Fall armyworms are a problem in Alabama

In Southeast Farm Press

by Maggie Lawrence, Alabama Cooperative Extension System

Fall armyworms were found in millet in early June in western Mobile County, Ala. Armyworm caterpillars are detrimental to cattlemen and forage producers. The damage can seem to appear overnight.

Dr. Kathy Flanders, an Alabama Cooperative Extension System entomologist, said a fall armyworm caterpillar eats the most within its last feeding stage.

“Fall armyworm caterpillars consume around 80 percent of the total amount of food eaten during the last few days of the last feeding stage,” said Flanders. “They then burrow into the ground, and transform into a moth and the life cycle starts all over again.”

It takes about 30 summer days for a female fall armyworm to develop from an egg to the point where she is ready to lay an egg of her own. This is why early on it appears that the reports of damage come in batches about a month apart. Flanders said that it is especially important to scout forages the last week of June and the first week in July. Later in the season the new generations overlap. The moths are laying eggs almost every day, and all sizes of fall armyworm caterpillars can be found in any given field.

Control for fall armyworms is best done before they have molted into the last and largest size. A sweep net is a good inexpensive way to find fall armyworms when they are small. Most Alabama Extension county offices have a sweep net that you can borrow to look for fall armyworm caterpillars. If you find armyworms with a sweep net, follow up by checking to see how many caterpillars are present per square foot. If you find more than two caterpillars per square foot it is probably time to apply an insecticide, cut the hay or graze the affected forage.

You can find the latest map on where damaging populations of fall armyworms have been found, as well as helpful information related to fall armyworms online at “Fall Armyworm” section of the Insect Pest Management Page.

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