Glyphosate Resistant Weeds Got Questions? We’ve Got Answers 1.Are glyphosate resistant weeds real? YES

Confirmed Glyphosate Resistant Weeds in the U.S. Horseweed (Marestail) Common Ragweed Giant Ragweed Palmer Amaranth Common Waterhemp Hairy Fleabane Italian Ryegrass Rigid Ryegrass Johnsongrass Annual bluegrass Goosegrass

Glyphosate Resistant Weeds Got Questions? We’ve Got Answers 1.Are glyphosate resistant weeds real? Yes – here’s giant ragweed “3 qt/a glyphosate” ResistantNormal No spray

2. What causes glyphosate resistance? - A natural mutation or variation in a weed population. - Repeated use of glyphosate that selects resistant types, which increase in number. Glyphosate Resistant Weeds Got Questions? We’ve Got Answers

3. What should be done? Maintain herbicide diversity –Rotate glyphosate with non-glyphosate herbicides. –Use preemergence herbicides before glyphosate or tank mix other herbicides with glyphosate. (Roundup Ready crops don’t have to be sprayed with glyphosate) Glyphosate Resistant Weeds Got Questions? We’ve Got Answers

4. Won’t tank mixing other herbicides with glyphosate fix the problem if glyphosate resistance develops? Perhaps yes, perhaps no. Waterhemp glyphosate resistant + ALS resistant (Raptor, Pursuit, etc.) + PPO resistant (Cobra, Flexstar, etc.) Glyphosate Resistant Weeds Got Questions? We’ve Got Answers K. Bradley, Univ. of MO

5. Won’t new herbicides or technologies be developed to solve the resistance problems? No “new” herbicides are being developed. - Only 1 new mode of action developed in the last 20 years for corn and soybeans – the Callisto family New seed traits may not provide a solution for all resistant weed problems. Glyphosate “Technologies” are valuable – let’s work to protect them. Glyphosate Resistant Weeds Got Questions? We’ve Got Answers