True Armyworm

Mythimna unipuncta

True armyworm on a sorghum plant
True armyworm on a sorghum plant. Photo courtesy of Ronald Smith. Licensed under CC BY 3.0.
Armyworm larvae are found throughout the United States east of the Rockies. They are an occasional pest of corn and small grains.
Armyworm larvae vary in color from green to brown. They have several stripes running the length of their body in various colors.
True armyworm larva
True armyworm larva. Photo courtesy of Frank Peairs, Licensed under CC BY 3.0.
Armyworm moths are a dull brown color. They have a wingspan of up to 1.5".
True armyworm moth
True armyworm moth. Photo courtesy of Whitney Cranshaw. Licensed under CC BY 3.0.
True armyworms feed on plant leaves, reducing the photosynthetic area and hence yield. They often hide in the whorl or at the base of the plant during the day. They are more commonly a problem in no till fields or fields with a late-killed cover crop.
Armyworms can be controlled with insecticides, although larvae hidden in the whorl are difficult to control. Always read and follow all label instructions.