Colorado potato beetles attack potatoes, peppers, tomatoes, and eggplants.
Adult Colorado potato beetles are about 1/2 inch long and yellow with brown stripes. The larvae are orange to red, with black spots, and can be 1/2 inch long when fully grown.
Damage Caused by Colorado Potato Beetles
Both the larva and adults eat the leaf margins and entire leaves of potatoes and other solanaceous plants, such as peppers, tomatoes, and eggplants and may defoliate plants.
Life Cycle of the Colorado Potato Beetle
Colorado potato beetles overwinter as adults in the soil and under debris. They become active in the spring as early potato plants emerge. Bright orange eggs are laid in clusters on the stems and foliage. The peak egg-laying periods occur in mid-June but may occur in May when the temperatures are high in early spring. Newly emerged larvae first feed on the younger leaves and later move on to older leaves. The larva pupates in the soil to the adult stage. The whole life cycle from egg to adult can occur in less than 3 weeks. Typically, two to three generations develop each summer in Illinois.
Management of Colorado Potato Beetles
Gardeners: Natural enemies rarely keep Colorado potato beetle in check, so where infestations occur, hand-picking and application of insecticides are the most common approaches to controlling this insect in home gardens.
- Rotate crops.
- Row covers can also be used to protect plants in smaller plantings.
Commercial: Crop rotation reduces and delays infestation in spring, locate field far away (700 to 800 yards) from overwintering sites.
- On young potato plants in the spring, control is probably warranted if feeding by adult beetles or larvae results in more than 20 to 30% defoliation (20 to 30% of the plant's leaf area is lost); this usually happens when more than 2 to 3 adult beetles are feeding on each plant.
- In the summer, when potato plants are blooming, some yield reduction is likely if defoliation exceeds 5 to 10%; this usually occurs when infestations exceed 5 larvae or 3-5 adults per plant.
- In addition to conventional insecticides, microbial insecticides that contain Bacillus thuringiensis tenebrionis can be used to kill Colorado potato beetle larvae. These microbial insecticides kill the target pest without killing other insects.
- Populations of Colorado potato beetle are resistant to one or more insecticides in some areas.
- If a registered insecticide fails to give control, switch to another insecticide in a different class.
- Do NOT retreat using a higher rate of the same insecticide.
Contact your county Extension office for current pesticide controls.