How to Manage Pests

Pests in Gardens and Landscapes

Potato tuberworm—Phthorimaea operculella

Potato tuberworm larvae are dull white to pinkish and do not grow longer than 1/2 inch. They have dark heads. They are found tunneling in tubers, stems, fruit, or leaves.

Identification

Potato tuberworm can often be confused with tomato pinworm. Tomato pinworms may vary in color from gray to yellowish with red or purple around each segment. Pinworms are a problem only on tomatoes. They do not attack potatoes. Potato tuberworms can be distinguished by their dark heads.

Life cycle

Eggs are laid on tubers, foliage, plant debris, or soil. Moths will crawl through soil cracks to lay eggs on tubers beneath the soil. Worms tunnel into fruit or stalks or leaves.

Damage

In tomatoes, tuberworms burrow into fruit and into terminal stems, causing them to die. In potatoes, they tunnel into tubers, stalks, and leaves. Tuber eyes turn pink with excrement and silk.

Solutions

Damage to tomatoes, eggplant, or peppers can be avoided by not planting these crops near infested potato crops or following a potato crop in a garden. In potatoes, keep plants deeply hilled with soil when planting. Don't allow soil to crack. Sprinkler irrigation will help keep soil surface sealed. Harvest potatoes promptly. Destroy infested tubers or store them at temperatures below 52°F to prevent tuberworm development.

Adult potato tuberworm
Adult potato tuberworm

Potato tuberworm larva
Potato tuberworm larva

Tuber damage in potatoes
Tuber damage in potatoes

Damaged stem
Damaged stem


Statewide IPM Program, Agriculture and Natural Resources, University of California
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