Keep Potato Beetles Out of Your Garden

By Scout Nelson

Colorado potato beetles remain one of the most destructive pests for potato growers. These insects can quickly strip leaves from potato plants, reducing plant growth and lowering yields if they are not managed early.

Carrie Knutson, Horticulture Agent, NDSU Extension - Grand Forks County, explained that early scouting and regular inspections are the most effective ways to reduce Colorado potato beetle damage.

The beetle invasion can begin earlier than expected. In one example, adult beetles first appeared on June 22. Although adults and egg masses were removed every other day, a large number of larvae appeared in early July. The young larvae fed almost continuously and quickly removed leaves from several potato plants.

Colorado potato beetles spend the winter underground in gardens, fields, shelterbelts, and field edges. After emerging, adults feed, mate, and females lay clusters of bright orange eggs beneath potato leaves. A single female can produce around 350 eggs during her lifetime.

The eggs usually hatch within two weeks, depending on temperature. The larvae pass through four growth stages while feeding heavily on leaves. Young larvae are red, while mature larvae become pale pink before dropping into the soil to pupate and later emerge as adult beetles.

Potato plants can handle about 30% defoliation before flowering, but only about 10% defoliation after flowering when tubers are developing. For this reason, growers should inspect plants frequently and remove beetles before serious damage occurs.

Hand-picking adults, larvae, and egg masses remains one of the best control methods because Colorado potato beetles often develop resistance to insecticides. When insecticides are needed, they work best on young larvae but do not control eggs or pupae. Row covers and short-season potato varieties may also help reduce infestations.

Good fall cleanups are equally important. Removing potato vines, controlling nightshade weeds, and cleaning up other host plants such as tomatoes, peppers, and eggplants reduces the number of beetles that survive the winter.

Photo Credit: pexels-timmoor