Peanuts and other crops including cotton, soybeans, wheat, etc. They are potential turf and pasture pests in late summer and fall. Large numbers can consume all above-ground plant parts, and they are capable of killing or severely retarding the growth of grasses.
Caterpillars or mature larvae are green, brown or almost black and about 1 and 1/2 to 2 inches long, with black and reddish brown stripes on each side of the body and four small, black spots on the dorsal side of each abdominal segment, with a marked pale, inverted "Y" on the front of the black head capsule.
Chewing on leaves from margins inward, ragged appearance on leaves. More pronounced in dry years and on Spanish peanut varieties. Fall armyworms are typically a problem on newly seeded winter wheat before a killing frost occurs. Young larvae will not chew completely through a leaf, creating a "window pane" effect. As they grow, they chew along the margins of leaves. Heavy numbers can completely destroy a planting. They are often more numerous along the edge of a field. They do not overwinter in Oklahoma, and we are reinfested each year by moths that migrate northward from Texas or Mexico, reaching Oklahoma by late June. Larvae are present by early July. There are several overlapping generations extending into October or even November in some years.
Larvae infesting a lawn can be detected by applying 1 tablespoon of pyrethrin in 1 gallon of water per square yard. The caterpillars will surface within a few minutes and can be found by separating the blades of grass. Treatment may be needed if 5 or more larvae are found per square yard. A variety of chemicals can be used for fall armyworm control, including the bacterial insecticide, Bacillus thuringiensis.