Colorado Potato Beetle

Host Plants

Colorado potato beetles feed primarily on potatoes but also attack eggplant, peppers, and tomatoes (though less rarely).

Regions impacted

Found throughout North America and other temperate climates.

Description

Adults are hard-shelled, oval in shape, and grow to be about 3/8th of an inch long. They have black heads and a yellow-orange prothorax (the area behind the head) with 10 black stripes running lengthwise on their wing covers. Larvae are slug-like and about ½ an inch long. They are dark orange with a row of black spots along each side of their bodies. Eggs can be found on the undersides of leaves and are bright yellow ovals, standing on end in clusters of about two dozen.

Life Cycle

Adults overwinter 5–10 inches (12-25 cm) underground in harvested potato fields and gardens, emerging in spring to feed on young plants. Adults then mate, and females lay 10 to 30 eggs on the undersides of leaves. Each female can lay up to 500 eggs during her lifetime of several weeks. Eggs hatch in 4 to 10 days, depending on the air temperature. Hatchings are tiny larvae that feed on the leaves. Larvae can complete development in 10 days to 30 days, depending on the temperature. When fully developed, they drop from the plant, burrow into the soil and pupate. Adults emerge in 5 to 10 days in search of mates and, within 10 days, begin laying eggs. The cycle takes five to eight weeks per generation, and there are usually two generations per season in most areas.

Damage and Detection

Both adults and larvae feed heavily on the leaves of potatoes, tomatoes, eggplants, and other related plants. Feeding can kill small plants and reduce the yields of mature plants. The larvae are the most damaging, but adults also feed on foliage. Potatoes can usually tolerate up to 30 percent defoliation when in the vegetative state; however, they are much more sensitive when tubers are beginning to grow (and can tolerate no more than about 10% defoliation). Tuber bulking begins soon after flowering and is a critical time for beetle management.

Prevention and Control

Colorado potato beetles are best dealt with when they first appear in spring:

• Handpick or shake adults from plants.
• Crush any adults or, for the more squeamish, drop adults and larvae in a pail filled with soapy water.
• Inspect for eggs on the undersides of leaves and destroy them.
• Should you encounter egg clusters, pinch off the leaf and compost it.
• New adult beetles can fly into gardens, so regular inspection is recommended.
• Maintain a clean garden as weeds and other groundcover are alternative food sources. Adult potato beetles walk to find new host plants.
• Straw mulch spread around the foot of the plants gets underfoot and slows them down, as does a deep trench around the potato patch lined with slick plastic.
• In larger or regularly impacted gardens, grow potatoes under protective row covers.
• The Colorado potato beetle is resistant to most pesticides. As a last resort, consider spraying with neem.
• There are a few natural enemies of Colorado potato beetles: stink bugs and lady beetles will prey upon Colorado potato beetle eggs. Unfortunately, the impact of natural enemies has a modest impact on overall Colorado potato beetle numbers.