Western yellowstriped armyworm
Spodoptera praefica

This pest may be abundant in alfalfa fields in the Central Valley. The caterpillar is usually black, with two prominent stripes and many narrow bright ones on each side. At maturity it is approximately 1.5 to 2 inches long. Eggs are laid in clusters on the upper side of leaves and covered with a gray, cottony material. Eggs hatch in a few days and larvae reach full size in 2 to 3 weeks. Larvae pupate on or just under the soil surface. Adults are brown moths that primarily fly at night but may be encountered flying up as you walk through the field. There are at least five generations per year in the low desert and four generations in the Central Valley. This pest may be abundant at any time from June to early September.
Damage: Armyworms skeletonize leaves, leaving veins largely intact.