Insect Control in Alfalfa

(Duane) Duane Toews joining you with AGam in Kansas. And while at the Kansas Forage and Grassland Council Winter Meeting in Manhattan, a chance to catch up with Jeff Whitworth from K-State Research and Extension, Entomology Department. Jeff, you had the opportunity to talk to growers about insect control in alfalfa and there’s some predominant ones that we seem to have to deal with each and every year. (Jeff) Yes, unfortunately there are. The alfalfa weevil is the one that causes problems every year. It’s one of the two insects in Kansas that I consider to be a serious or severe pest. The other one is the sunflower head moth on sunflowers. But what that means is you have to spray for them every year. So, if you want to, if you do not want to donate part of your crop, you’re going to have to treat for the alfalfa weevil. And that’s the insect of interest for most alfalfa producers in Kansas. The problem with the alfalfa weevil is it’s very active. It comes on very early, anywhere from late February to mid April. And as you know Duane the weather can be very different at that time of year. You can have hot, cold, snow, sleet, all kinds of vagaries in the weather and that causes havoc with trying to control the alfalfa weevil. Plus the alfalfa weevil overwinters in Kansas, but it’s a cool weather insect. So, anytime the temperature’s above 48-50 degrees it’s active. So right now November, December, it’s been laying eggs in the stems so those eggs are developing a little bit. Anytime the temperature is over 48-50 degrees and then they’ll continue to feed, the adults will, they will continue to lay eggs in January, February and March. Those eggs that were laid in November and December will hatch early. Those eggs that were laid in January, February and March won’t hatch until April or May, so you have a two to three month period of time when those eggs are hatching. And those larvae, that’s the damaging stage, are actually feeding on the alfalfa. So, it makes it very difficult to try and time the application of insecticide once you decide you need to treat. With the alfalfa weevil, it’s not so much as if you need to treat, it’s more when are you going to treat. So, that’s what we’ve been looking at is trying to figure out the best way to time applications to help control alfalfa weevils. (Duane) Quick thoughts on the other pest that is typically a problem for us? (Jeff) The other pest that I consider year after year is potato leaf hopper. That’s an insect that I don’t think gets enough credit for as much damage as it does. It can cause damage two different ways. Number one, it sucks the juice out of the plant. Number two, it introduces a toxin into the plant and can cause what we call hopper burn, which is a yellowing of the leaves. If it’s severe enough it go down the stem, can actually kill out a plant. Usually in Kansas in the last few years we haven’t had populations enough to cause death of plants, but in the last two or three years, we are noticing an increase in populations and they don’t overwinter in Kansas. Potato leafhoppers before have not overwintered in Kansas. In the last two years, we’ve found them in late October. And they’re doing damage in late October, which is an anomaly because as you know, most growers cut four times, maybe five times a year and they quit in September, October and let that regrowth occur, so can put some food stalks down into the root system. Well, when you have potato leafhoppers there in October, and November causing the deadening of the plant killing the plants out, that’s not gonna happen. So, we’ve not seen it before I hope it’s just an anomaly, I hope it doesn’t continue to be a problem. But in the last two years, 2014 and 2015, the potato leafhoppers have been here clear up through October. We haven’t looked in November and December and I’m really kind of scared to go out and look, they might still be there. But normally they don’t over winter in Kansas. (Duane) Our thanks to Jeff Whitworth with the Entomology Department at Kansas State University at the Kansas Forage and Grassland Council Annual Meeting and Conference in Manhattan. Jamie back to you.
(Jamie) Thanks for joining us. I’m your host Jamie Bloom and I hope you enjoyed today’s show. See you next week on Farm Factor – we’re here every Tuesday on AGam in Kansas.

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