Dr. Curtis Thompson – Weed Control

(Curtis) I am Curtis Thompson, Extension Weed Scientist with Kansas State University. And I was going to visit with you about some of the weed problems that we’re seeing out across the state. We’ve had some significant rainfall across the state and weeds are growing very actively. In some cases we see wheat coming through or weeds coming through the wheat field as we watch growers, it appears that a lot of them are going ahead and harvesting that off. But with the good growing conditions, the weeds are going to take off very quickly. And so it’s going to be really important for growers, once they get that wheat off to begin their weed control efforts to try to manage those weeds before they get too large. And you know just waiting a week’s time as rapid as palmer amaranth grows, it can go from the stubble height to doubling in size if not more. And so it is really important to get after these weeds very quickly. Kochia similarly, with the good moisture growing conditions, it grows very rapidly. Once we see any kind of regrowth and a lot of times in a just a day or two we can see some of this regrowth, it’s sufficient to begin the spraying operation. When we’re spraying wheat stubble we want to be sure that we don’t use just glyphosate alone, because we have a lot of glyphosate pig weeds and glyphosate kochia, so it’s going to be really important to be tank mixing. Well if it’s kochia a product containing dicamba, if it’s pig weed it can be dicamba or 24D with that glyphosate when we’re spraying things down. Or we can use things like atrazine with gramoxone if you’re going to be coming with corn or sorghum next year. So there’s… we have a number of different options. You can also take a look at the weed control guide that can help you choose what you might use on the various crops. The other things that we’ve seen with the good growing conditions is in some of our crops when we didn’t use pre-emergent herbicides for example in grain sorghum, we’re seeing quite a few weeds popping through. Again, the rapid growth of those weeds it’s going to be really important to get post emergent programs going. We’ve had lots of folks out busy cutting wheat, and sometimes spraying post on sorghum gets set aside, but we can’t wait too long. Again things like kochia and palmer amaranth, get out of hand very quickly and so we need to get after those herbicides especially when we haven’t had a pre-emergent herbicide on. We need to get after those weeds in these row crops as well. There was a question about corn, having grown so rapidly folks may have missed their window of opportunity to spray weeds and they’re at this point… really isn’t a whole lot we can do. That corn, again with the good growing conditions, went from 30 inches tall to 48 inches tall so quickly that in some cases we didn’t get herbicides on. We don’t want to go ahead and spray. In a lot of cases we can reduce corn yields, so I wouldn’t recommend it. We just have to deal with the weeds and you know, at the end after physiological maturity, they might consider some kind of a pre-harvest burn down. If you’re a grower and you have a particular question, I would say contact your local county agent and they can either ask us the question or get you in contact with us.
 

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