The adult is a small, mottled gray or dusky winged moth. The caterpillars become full grown in about 2 to 3 weeks and are about 1.25 inches long. They may be olive green to almost black in color with a yellow stripe on each side of the body. Beet armyworms may become abundant and cause severe injury to asparagus ferns in summer and fall. The adult is a small, mottled gray or dusky winged moth.
Larger larvae feed on the epidermis of the branches of the ferns.
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. Armyworm eggs and larvae are easier to find on weeds near asparagus fields than in the fields when the ferns are large. Monitor fields twice weekly because populations can build quickly. Adult beet armyworm activity can be monitored by using pheromone traps placed along the edges of fields.