Protect crops against army worms

By Todd Vineyard | Published Wednesday, August 29, 2018

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Wise County agriculture producers should be checking their Coastal bermudagrass pastures for army worm invasions.

August rains have sparked growth and green up of the bermudagrass, making it very attractive for the egg-laying moths and hungry army worm larvae. They can also be a major problem for home lawns.

If you sense that you have a problem, give me a call at the Extension office.

The fall army worm is the most common species at present. The true army worm occurs in the spring.

The fall army worm moth has a wing span of about 1 1/2 inches and is dark grey with white markings on the wings. They lay 50 to several hundred eggs on grass leaves, which hatch in three to five days. Egg masses are covered with grey scales from the female’s body.

Larvae vary in color from pale green to almost black. The life cycle from egg to adult requires about four weeks, depending upon temperature. Fall army worms could be active until frost.

The fall army worm is attacked by several species of parasitic wasps and flies, which keep army worm numbers low.

These benefits are apparently less effective during cool, rainy weather, allowing army worms to increase. Also, army worm moths can fly long distance and quickly increase before natural enemies can catch up. The result is an army worm outbreak.

Three to four army worms per square foot warrant treatment depending upon crop condition. As we plant small grains for early grazing, newly emerged wheat cannot tolerate that many. Young worms are more susceptible to insecticides.

It is estimated that 80 percent of the crop damage occurs in the last three to four days of the army worm’s life. For this reason, damage seems to occur almost overnight.

Sevin 80S, Sevin XLR and Mustang Max are a few insecticides labeled for controlling fall army worms.

If you’d like a list of other approved products give me a call. Some products do have a waiting period from application to harvest so be sure to read and follow the directions on the label.

Todd Vineyard is a Wise County Extension agent.

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