Master Gardener: Armyworm invasion can be destructive | Home & Garden

It looks like my yard has been invaded with these inch-long caterpillars that are devouring my turf and some of my plants. How do I get rid of them? — T.G.

The insects you are describing are armyworms. We have been getting quite a few questions about armyworms, so let’s talk about what they are and how to get rid of them.

First of all, we call them armyworms, but in reality, they are caterpillars on their way to becoming a moth. These moths will migrate south later this year in search of the warmer climates of the Gulf Coast, Texas or Mexico, only to return to Oklahoma in June next year. Until they leave, they can be quite destructive.

When the armyworm moths return in June, the female moth can lay up to 1,000 eggs in smaller groups of fifty to several hundred. These eggs hatch in July as tiny caterpillars and begin to eat, and they can eat. They can do quite a bit of damage to your lawn or plants, not so much individually, but you can imagine what it would be like if a hundred or so females each laid 1,000 eggs in a concentrated area. A hundred thousand armyworms could do some damage.

The good news is that they don’t have a long feeding season — only about 2-3 weeks. After this feeding frenzy, they go down into the soil to pupate. Two weeks later, the next generation of adult armyworm moths emerge. There can be several generations all the way into October or even November. With this relatively quick life cycle, it’s easy to see how their numbers can build up quickly. Their preferred food is turfgrass, but they will really eat anything. We’ve seen some photos of them even devouring tomatoes this year.