Colorado Potato Beetle: the Key Pest of Potatoes

Colorado Potato Beetle in the Garden

The Colorado potato beetle, scientifically known as Leptinotarsa decemlineata, is the only serious pest of potatoes in our conditions. It takes full advantage of this monopoly and is capable of causing complete defoliation of plants. Total potato yields can be reduced by 30 - 50%. In addition to potatoes, it also attacks eggplant, tomatoes, and its entire development has been observed on wild-growing black nightshade and henbane.

Description of the Colorado Potato Beetle

Adult Colorado potato beetles are characterized by black and white longitudinal stripes on their wing covers and an orange head. They lay yellow-orange eggs in clusters, from which pink-red larvae with black heads and legs hatch. The larvae have two rows of black spots along the sides of their body.

Life Cycle of the Colorado Potato Beetle

Adult beetles overwinter in the soil, emerging in spring to search for potato crops or other host plants, where maturation feeding and mating occur. Female beetles then lay eggs, placing them on the underside of leaves in groups of several dozen, with one female capable of laying several hundred to several thousand eggs in her lifetime. Beetle larvae are very voracious and go through four developmental stages - instars. Fourth instar larvae leave the plant and burrow into the soil to pupate. In southern parts of Europe, the beetle has two generations per year, and some adults can overwinter twice even in our regions.

Control Options for Colorado Potato Beetle

Natural Antagonists of the Colorado Potato Beetle

Due to the relatively recent introduction of this pest, European ecosystems are not yet able to deal with it effectively. Pheasants, partridges and other bird species help eliminate the beetle, and from the insect kingdom, ladybugs, wasps, lacewings, and earwigs. Literature reports that the ground beetle Pterostychus cupreus consumes 10 second-instar larvae per day, while lacewings consume 10 first-instar larvae or 6 second-instar larvae. In the soil, both larvae and adults are attacked by entomopathogenic fungi and nematodes.

However, natural antagonists require greater biodiversity (species composition of plants and animals present) in the field and the absence of non-selective pesticides, which is difficult to achieve in today's potato monocultures.

How to Deal with the Colorado Potato Beetle

Growers can essentially deal with the Colorado potato beetle in two ways: mechanically or chemically.

• Mechanical Control

This involves spatial isolation of last year's and this year's potato fields and hand collection. Spatial isolation and crop rotation help reduce the number of beetles that reach the potatoes in spring, but this option is limited by the land available to the grower. For example, in an allotment garden where potatoes are grown every 20 meters, this effect cannot be utilized.

Manual collection involves gathering and eliminating beetles and their developmental stages. This is particularly important during the first feeding period of adult beetles after winter. At this time, by eliminating just a few individuals, considering their reproductive potential, you can prevent subsequent population explosion of Colorado potato beetles. You can also remove leaves with eggs, although these are difficult to spot on the underside of leaves.

• Chemical Control

Recently, strains of Colorado potato beetles have appeared that are resistant to organophosphates, synthetic pyrethroids and some other insecticides. Therefore, it is necessary to avoid using products from these groups, choose alternatives and, even better, combine them during the growing season to prevent further resistance development.

The most suitable time for treatment is during larval hatching, both in terms of their sensitivity and preventing feeding damage.