Herbicide Resistant Weeds in the Region

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Poor weed control can be attributed to many factors, but herbicide resistance is a major consideration. Once a resistant weed population develops in a field, that herbicide is no longer effective; in fact, most other herbicides within that group are also ineffective. We have confirmed resistance in the following summer annual weed species in Delaware:

Weeds are constantly evolving resistance to herbicides and seeds from resistant populations are readily moved by machinery and wildlife. Knowing what other resistant biotypes are in the region can be helpful for early detection and managing new infestations. I talked to weed scientists from some of the other states in the region (MD, VA, and NC) and here are other confirmed instances of herbicide resistance.