Description: Adult beetles are ¼ inch long with cream-colored markings over the metallic blue-black and red body.
Life Cycle: Adult beetles emerge from the soil in early spring and travel to new shoots where they feed and mate. Females secure up to 30 eggs, on end, to the tips of asparagus spears. Eggs are dark brown in color and positioned in rows. Larvae hatch in about one week and are 1/3 inch long. The larvae resemble slugs and are green to gray in color with black heads and legs. After feeding for a couple of weeks, larvae burrow into the soil and pupate. Within two weeks, adult beetles emerge and begin feeding. Beetles overwinter in plant debris. There are two generations of asparagus beetles each year.
Damage: Asparagus beetles feed on spears of asparagus as well as ferns. The black stain left behind the feeding larvae does not make asparagus inedible, but unsightly and perhaps undesirable. Leaves and tender buds near the growing tip are often damaged through feeding.
Control: Always begin with prevention in mind. Clean up plant debris at the end of the growing season to remove the overwintering habitat. During the active season, monitor plants regularly, primarily in the afternoon. Remove beetles/larvae/eggs by hand and place in a bucket of soapy water.
Horticultural oil and insecticidal soaps can be used for those who prefer organic methods of control.
Carbaryl (Sevin) and permethrin are two synthetic control options but note the wait time for harvest after application.