Potato Tuberworm, Phthorimaea operculella
(Lepidoptera: Gelechiidae)

The potato tuberworm is distributed throughout the United States and is most common in southern areas, and particularly in the southeastern states. The transport of infested tubers causes extensive dissemination of this pest and results in reports of infestation where it does not normally exist. Many natural enemies are reported that affect the egg, larval, and pupal stages of potato tuberworm. Populations of the potato tuberworm are directly affected by weather patterns. Summers that are warm and dry tend to result in higher tuberworm populations. The life cycle generally takes from 15 to 90 days and about five generations occur annually. The potato tuberworm cannot withstand freezing so overwintering is difficult in cold climates. The egg is white and turns yellow with a distinct iridescence as they age. Larvae are white initially with a black head and may become pink or greenish-pink. Pupation occurs in the leaves or tubers of the plants. The pupa is initially white or yellow and eventually becomes mahogany in color. The adult is grayish-brown and the forewings are marked with dark spots.

The potato tuberworm feeds primarily on potato but other vegetable crops that may be infested include eggplant, pepper, and tomato. Some solanaceous weeds such as bittersweet, nightshade, groundcherry, horsenettle, and jimsonweed serve as alternate hosts. Damage caused by the potato tuberworm include leaf mining, stem mining, and tunneling of tubers. Populations of potato tuberworm can be determined in the field using sampling techniques such as pheromone traps, sticky traps, funnel traps, and water traps. Insecticides are often applied to the foliage to control tuberworm populations, and insecticide resistance may be a problem. Insecticides also interfere with natural enemies and should be taken into account before they are applied. Cultural control practices include crop rotation, sanitation, destruction of crop residue, deep planting of potato seed, and host plant resistance. Mass trapping using sex pheromones may also be used to reduce damage in the field.

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Potato tuberworm, Phthorimaea operculella, pupa in potato.
(University of Florida)

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