Managing Resistant Weeds

(Curtis) Curtis Thompson, I am Extension Weed Specialist for Kansas State University. And we were here today talking to corn growers about weed management and what we really need to do to manage the resistant weed populations that we’re dealing with here in Kansas. This is especially true for weeds like Mare’s Tail, for weeds like the Pigweed species both Palmer Amaranth and Water Hemp. And of course, the Mare’s Tail we did focus on Fall application, very tiny or newly emerged Mare’s Tail are easy to control with a lot of different products. We do have a number of products available for us that can go on in Fall or early Spring, ahead of corn that effectively manage Mare’s Tail. Of course, the real challenge for all of us are the strategies that we need to use to manage Pigweed, again both Palmer Amaranth and Water Hemp and with the planting dates of corn often falling in April, it simply means that we need to have a pre-emergence product in place. And I emphasize the fact that you must use a pre if you want to be consistent in terms of being able to manage the Pigweed populations. And we walk through the different classes of herbicides that have good activity on the Pigweeds. That still includes things like the Chloroacetamide type of products. Of course, Atrazine in the mix with those. We have some PPO herbicides like the Sharpen, the Verdict, Valor, Fierce and of course, there’s various different types of use requirements for those particular products. We also have a whole group of HPPD inhibitors again that have excellent activity. We talked about using herbicides with multiple modes of action, things like Lexar, Lumax, Acuron, the SureStart Two, the TripleFLEX, the Trisidual. So, there’s a number of different herbicides that we touched on. And the other focus, once we have that pre in place, is when we need to use a post, that the post applications are done in a very timely manner. And we emphasize the fact that six, eight, twelve inch Pigweed is not timely post emergence application. But in fact, if we’re looking at one and two inch Palmer Amaranth I think…and Water Hemp, we have a much better opportunity to try to control those if they’re glyphosate resistant with some of the other products. We also then walk through the various resistances that we have found in the Pigweeds, the ALS resistant, the Triazine resistance, of course glyphosate resistance, PPO resistance and HPPD resistance. And so all of these resistances are creating some significant challenges for us. We did kind of wrap up our presentation saying that I do think if things are, if strategies are implemented in the timely fashion, if we spray our post emergence treatment on small weeds, we can manage these Pigweed populations and our glyphosate resistant weeds. We kind of ended with the fact that it’s not going to be cheap in total cost of some of these programs is going to be very high, but we also need to manage these Pigweed populations very seriously for the next two to three, four, five years to try to reduce that Pigweed population out there that’s currently infesting our acres and causing such serious problems.

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