Damaging populations of fall armyworms have been found in 8 Alabama counties. While that is far fewer counties than last summer, it is important to check valuable forage grasses. Armyworm caterpillars are detrimental to cattlemen and forage producers. The damage can seem to appear overnight. Dr. Kathy Flanders, an Alabama Extension Entomologist, said that the 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 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. The moths lay eggs almost every day, and all sizes of fall armyworm caterpillars can be found in any given field.
Control armyworms before they molt into their last stage. If the armyworms are discovered early in the forage cutting cycle, Flanders said that producers should think about using the insecticides that have the longest residual on the foliage.
“No insecticide lasts forever, but three active ingredients with relatively long residual are Prevathon, Intrepid and Dimilin. These insecticides work better on small caterpillars,” said Flanders. “Producers should be aware that Dimilin only works when the caterpillar molts. The caterpillar keeps on eating until that time. Therefore, it is essential to apply Dimilin before the caterpillars have molted into their largest stage.”
Scouting for Armyworms
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, consider applying an insecticide, cutting the hay or grazing the affected forage.
The following counties have had reports of fall armyworms:
Lowndes Week of July 16
Pickens, Greene Week of August 6
Lee, Houston, Lawrence, Week of August 13
St. Clair, Elmore
You can find the latest map on where damaging populations of fall armyworms have been found here.
Featured and Article Image: Dr. Kathy Flanders
Here are some publications to help you:
Controlling Fall Armyworms on Lawns and Turf
Management of Fall Armyworm in Pastures and Hayfields
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