Native to North America, potato beetles, Leptinotarsa decemlineata are the largest pest threat to potato crops in the United States. These beetles quickly develop resistances to pesticides and so are very difficult to eliminate once a field is infested. Both the larvae and adult potato beetles feed on the leaves of the potato plant. They also may feed on other types of vegetables, such as tomatoes, tobacco, and cabbage.
Originally, the potato beetle fed on a wild plant called buffalo bur in the Rocky Mountains. When potato crops were introduced to the area, however, the beetles changed their main diet and began feeding primarily on the potato plants instead. The bugs quickly spread to other farmlands, soon covering the whole of the United States. The only places these insects are not found is in parts of Nevada, California, and Florida. These bugs can even be found in areas of Canada and have traveled overseas to infest crops in Asia and Europe.
About 0.5 inches (1.27 cm) long, potato beetles have distinctive black and yellow stripes running down their dome-shaped backs. Like many beetles, their backs appear to be a hard shell, but actually open into wings. The larvae is red with small black spots.
Potato beetle life cycles differ depending on the region, ranging from one to three generations in a year. Adults will spend the winter about one foot (0.3 m) below the surface in a potato field, emerging in spring to mate and eat. Eggs are laid in clusters on the underside of leaves. Clusters contain about 25 eggs, and a single female may lay up to 500 eggs total.
Once hatched, one larvae may eat as much as 15.7 square inches (40 cm2) in a single day. One adult eats approximately 19.5 square inches (50 cm2). Potato beetles can easily strip an entire potato crop of its leaves, which ultimately ruins the crop.
Several types of pest control options are available. Insecticides should only be used once to help prevent the beetles from developing a resistance, but even then are often not a reliable method to eliminate the pests. Genetically engineered potatoes help increase resistance to the bugs but are not allowed for any crop labeled organic.
Covering crops with thin fabric or edging a field with plastic also helps keep potato beetles from entering the field. Other options for pest control include introducing natural predators, such as spiders and lacewings, to control the population, as well as removing the top layer of soil in winter months to decrease ground temperature and kill the adults while they hibernate. In small home gardens, removing the larvae and adults by hand is the simplest way to eliminate an infestation.