POTATO TUBERWORM
The Potato Tuberworm (Phthorimaea operculella, family name Gelechiidae) is not considered a problem in the Northern California potato-producing areas, but it is under watch. In other areas, especially the Northwest, it can be a serious pest. The adult is a moth with a wingspan of 1/2 inch. At rest the moth has a slender appearance. It is gray colored with markings that are darker gray-brown or black. The tiny eggs are oval shaped, and range from white to yellowish. Larvae are caterpillars that vary in color from dirty white to gray, pink, or green when feeding on stems or leaves. They have a brown head and are just under 1/2 inch in length.

Damage
High numbers of Tuberworms on very young plants may result in stand reduction or stunted plants. The damage results from larvae tunneling in the tubers, which they enter at the eyes. Small deposits of frass can be seen with webbing around an eye where larvae have begun to tunnel. The tunnel appears dirty as it is filled with excrement.

Life Cycle
Female moths will lay eggs on tubers, foliage, or on the soil on a year-round basis if it isn’t too cold. They will even find crevasses in the soil to reach tubers to lay their eggs. The larvae hatch and enter the tubers, excavating tunnels. They will also go after foliage, even on tomatoes.