Corn rootworms have long been the major economic pests of corn in the United States. In the American Midwest, corn rootworm damage has been sporadic. Over the past several years, however, the invasion of western corn rootworms and the expansion of northern corn rootworm populations in the state have greatly increased the potential for economic losses.

The adult is the only developmental form of northern and western corn rootworm that can be distinguished visually without the aid of a microscope. Adult northern corn rootworm beetles are only about ¼ inch long and are solid yellowish green (tan when newly emerged). Western corn rootworm beetles are about the same size and color, but they have three dark stripes on their wing covers. On some beetles the stripes overlap, making the wings appear dark brown or black. Adults are very active and fly rapidly if disturbed.

The spherical, whitish or yellowish eggs are deposited in the soil and are almost impossible to see. Larvae of both species are white, measure about 1/8 to 1/2 inch long, and have brown heads, six small forelegs, and slightly wrinkled skin. Larvae also have a dark plate on the top side of the last abdominal or tail segment. The pupae are white, but otherwise similar in appearance to the adult.