Cucumber Beetles

Description of the Pest

The western spotted cucumber beetle and the western striped cucumber beetle occur throughout California. The other two species occur primarily in southern California. Cucumber beetles (also called corn rootworm beetles) overwinter as adults and are active beginning in early spring. Adults lay eggs at the base of plants. As soon as they hatch, larvae begin to feed on plant roots. They complete their development in the soil. There are about three generations a year.

Cucumber beetles are about 0.36 inch (1 cm) long and either have a greenish yellow back­ground with black spots or alternating black and yellow stripes. They fly readily and migrate into cultivated areas from alfalfa and other crops and from uncultivated lands.

Damage

Cucumber beetles feed on corn leaves, tassels, and silks. Damage is usually minimal. In some situations, larvae may cause serious injury by feeding on roots, and young plants can be killed or stunted.

Management

Cucumber beetles are attacked by a variety of natural enemies, the most important being a parasitic tachinid fly, Celatoria diabroticae. Treatment is rarely required to control cucumber beetles.