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Is 80% of Iowa waterhemp really resistant to Group 14 herbicides?

February 12, 2017 9:47 AM
Blog Post

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).

On a weed and a prayer

May 27, 2016 6:27 AM
Blog Post

Researchers at the University of Illinois recently published a paper identifying the PPO resistance mechanism in Palmer amaranth.  It turns out that both Palmer and waterhemp have an unusual type of mutation providing resistance to the group 14 herbicides (PPO inhibitors).  Rather than a substitution in the nucleotide sequence coding for the PPO enzyme, the two pigweeds have a deletion of three nucleotides.  The mutation results in an altered form of PPO, therefore providing resistance to the group 14 herbicides.