Fall army worms march in Louisiana

Richard Bogren, Baldwin, Jack L.  |  1/4/2011 1:08:23 AM

News Release Distributed 08/20/10

Fall army worms are on the march in Louisiana, and heavy populations can cause significant damage to pastures, hay fields and lawns, according to LSU AgCenter entomologist Jack Baldwin.

“Fall army worms can have up to four generations per year in Louisiana, and each generation takes about a month to complete its life cycle from egg to adult moth,” Baldwin said. “In epidemic years, heavy moth flights can result in overlapping generations.”

The larval, or caterpillar, stage lasts two to three weeks, and the full-grown larvae are about 1-1.5 inches long, brown to green in color, with a prominent, inverted Y on the front of the head. They’re called army worms because they move together in large numbers, just like an army.

“Large caterpillars can eat most foliage in a field in just a few days,” Baldwin said. “If pastures are not scouted regularly, serious foliage damage from heavy infestations can suddenly appear.”

Farmers and ranchers can scout or sample for fall army worms in a field either with a sweep net or by visual inspection of 1 square foot of ground in several areas, he said. The economic threshold for well-managed pastures is one worm per sweep or one to two worms per square foot.

“Heavier populations can be tolerated if forage preservation is less critical, Baldwin said.” The insecticides recommended for fall army worms in pastures include Sevin, methyl parathion, Lannate and Tracer.

In urban areas, homeowners can treat their lawns when fall army worms threaten turf establishment or survival. “Bermuda grass would be the most susceptible,” Baldwin said. “Centipede and St. Augustine are less preferred but should still be considered at risk in an epidemic year.”

Insecticides included in the LSU AgCenter insect control guide for use on lawns include Acelepryn, Azatin XL, Battle GC, Mach 2, Lepinox WDG, Conserve SC, Talstar 10WP, Dylox, Condor XL, Crymax and Sevin.

Rick Bogren

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