If you’re a soybean grower already entangled in troublesome weed resistance in the state of Arkansas, Mississippi or Tennessee, you might want to grab a seat before reading any further.
Valent U.S.A.’s John Pawlak, product development manager, says that the University of Illinois has confirmed the presence of PPO-resistant pigweed in those three states. In all likelihood, the problem will follow the road map of other resistant weeds and begin spreading north into more production-intense areas of the Midwest.
“Post emergence PPO-resistance has been around for a number of years in waterhemp, as a gene mutation takes place inside the weed that renders post-emerge PPO herbicides ineffective,” explains Pawlak. “Last year that same gene mutation was found in Palmer Amaranth in those three states and it caused quite a bit of a stir on the internet and in the industry this summer.”
Pawlak and Valent are recommending growers dealing with possible post-emerge PPO resistance take a “double down” approach by applying a full label rate of flumioxazin while also adding in a second mode of action like pyroxasulfone (Fierce).
“It’s important to get these postemergence herbicides on before the resistant Palmer can break through the layer of preemergence residual herbicide that was applied earlier in the season,” adds Pawlak.