Potato plants face many pests, no matter where they are grown. Some pests vary by climate, and gardeners should check with their local extension office to find out which pests are common to their area. Insect pests afflict all parts of the potato plant, from the leaves to the sap to the roots.
Flea beetles are so named because they are tiny beetles that jump around a lot, like fleas. There are several varieties that fall under this general heading; all are dark and measure between 2.5 and 3.5 millimeters long. Colorado potato beetles are slightly oval, and their most visible feature is the ivory and black stripes down their backs and across their wing cases. False potato beetles look similar, but are not a threat to potato plants. The best way to tell them apart is that false potato beetles have one ivory stripe missing toward the center of each wing case; it is replaced by a brown stripe.
Aphids are tiny green insects that suck the sap out of potato plant leaves, leaving the leaves sticky to the touch. They can usually be found on the undersides of the leaves. Leafhoppers are light green and leave some brown, burnt-looking leaf tips in their wake. This symptom of their presence is called hopperburn, and gardeners may be able to spot them by turning over leaves to catch them in the act.
Hornworms, wireworms, white grubs, European corn borers, potato tuberworms and vegetable weevils are all threats to the roots of potato plants. Hornworms are bright green with a horny protuberance on their heads and little stubby legs. Wireworms are light brown and very thin, as their name suggests; they have no legs. White grubs are fat, white, slimy, legless creatures. European corn borers are dark green with tiny little legs. Potato tuberworms range from white to light pink or green, and have legs. Vegetable weevils are pale green, have no legs and have somewhat blotchy heads. Root knot nematodes, more commonly known as tomato pests, can cause problems for potato plants as well. They invade the roots and lay their eggs, creating large knots on the roots. Unlike the other pests mentioned above, they are microscopic. Only their damage will be seen by the naked eye, and only then if the roots are dug up for examination.
Conventional solutions usually rely on strong insecticides tailored a particular insect infestation. Colorado potato beetles in particular can easily adapt to insecticides. Frequent alternation of insecticides is therefore necessary when these beetles are identified as the source of infestation. Conventional pesticides kill all insect life, not just pests—so potentially beneficial insects that feed on pest insects are killed as well. Organic solutions rely on restoring a natural balance of insect predators to areas where crops are grown. Beneficial nematodes hunt and eat the larvae of many underground insects before they can cause harm to potato plants. Unfortunately, they do not attack root knot nematodes. Encouraging lady beetles and spiders to go about their business can significantly reduce potato pests.
Conventional pesticides can be dangerous to humans, pets and other animals. If they are used, gardeners should make sure to follow the manufacturer's instructions to reduce the risk of ill effects.