Potato plants throughout the US may come under attack from a variety of leaf-eating insects. Most of the foliage growth has occurred by the time large infestations appear, and potato plants can withstand up to 30% defoliation without tuber production suffering. The unsightly damage to potato plants in the home garden can be controlled organically by using row covers or by dusting plants with the bacterium, Bacillus thuringiensis (Bt).
Colorado Potato Beetle, Adults and Larvae
Colorado potato beetles are the most destructive leaf-chewing insects that attack potato plants. They cause losses to commercial crops if they are not controlled. Both larvae and adults eat the foliage of potato plants, stripping the foliage until mid-veins and stems remain. When conditions are right for the emergence of potato beetles, they appear almost overnight. The damage is swift.
Plastic-lined trenches surrounding the potato field are an organic method of trapping these beetles. Curiously, the potato beetles can walk on bare plastic mulch, but when plastic mulch is covered with a light layer of soil, they cannot walk on it. Plastic trench methods can cut the beetle population in a field by half, reducing the need for other controls. Predator insects that feed on the potato beetle larvae are also effective in reducing the surviving beetle populations.
Flea beetle damage can be recognized by the small holes the adult insects make in potato plant leaves. The holes are scattered over the foliage, resembling shot holes. The worst damage may be from the larvae of these beetles, which live in the soil. They burrow into the potato tubers, leaving tunnels just under the skin of the tubers. This opens the tuber to bacteria, fungus and rot diseases, which can damage the crop.
Blister beetles are between 3/4 inch and 1 1/2 inches long. They are predominately found in potato fields near rangeland or desert areas where their larvae winter over. They are not a commercial threat to potato crops, and control is not typically used against them. Blister beetle adults eat potato foliage, causing raggedy looking leaves. The damage usually does not affect the plant's production.