Colorado potato beetle

The Colorado potato beetle (Leptinotarsa decemlineata) has a well-deserved reputation as one of the most difficult agricultural pests to manage. It has developed resistance to every major class of insecticide introduced to control it over the last 150 years -- carbamates, organophosphates,.

The Colorado potato beetle (Leptinotarsa decemlineata) has a well-deserved reputation as one of the most difficult agricultural pests to manage. It has developed resistance to every major class of insecticide introduced to control it over the last 150 years — carbamates, organophosphates, pyrethroids, and neonicotinoids. In many commercial potato regions, almost no conventional insecticide provides reliable control because resistant populations are so widespread.

For the home gardener, this history is useful context: a conventional spray program that relies on a single insecticide class, applied repeatedly, will eventually fail. Understanding the pest's biology and diversifying management approaches is more effective than relying on any single chemical solution.

I don't grow potatoes at my Long Island property, so this guide draws on Cornell Cooperative Extension (which has done foundational research on this pest), Penn State Extension, and Clemson HGIC publications.

The pest

Leptinotarsa decemlineata is in the family Chrysomelidae (leaf beetles). Per Cornell Cooperative Extension:

• Adults: 8–12mm, oval, convex; bright yellow-orange with 10 black stripes on the wing covers; black and cream-colored markings on the pronotum (plate behind the head)
• Eggs: bright yellow-orange, oval, 1.5mm; laid in clusters of 20–50 on the leaf underside
• Larvae: hump-backed, red to orange with two rows of black spots on each side; grow through four instars from 1.5mm to 15mm

Host range: primarily potato and eggplant; also tomato, pepper, and some ornamental Solanum species.