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Colorado Potato Beetle

Leptinotarsa decemlineata

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Colorado potato beetles were once a pest of the west, but they migrated east by feeding on potato crops in the 1800's.
Colorado potato beetle

Colorado potato beetle

Scott Bauer, USDA ARS; (inset) Whitney Cranshaw, Colorado State University, Bugwood.org

Description: Colorado potato beetles are dome-shaped and measure just 3/8-inch long. Adults are yellow with 10 narrow black lines running longitudinally along their elytra. Larvae look similar to other beetle larvae - soft-bodied, with two rows of black dots along the sides. Colorado potato beetle larvae are brick red with black heads in the earliest instars. Eggs are yellow-orange and laid in clusters on the undersides of leaves.

Life cycle: Adult Colorado potato beetles overwinter in the garden soil, emerging in spring. Females lay eggs on the foliage of early crops of solanaceous plants, especially potatoes. First generation larvae feed for 10-30 days, dependant on temperatures. Fourth instar larvae drop to the ground and pupate in the soil, emerging as adults within 2 weeks. These adults will feed, mate, and reproduce as well. The second generation of adults feeds until fall, when they burrow into the soil for winter.

Crops damaged: Potatoes, tomatoes, peppers, eggplant. Both adults and larvae feed on foliage, stems, flowers, buds, and fruit of affected crops.

Signs and symptoms: If left unchecked, Colorado potato beetles can completely defoliate potato plants and other hosts. If you see signs of defoliation, check for beetle larvae. Late instar larvae cause the most damage to plants. Also, look at the undersides of leaves for clusters of yellow eggs.

Control measures:

  • Crush egg masses by hand.
  • Hand pick adults and larvae, dropping them in a can of soapy water to destroy them.
  • Use a barrier, such as cheesecloth, on young seedlings to prevent beetle damage.
  • Plant varieties that mature early to avoid damage by second generation beetles.
  • Attract beneficial insects, especially ladybugs and stink bugs, to prey on beetle eggs and larvae.
  • Apply Bacillus thuringiensis var. tenebrionis when larvae are young (first and second instars).
  • Weed the garden before spring adults emerge to eliminate food sources. Colorado potato beetles will feed on ground-cherry, jimsonweed, thistle, mullein, and horse nettle when potatoes or other garden crops are absent.

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