Although there are many species of this pest, beet and fall armyworms are the most common species in the backyard garden. Beet armyworms are usually pale green in color with yellow stripes down the center of their backs and along their sides. Their heads have a distinct honeycomb pattern. Fall armyworms come in many colors, usually gray to yellow-green with stripes down their sides, and have a distinct inverted "Y" marking on their head. Both types of armyworms grow to a length of about 1 1/2 to 2 inches. The adult moths are a pale gray-brown color and usually lay their eggs in grasses and corn. Newly-hatched caterpillars have a looping or inchworm-like movement. Armyworms are common to the U.S. and Canada east of the Rocky Mountains.
Armyworms attack many garden crops, deciduous trees, and shrubs.
Armyworms are voracious eaters. As eggs hatch, caterpillars start feeding on grasses and stalks and then march on to other plants as they run out of food. Armyworms feed primarily at night or during overcast skies and can easily defoliate entire plants overnight.