Glyphosate resistant weeds are on the rise in Midwestern cropping systems and the impact of existing resistant biotypes is expected to increase. Among the most troubling of these are biotypes of common waterhemp. In addition, we face the threat of glyphosate-resistant Palmer amaranth biotypes that have been devastating to cotton production in the South, and have been identified in SW and NW Indiana. Resistant biotypes of this weed are now established in the Midwest and their prevalence and impacts could grow rapidly. It is imperative that we understand the means by which these weeds develop resistance to the most important herbicide used in soybean production, devise effective methods to...