Is 80% of Iowa waterhemp really resistant to Group 14 herbicides?
The University of Illinois Plant Clinic recently published results of their 2016 herbicide resistance screening program. For a $50 fee the Clinic analyzes waterhemp for resistance to both Group 9 (glyphosate) and Group 14 (PPO inhibitor) herbicides. Unfortunately, samples from Iowa displayed a high frequency of resistance to both herbicides (Table 1).