ALABAMA A&M and AUBURN UNIVERSITIES
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contact Donna Reynolds, Extension Assistant Editor
Auburn, July 3---Hot, dry weather may lead to fall armyworm problems later this season, says Dr. Kathy Flanders, entomologist with the Alabama Cooperative Extension System.
"Biological control agents that help keep fall armyworm numbers down don't do well in these weather conditions," says Flanders.
The fall armyworm is a caterpillar about one and a half- inch long, varying in color from green to almost black. Each segment has four black spots on the back, arranged in a square near the end. On older caterpillars, there is a white inverted Y on the forehead.
"Fall armyworms feed on a variety of plants, including forage grasses. It's probably a good idea to keep an eye on hayfields and pastures. The more lush and well-fertilized a bermudagrass hayfield is, the more fall armyworms will like it," says Flanders.
The problem starts as a small brown patch in fields. Circular patches can reach 10-20 feet in diameter, according to Flanders.
"Once you see little patches of defoliation appearing, it may be the fall armyworms are still young enough to treat with insecticide," says Flanders.
Flanders adds that once the fall armyworms reach about three-fourths inch in length it's not economically feasible to control them. The only thing to do at this stage is salvage the forage by intensive grazing or mowing.
Flanders warns producers that another outbreak about a month after the arrival of the first fall armyworms may appear because of their life cycle. Check the field two or three weeks after the caterpillar is discovered for a new outbreak.
Producers who wish to scout for fall armyworm egg masses should look on the underside of tree branches, the underside of fence rails and sides of houses. Flanders says the eggs can be found in a patch as a yellowish mass. Look for caterpillars in the early morning or late evening: They don't usually feed in the heat of the day.
Flanders says one sign of infestation are brown ribbon- like remains of grass blades eaten almost all the way through on top of the still green, tougher leaf sheath. Another sign is frass, or insect excrement, scattered over the ground. Fall armyworm frass is about the size of bahiagrass seeds.