The adult western corn rootworm is a yellow, 1/4-inch long beetle, with black stripes and a yellow underside. The adult northern corn rootworm is a greenish, 1/4-inch long beetle. The larva of each species is slender, white, and up to 1/2 inch long.
Adults feed on the green silks of sweet corn, preventing pollination and ear fill. They also damage cucumber and squash blossoms. Usually none of this adult damage is significant in commercial crops. The larvae feed on the roots of corn, reducing yield and causing stalks to fall over. This lodging can reduce yield if it occurs before pollination is complete.
Western corn rootworm has one generation per year. Eggs are deposited in the soil from mid-summer until autumn. Generally the eggs start hatching from late May to early June the mid-west. Larvae feed on corn roots. The larvae have three instars then pupate in the soil. Later larvae (mid June through mid July) tend to cause the most damage. During this same time, adult beetles begin to emerge. The males emerge before the females. Towards the end of July, females begin to lay eggs with greatest amount of egg laying occurring in first half of August. The beetles feed on pollen, green silks, or leaves.