By: Sandy Feather ©2010
Penn State Extension
Q. I planted an asparagus bed this spring. This is the first time I've grown asparagus, and I've been dismayed to see these small, dark, worm-like creatures eating the foliage. Can you tell me what they are and how I can protect my asparagus from them?
A. Asparagus beetles are the most common pests of asparagus in our area. There are two species, common asparagus beetle (Crioceris asparagi) and spotted (Crioceris duodecimpunctata). Common adults have reddish bodies with black stripes and cream-yellow patches on their wing covers. The worm-like creatures you noticed are the larvae. They are typically dark gray to olive green with black legs and head. The spotted asparagus beetle adult is reddish-orange with six black spots on each wing cover. The larvae are yellowish-orange with black legs and head.
Adults overwinter in garden debris, emerging as asparagus begins to grow in spring. They feed on the tender new tips and soon lay eggs on them. The larvae hatch in three to 12 days.
The larvae of common asparagus beetles feed on the foliage and stems while those of the spotted species prefer to feed in the berries of female plants. When grubs are mature, they move to the ground and build earthen cells where they pupate.
Control options include cutting the shoots off cleanly at the ground during the harvest season. This helps eliminate the eggs of common asparagus beetles before they build up a large population in the garden.
Gathering and disposing of the berries helps provide non-chemical control of spotted asparagus beetles. Handpicking the adult beetles and dropping them into a bucket of soapy water can be effective in small asparagus patches.
Be sure to clean up the asparagus patch thoroughly in the fall by cutting the plants to the ground after they have been killed by frost. Remove any summer mulch and re-mulch with fresh straw or shredded leaves. This eliminates many of the overwintering places for the adults. Pyrethrins and neem are plant-based insecticides that are labeled to control asparagus beetles and are approved for organic production. Conventional gardeners can use Sevin (carbaryl) to control these pests.