There are two species of asparagus beetles which attack and can cause economic damage to asparagus. They are the common asparagus beetle, Crioceris asparagi (Linnaeus), and the spotted asparagus beetle, Crioceris duodecimpunctata (Linnaeus).

Description:

The common asparagus beetle is 6mm (1/4 inch) in length, has a bluish-black head, legs and antennae tinged with green, a reddish thorax, and wing covers marked by yellowish patches and reddish borders. The larva of the common asparagus beetle is dark gray to olive-green with black legs and head. The spotted asparagus beetle is slightly larger and more robust than the common asparagus beetle. The adults are reddish-orange in color with black antennae, eyes and underside of the thorax. Each wing cover has six distinct black spots.

Damage:

Both the larvae and the adults of the common asparagus beetle damage the asparagus plants. The overwintered adults emerge and begin to feed on the tender growing tips of newly sprouted asparagus. They chew holes in the plant and cause a brownish discoloration of the tissue. The grubs will feed on the tender young tips and on foliage. The plant growth is seriously reduced and proper root development prevented, causing a decrease in the size and quality of the crop. The spotted asparagus beetle causes the most injury in the early season when the adults attack the growing tips and sometimes eat the buds of newly sprouted asparagus. The beetles also feed on foliage, eating out irregular areas. The larvae cause little damage because they feed inside the berries.

Life Cycle:

The adults of the common asparagus beetles overwinter in sheltered places such as piles of rubbish and heaps of old asparagus tops. The beetles emerge from their shelter and begin feeding on the tender tips of new shoots. They soon lay eggs on the young shoots. The eggs are elongate, oval, and deposited either singly or in rows of two to eight. Later in the season the eggs are laid on leaves and flower stems. The eggs hatch in three to eight days and the grubs begin feeding on the tender tips. When the grubs mature, they drop to the ground and construct a small earthen cell where they transform into pale yellowish pupae. The adult beetles emerge from the pupae. There may be two or more generations a year depending on the climate. The adult spotted asparagus beetles overwinter in piles of debris. They leave their winter quarters about one week later than the common asparagus beetles and begin to feed on the tender young shoots as well. They do not deposit eggs until the plant begins to blossom, about three weeks after emergence. The egg is deposited singly on plants, usually those bearing fruit. The egg is 0.5 mm (1/25 inch in length, olive brown, and attached to the leaf by one side. The larvae of the spotted asparagus beetle hatch in seven to twelve days and are yellowish-orange in color with a black head and legs. The larva finds a berry and enters it at the blossom end. Inside the berry it feeds on the seeds and it may attack three or four berries before it is mature. When fully grown, it drops to the ground by a silken thread and spins a cocoon just under the soil surface

Management:

Cutting the shoots very clean and just below ground level every day or two during the cutting season will tend to remove the eggs of the common asparagus beetle before the larvae can establish themselves in a home garden patch. In small gardens, gathering and destroying the asparagus berries will help to give control of the spotted asparagus beetle. Apply insecticides labeled for use on the asparagus beetles when the beetles first appear. Apply as frequently as needed but do not repeat applications within three days. Be sure to check the number of days to harvest before applying any pesticide to edible crops.

Adapted from the Cornell Cooperative Extension, 1999