How to Manage Pests
UC Pest Management Guidelines
Scientific Name: Trichoplusia ni
(Reviewed 4/10, updated 4/10, pesticides updated 5/16)
In this Guideline:
Description of the Pest
Looper caterpillars can be distinguished from many other common caterpillars by their distinctive looping movement in which they arch the middle portion of their body to bring the prolegs or hind legs forward to meet the front legs. Loopers are green, usually with a narrow white stripe along each side and several narrow lines down the back. Loopers are smooth-skinned with only a few long bristles down the back; they may grow up to 1.5 inches long. Mature larvae spin silken cocoons and pupate, usually attached to leaves.
Adults are brownish moths with a distinctive silvery figure-8 on the front wings. Eggs are ridged and dome-shaped and usually laid singly on the undersurface of leaves. Loopers may have numerous generations and continue to develop all year long in California with the highest populations usually occurring in fall.
Cabbage loopers are foliage feeders but do not cause economic damage in eggplants.
Cabbage loopers have many natural enemies, and for that reason their presence at low population levels is considered beneficial in an eggplant field. These caterpillars are not usually treated for in eggplants.
Important parasites include the egg parasite Trichogramma pretiosum, the larval parasites Hyposoter exiguae, Copidosoma truncatellum, and Microplitis brassicae, and the parasitic tachinid fly Voria ruralis. A nuclear polyhedrosis virus disease is also important under certain circumstances; the bodies of diseased caterpillars turn into shapeless sacks of dark liquid and can often be spotted hanging from leaves.
UC IPM Pest Management Guidelines:
Insects and Mites
J. L. Aguiar, UC Cooperative Extension, Riverside County
Acknowledgments for contributions to Insects and Mites:R. H. Molinar, UC Cooperative Extension, Fresno County