Colorado Potato Beetle

Adults are rounded, roughly one centimetre long, and yellow-orange with ten black longitudinal stripes running down the wing covers. Larvae are humpbacked, orange-red to pink, with two rows of black spots along each side of the body and a dark head. Eggs are bright yellow-orange and laid upright in tight clusters on the undersides of leaves.

• Adults: yellow-to-orange beetles about 1 cm long with ten black stripes along each wing cover
• Larvae: humpbacked, orange-red to pink grubs with two rows of black spots along each side and a black head
• Eggs: bright yellow-orange, laid upright in clusters on the undersides of leaves

Adults overwinter in soil, often near the previous year's host plantings, and emerge in spring as host plants become available. After feeding and mating, females lay clusters of eggs on the undersides of leaves. Larvae pass through four progressively larger instars, feeding heavily throughout, before dropping to the soil to pupate. Depending on climate and the length of the growing season, one to several generations can occur in a single year.

Egg

Laid in upright clusters on leaf undersides; hatching is faster in warm weather.

Larva (four instars)

Increasingly large, humpbacked stages that feed heavily on foliage before dropping to the soil.

Pupa

A non-feeding stage in the soil during which the adult form develops.

Adult

Emerges from the soil to feed and mate, and, in temperate regions, later overwinters.

Both larvae and adults chew foliage, and heavy populations can strip plants of leaves entirely — a process known as defoliation. Defoliation reduces the plant's capacity for photosynthesis and can significantly affect tuber yield if it occurs during critical growth stages. The beetle's primary host is potato, but it also feeds on other solanaceous plants, including tomato, and on related solanaceous weeds.

Regular field scouting for eggs, larvae, and adults — especially early in the season, as overwintered adults colonize emerging plants — allows management decisions to be made before defoliation becomes severe.

• Inspect leaf undersides for egg clusters and young larvae
• Scout field edges first, where colonizing overwintered adults often concentrate
• Track larval instar stages, since later instars cause most of the defoliation
• Compare counts or defoliation levels against locally established thresholds

Because of its history of resistance, Colorado potato beetle management relies on combining several tactics rather than repeated use of any single insecticide.

• Rotate potato plantings away from the previous year's fields where practical, to delay colonization by overwintered adults
• Conserve natural enemies such as predatory stink bugs and ground beetles
• Use physical barriers, such as trench barriers or row covers, where feasible
• Monitor populations closely and, where any insecticide is used, follow guidance on rotating modes of action to slow further resistance development