Colorado potato beetle is a key pest of potato and eggplant throughout the Northeast and requires a combination of cultural, biological and chemical strategies for effective control. For information on management and control of this pest please see our Colorado Potato Beetle, Management article.
Colorado potato beetles (CPB) are 1/2" long by 3/8" wide, oval with a rounded back, and each forewing is yellow with five black stripes. Eggs are bright yellow, elongated, laid in groups of up to 20-35 on the undersides of leaves. They may grow darker as they approach hatch. The larva is humpbacked, rusty-red with two rows of black dots along each side of its body, reaching about 5/8 inch long.
In the Northeast, CPB survives on solanaceous crops and weeds, including horsenettle, nightshade, eggplant, potato and tomato (primarily seedlings). CPB overwinters in the adult stage, primarily in soil (up to 12 inches deep) in the woods and brushy borders next to host crops, though some burrow into soil in the field. In spring the beetles search for food plants by walking from the field edges. Heavy feeding may occur on edges on non-rotated fields. If beetles do not find host plants via walking they will fly in search of food. Once host plants are found adults feed, mate and lay eggs. One female can lay up to 300 eggs. Eggs hatch in 7-10 days, depending on temperature. Feeding damage and larvae are easily seen on leaves. Larvae go through four molts (instars) before they pupate. In the first instar, the larvae are about the same size as the eggs and in the second instar they are about an eighth of an inch long. Mature, fourth instar larvae are hump-backed and plump, and reach 5/8" long before they drop to the soil and pupate. Adults emerge from pupae after 10-14 days leaving round exit holes at the soil surface. In southern New England there is second generation of eggs, larvae and adults, while northern New England there is one generation. Beetles fly out of fields in August, seeking overwintering sites at field edges.
Both adults and larvae cause feeding damage, but larvae damage is the most severe. Because the fourth larval stage (instar) does 85% of the feeding damage it is critical to control larvae while they are small. Potatoes can tolerate 20% defoliation (or even more, depending on time of the season and cultivar) without reduction in yield. Eggplant is more sensitive to damage and can only tolerate up to 15% defoliation before yield is affected.