Egg - The dark brown, bullet-like egg of the common asparagus beetle is about 1.5 mm long and attached by one end to the host plant. The spotted asparagus beetle egg is greenish and glued on its side to the host plant.
Larva - The larvae of both species are plump, humpbacked, wrinkled, sluggish, and about 9 mm long when fully grown. The dark gray larva of the asparagus beetle has a black head and black distinctly fleshy prolegs; that of the spotted species varies from pale yellow when newly hatched to orange when mature.
Pupa - The yellowish pupa is protected by a tough silken cocoon embedded with soil particles.
Host Plants - Asparagus is the only food plant of these beetles.
Damage - As soon as asparagus shoots appear in spring, they may be attacked by asparagus beetles. The beetles eat shoot and leaves but are particularly damaging when they gnaw the tips of buds causing them to scar and turn brown. In dry seasons, asparagus shoots may be blackened by hundreds of eggs from these beetles. The larvae of the common asparagus beetle damage plants much like the adults but also secrete a black fluid which stains the plant. Larvae of the spotted species, on the other hand, feed on developing berries, each larva often consuming three or four. Damage to the berries, however, is of little economic importance.
Life History - Asparagus beetles overwinter as adults in sheltered sites, particularly under bark or in stems of old plants. Common asparagus beetles appear slightly earlier in spring than the spotted species. The beetles feed as soon as they emerge and several days later egg laying begins. Eggs hatch 3 to 8 days later depending on temperature. For 10 to 14 days, larvae feed and develop through four instars. Fully grown larvae crawl to the ground and dig chambers in the soil. Within the chambers, they spin silken cocoons and pupate for 5 to 10 days. Soon afterwards a new generation of beetles emerges.
This 3- to 4-week cycle is typical in the summer. In fall or early spring, 8 weeks may pass from the egg to the adult stage. As many as five generations per year occur in North Carolina.
In small gardens, larvae can be knocked from plants onto the soil. The larvae usually are unable to reclimb the plants and die on the hot soil. In the case of the spotted asparagus beetle, gathering and burning asparagus berries helps lower and prevent further infestations.
Should populations of this pest become a problem, chemical controls are available. For up-to-date recommendations, consult the current North Carolina Agricultural Chemicals Manual.
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