Illinois has become the third state behind Arkansas and Tennessee to confirm PPO inhibitor resistance in Palmer amaranth.

 

Southern Illinois University Carbondale, in coordination with testing by the University of Illinois, recently confirmed the protoporphyrinogen oxidase resistance after three populations showed control failure after treatment with active ingredients fomesafen or lectofen.

 

Test results also showed the plants still have one good, un-mutated copy of the gene conferring resistance, suggesting that the sites are still in the early stages of resistance development.

 

Karla Gage, SIU weed scientist and assistant professor, said the discovery of PPO-resistant Palmer amaranth in Illinois is not surprising because of the combination of common use of PPO herbicides, rapid evolution of Palmer amaranth to evolve resistance to multiple herbicide modes of action and the known long-distance dispersal of Palmer seeds with the movement of birds and machinery.

 

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