Asparagus Beetles: Good or Bad for the Garden?

Asparagus beetles, naughty, nice or neutral? The asparagus beetle is aptly named for its fondness of part of the asparagus plant.

| June/July 2003

Learn all about asparagus beetles.

These two closely related beetles are similar in size, 1/4-to 1/3-inch long, but they have slightly different appetites for asparagus plants. Both can bear a minimum of two generations during each growing season and, in warm climates, up to five generations.

The asparagus beetle, Crioceris asparagi, is the most likely to eat the plant part that the human gardener also relishes. Overwintering as an adult, this bug bears four white or yellowish spots on its wings, is reddish underneath and on the wing edges, and has a dark-red thorax. Noticeable antennae run half the body's length.

In early spring, just as the asparagus is breaking the surface, the adult beetles emerge, hungry from overwintering in plant debris. They begin feeding on the earliest spears and soon mate. The females lay tiny, dark, linear eggs on the asparagus at right angles to the foliage. Adults dine on the main spears; grey/green-colored larvae feed on the lighter foliage.

Indentations caused by the feeding are brown in color and will decrease the vigor and size of the spear. Severe feeding weakens the root system, reducing the plant's vigor.

The spotted asparagus beetle, Crioceris duodecimpunctata, is as pretty a bug as you would ever want to see. In the western United States, this beetle is bright pumpkin orange with tiny black dots on its wings — reminiscent of a Mayflower moving van; in other areas, this beetle can be red or dark red. The antennae also measure about half its body length.

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