Published on 09/17/98

Fall Armyworms Marching Through North Georgia

North Georgia lawns are under attack. Fall armyworms are chewing their way through turf, leaving destruction in their wake. And University of Georgia scientists say they've only just begun to bite.

"This year is the worst for caterpillars of all kinds that I've seen in 20 years," said Will Hudson, an Extension Service entomologist with the UGA College of Agricultural and Environmental Sciences.

"If you haven't yet seen fall armyworms on your turf this fall, it's very likely you will, and soon," said UGA horticulturist Walter Reeves.

Fall armyworms are the caterpillar stage of a nondescript, small gray moth which overwinters in Florida and the tropics. Each year, storms bring the adult moths north. The females lay masses of up to 700 eggs on just about everything.

In a recent test, Hudson put 15 small flags on a turf plot. Just 24 hours later, each flag had at least one egg mass. Some had more than a dozen.

"The eggs are cream-colored at first, but turn darker as the tiny caterpillars get ready to hatch," Hudson said. "They're covered with gray fuzz from the female's body."

The first sign that enemy armyworms are near might be birds clustered on your lawn.

"Although birds eat caterpillars, they're no match for hundreds of them on one lawn," Reeves said. "Look closer at the grass, and you may see several caterpillars munching on turf blades."

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ARMYWORMS marching through Georgia lawns can weaken turf and allow diseases to invade. "This year is the worst for caterpillars of all kinds that I've seen in 20 years," said Will Hudson, an Extension Service entomologist with the UGA College of Agricultural and Environmental Sciences.Birds eat the caterpillars, but when hundreds are present, homeowners need to treat to kill the worms. (Photo courtesy the UGA College of Agricultural and Environmental Sciences.)

Young armyworms are one-quarter to three-quarters of an inch long. Mature ones are one and a half inches. They are dark, with several light stripes down the length of the body. The head or "face" has an inverted Y on it.

The first battalion of females lays eggs in south Georgia. Succeeding generations march up the state, traveling on weather fronts and storms.

The caterpillars hatch from eggs in two to four days, depending on the temperature. Eggs develop to fully grown larvae in two to four weeks. The larvae burrow into the soil and form pupae. Moths emerge in about 14 days.

Fall armyworms can't overwinter in north Georgia. They may survive a mild winter in Florida and extreme south Georgia.

"They rarely kill grass," Reeves said. "But some plots may be severely weakened. Feeding damage, coupled with damage from the recent drought, may justify applying insecticides."

In turf or pastures, finding five caterpillars per square foot is a signal to start treating for fall armyworms.

If you suspect your turf is being infiltrated but can't find the caterpillars on the grass, use a soap flush to bring them to the surface.

Carbaryl (Sevin), chlorpyrifos (Dursban), acephate (Orthene), sinosyn (Conserve) and other insecticides are effective caterpillar killers.

Products containing Bt (Bacillus thuringiensis) are effective only on little (a half-inch or smaller) worms. Irrigate before treating, to move the caterpillars out of the thatch. Treat in late afternoon, when the caterpillars are likely to begin feeding. If possible, mow before you treat, and then don't mow for three days after the treatment.

For help in identifying armyworms, or for more information on treating them, contact the local Extension Service office.

Faith Peppers is the director of public affairs with the University of Georgia College of Agricultural and Environmental Sciences.