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How to Manage Pests

UC Pest Management Guidelines

Potato tuberworm larva.


Potato Tuberworm

Scientific name: Phthorimaea operculella

(Reviewed 1/07, updated 1/07)

In this Guideline:


Potato tuberworm infestations are not common in California, but when they do occur it is most often on the coast and in the southern San Joaquin Valley. Serious infestations are almost always associated with potato culture. Where tomatoes follow potatoes and where there are volunteer potato plants, there is always the danger of a serious infestation. Larvae of the tuberworm, when fully grown, are pinkish gray, with a brown head and prothoracic shield.


Potato tuberworm larvae prefer to enter the fruit at the calyx end, making a dry burrow through the core and the fleshy portions that radiate from it, but they may enter at any point on the fruit's surface. They usually spin a web over the entrance to their burrows, and the fruit must be carefully observed to detect damage.


No control guidelines at this time other than to avoid planting tomatoes after or near infested potato fields or cull piles.


[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Tomato
UC ANR Publication 3470
Insects and Mites
F. G. Zalom, Entomology, UC Davis
J. T. Trumble, Entomology, UC Riverside
C. F. Fouche, UC Cooperative Extension, San Joaquin County
C. G. Summers, Entomology, UC Davis/Kearney Agricultural Center, Parlier
Acknowledgments for contributions to the insects and mites section:
N. C. Toscano, Entomology, UC Riverside

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