Colorado Potato Beetle
Leptinotarsa decemlineata (Say), Chrysomelidae, COLEOPTERA


DESCRIPTION

Adult - This oval, convex beetle is yellowish-brown and about 9 to 14 mm long. It has five longitudinal black stripes on each wing cover and a variable number of black spots on the pronotum (area just behind the head).

Egg - The yellow or orange elongated eggs are deposited on end and grouped into rows. Each egg is about 1.8 mm long.

Larva - Red at first, this soft grub has a black head and black legs. As it matures, the larva turns yellowish-red or orange and develops two rows of black spots along each side of the body. It reaches a length of about 10 mm.

Pupa - Generally resembling the adult in shape, the pupa is approximately 13 mm long.


BIOLOGY

Distribution - The Colorado potato beetle can be found throughout most of North America.

Host Plants - Colorado potato beetles infest a wide variety of plants including tomato, potato, eggplant, pepper, tobacco, ground cherry, nightshade, and other solanaceous plants.

Damage - Adult beetles and larvae feed on leaves and terminal growth of their host plants. The loss of foliage hinders development of tubers or fruit thereby reducing yield. In cases of heavy infestation, entire plants may be killed. Colorado potato beetle damage often occurs in isolated spots throughout the field.

Life History - Colorado potato beetles overwinter as adults in the soil. After emerging in spring, beetles feed for a short period before mating and laying eggs. Females each deposit 300 to 500 eggs in clusters of 20 or more on the undersides of leaves. Four to 9 days later, larvae emerge and feed for the next 3 weeks. Once mature, larvae drop to the ground and pupate in the soil. Five to 10 days later, a new generation of beetles emerge. In North Carolina, at least two full generations and a partial third occur each year.


CONTROL

Many cultural enemies help keep Colorado potato beetle populations low. Birds feed upon adults and larvae while predatory bugs attack eggs and larvae. These predatory bugs may be gray, brown, or brightly colored and are often shield-shaped. Two kinds of gray and black tachinid flies also parasitize larvae.

Katahdin potatoes show some resistance to Colorado potato beetles. Early treatment of commercially grown potatoes with systemic insecticides normally control overwintering beetles and early hatching larvae. However, some insect activity may persist around the field. The application of a foliar insecticide is not recommended until the first eggs have hatched. As soon as damage is noticed, treatment should begin. Chemical control is directed toward the first generation since the buildup of subsequent generations may cause severe damage and defoliation. In some cases, spot treatments may be effective. For recommended insecticides and rates, consult the current North Carolina Agricultural Chemicals Manual.

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