Asparagus is the only food plant of this beetle.
As soon as asparagus shoots appear in the spring, they may be attacked by asparagus beetles. The beetles eat shoots and leaves but are particularly damaging when they gnaw the tips of buds, causing them to scar and turn brown. The larvae damage plants much like the adults but also secrete a black fluid which stains the plants. The eggs are glued to the plants and are difficult to remove from harvested spears.
Asparagus beetles overwinter as adults in sheltered sites, particularly under bark or in stems of old plants. Beetles emerge in early April and begin to feed. Egg laying begins in mid or late April. Eggs hatch in 3 to 8 days and larvae feed for 10 to 14 days. Pupation is in silken cocoons in chambers in the soil and lasts 5 to 10 days. This 3- to 4-week life cycle is typical of the summer but a generation can take as much as 8 weeks in early spring or late fall. There are probably four or five generations per year.
The adult beetle is smooth, shiny, slightly elongated, and slightly over 1/4 inch long. It has a metallic blue head and bluish-black wing covers, each with three yellowish, squared spots and a red outer margin. The thorax is reddish with two small blue spots. The eggs are elongate, dark brown in color, and attached by one end to the host plant. Larvae are plump, humpbacked, wrinkled, and sluggish. They are dark gray in color with black heads. To date, only 7 counties have reported the occurrence of this pest. However, it is expected to continue to spread through the state.
Please contact your local county extension office for current information.