Armyworm invasion?

By Todd Vineyard | Published Wednesday, April 9, 2014

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As I watched the rain and hail last week, it reminded me that we usually see armyworm outbreaks this time of year. I’m optimistic that we’ll continue to receive rainfall, so the risk of insect infestations will increase.

Wise County agriculture producers and homeowners should be checking their small grain fields if hay or grain is still an option and coastal bermudagrass pastures as they begin to green up. Homeowners should also be on the lookout for armyworm invasions in their yards.

Recent rains in the area will encourage growth of bermudagrass and weeds, making it very attractive for the egg-laying moths and hungry armyworm larvae. It is usually this time of year that I start getting reports about armyworm outbreaks.

Producers and homeowners should be checking pastures and landscapes on a regular basis. In addition to feeding on coastal pastures, they can also be a major problem in home lawns, so be on the lookout. If you sense that you have a problem, but aren’t sure, give me a call at the Extension office and I’ll be glad to help.

The fall armyworm is the most common species we hear about, whereas the true armyworm occurs in the spring, which is what we’re facing now. The armyworm moth has a wing span of about 1 1/2 inches and is dark grey with white markings on the wings. Eggs are laid in masses of 50 to several hundred on grass leaves. Egg masses are covered with grey scales from the female’s body. Eggs hatch in about three to five days, and larvae vary in color from pale green to almost black. The life cycle from egg to adult requires about four weeks, depending upon the temperature.

The armyworm is attacked by several species of parasitic wasps and flies, which help keep armyworm numbers low. These beneficial insects are apparently less effective during cool, rainy weather, allowing armyworms to increase. Also, armyworm moths can fly long distance and quickly increase before natural enemies can “catch up.” The result is an armyworm outbreak.

Generally, three to four armyworms per square foot warrant treatment, depending on crop condition. Young worms are more susceptible to insecticides. It’s estimated that 80 percent of the crop damage occurs in the last three to four days of the armyworm’s life. For this reason, damage seems to occur almost overnight. Sevin 80S, Sevin XLR, Lorsban and Mustang Max are just a few insecticides labeled for controlling armyworms. Some products do have a waiting period from application to harvest so be sure to read and follow the directions on the label.

For additional information about armyworms and a full list of insecticides available for control in pastures and landscapes, visit the Wise County Texas AgriLife Extension Service Facebook page at

We will also have it on our Twitter and blog page.

Homeowners might also be interested in “Armyworms in Turfgrass.” Read it at

Todd Vineyard is a Wise County Extension agent.

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