Alternatives to Fight Resistant Weeds

(Doug) I’m Doug Shoup. I’m the Southeast Area Agronomist for Kansas State University and a lot of our winter programming this winter has been focused on weed control. And really a lot of our effort has been focused on pigweed control. So, there are several pigweed species in Kansas, but the one that producers are having the most difficult problem with are two particular species. One is common water hemp, it’s found mostly in the eastern third of Kansas. And then the other one which has been more of a recent problem is palmer amaranth. And that is one that’s really exploded in central and western Kansas. And a lot of that is because the herbicide glyphosate and glyphosate has been fantastic and we’ve got a lot of great benefits from glyphosate and there’s still a lot of good benefits from glyphosate. But these two particular pigweed species have developed resistance to glyphosate which has caused some newer challenges for producers. And so some of our emphasis in our weed control meetings this winter has been on focusing on the other cultural practices that we can
do for good weed management. And one of those that we don’t think about a lot of times is the narrower rows. And a lot of times in soybeans is where we have our most difficult problems with pigweed species and so I’ve been stressing to producers that doing simple things like narrowing
our soybean rows from 30 inches down to 15 inches or even less we can get a significant suppression of germination up to about 60 percent germination suppression just by narrowing our soybean rows. Doing some of those little things outside of herbicides can go a long way towards
taking a lot of pressure off of our herbicides to work. But ultimately what the take home message is for producers who are having problems is focus on residual pre emerge herbicides. And still I feel like there’s about three good classes of herbicides that were pre emerged in soybean, that would be a Class Five which is SynCore or Metribuzin or there’s generics of Metribuzin. There’s a Class Fourteen which are what we call the PPO herbicides and those are things that contain sulfentrazone or Valor or Fomesafen, which is in Prefix. And then the other one is the Group Fifteen Class herbicides which are things like Dual, Outlook, Seeduwa and Warrant. And so any sort of combination, two or three of those different classes of herbicides is what I’ve been recommending
producers just as long as we have two mechanisms of action in there, we can get longer active control. We put less selection pressure on the one herbicide that is working for a pre emerge and it’s just a better integrated weed management approach to help produce the amount of herbicide resistance that could develop down the road.

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