Jeff Whitworth

(Jeff) I’m Jeff Whitworth, Extension Specialist in Entomology for Kansas State University. Actually I have primarily the eastern half of the state for field crops and the whole state for structural pests. Right now we’re in a corn field, or near a corn field in Saline County. We’ve been looking at corn insects which are really on the wane right now. There are a lot of corn earworms, which is normal this time of year. The corn earworms are going to finish up feeding in corn and then they’ll be pupating in the soil, and then they’ll be moving out of the soil and the adult moths will be flying over to the soybeans and the sorghum to start over depositing or laying eggs. And those are the crops that we’re going to be scouting and looking at, worrying about over the next probably four to eight weeks. What I’ve seen here in the central part of the state, the moth flight will probably start like I said, in two to three weeks and continue on for another two to three weeks. So any sorghum that’s in the flowering stage will be vulnerable to over position or egg laying by the corn earworm moth. Now in sorghum it’s called the sorghum headworm, same insect. But the sorghum is only vulnerable from flowering to soft dough. The moths will lay the eggs, the larvae will hatch out, and they’ll feed on the grain. They feed right directly on the grain. The nice thing about that is they’re up on the head so that they can be controlled fairly easily with an insecticide application if justified. But the bad part about that is they can do a lot of damage very quickly. The rule of thumb is one larvae causes five percent loss per head. So if, you’ve got one, five percent. Two, ten. You know three, fifteen, etc. So that’s something you need to worry about. But it’s only from flowering to soft dough. Once the sorghum gets into the soft dough stage, the kernels are too hard for the newly hatched larvae to utilize as a food source. And so then they’ll move to soybeans. So, they’ll feed on soybeans. They can feed right on the seed within the pod. They’ll feed on the leaves a little bit. But the defoliation really doesn’t amount to much. It’s what they’re feeding on right inside the pod. Now, I emphasize that because you’ll have bean leaf beetles out in a soybean field. They’ll feed on the pod. The corn earworm, or soybean podworm will feed right on the seed within the pod. So, if you’re scouting your field, or if you’re looking at your pods and your soybeans, if you have holes right where the seeds are, that’s a corn earworm problem. If the pod is eaten on, that’s a bean leaf beetle problem. The difference is the corn earworm or the soybean podworm is only gonna last for two weeks. They’re only gonna be feeding for two weeks. Bean leaf beetles will feed on green pods as they mature, as they continue to come on. So, it makes a big difference on what it is. The corn earworm will have one more generation this year probably, after that. But that’s generally negligible unless you have double crop soybeans or double crop sorghum that’s coming on pretty late. Other than that those are the insects of interest, I would say, for now and the next 30 to 45 days in soybean and sorghum. One other insect question that has come about is the potato leafhopper in alfalfa. And those things because of the weather and the growers have not been able to get in to SWAT their alfalfa in a timely fashion, they’ve caused a lot of what we call hopper burn, the yellowing of the leaves and the yellowing stems, what we call hopper burn. And so I don’t see that being a major problem if you can SWAT your alfalfa. That will remove the eggs, that will remove the potato leafhoppers. You probably won’t have a problem. You probably won’t have to make an insecticide application, but after you SWAT that, after you’ve harvested it, you removed the hay, you need to go back out and check the stubble 14 days later to make sure you’ve got all the potato leafhoppers.

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