Colorado Potato Beetle

With the warm winter we have been experiencing, insects are likely to be more of problematic than usual. Colorado potato beetle is a huge problem in vegetable gardens and is hard to control. It is found in most regions of the country and feeds exclusively on the foliage of cultivated and wild plants in the nightshade (Solanaceae) family. It is a major pest of potatoes, eggplant, and tomatoes with alternate hosts of weeds such as horse nettle.

Colorado potato beetle overwinters in the soil as an adult and emerges about April to feast on potatoes, which is usually the first host plant during the cool spring temperatures. Female beetles may lay several hundred eggs in her lifetime, 30 to 60 at a time on the underside of plant leaves. The eggs hatch within four to nine days and start feeding immediately. The larva mature in two to three weeks before going in a pupal stage that last five to ten days before becoming adults in June. The higher the temperatures are, the faster the lifecycle completes.

Adults and larva feed on the foliage in the same manner, consuming large portions of the foliage. Large larva and first generation adults are the stages that do the most damage. They can completely defoliate the host plant and feed on the stems. Loss of foliage weakens the plant and results in a reduction of yield, whether it is tubers or fruit.

There are some biological control options but they are not effective on large populations. Spined soldier bug, two-spotted stinkbug, ladybird beetle, and carabid beetles are beneficial predators that prey on eggs and larvae. Crop rotation and thick straw mulch are cultural control measures that help. Since Colorado potato beetles have a high reproductive rate and they feed on only a few plants, they have the ability to become resistant to insecticides. Rotating chemicals with different modes of action helps prevent resistance.

(By Katie Kammler, MU Extension Regional Horticulture Specialist)