time to spray these weeds. If you have already burned down your field, scout before planting to make sure these species have not escaped or emerged since your burndown application. If they have, consider adding Gramoxone to your at planting application. Dicamba can be used prior to planting Xtend soybeans or 2,4-D can be used with Enlist crops. Always consult the label for application instructions and approved tank-mixes.
