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How to Manage Pests

Identification: Natural Enemies Gallery

Trioxys pallidus

Scientific name: Trioxys pallidus

Life stages of trioxys pallidus

Click on image to enlarge

Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Aphidiidae

Host: Walnut aphid on walnuts

Commercially available: No

DESCRIPTION      Life Cycle

This wasp was introduced to California from France for control of walnut aphid. Since its establishment in the late 1960s it has virtually eliminated the walnut aphid as a pest in most orchards, except when disrupted by broad-spectrum pesticides applied for other pests.

The adult wasp has a shiny black head and thorax and a long, slender, yellowish or orangish abdomen. The adult is roughly 2 to 3 mm (0.08–0.12 inch) long. Trioxys pallidus undergoes complete metamorphosis. The female wasp lays an egg inside aphid nymphs. The egg hatches into a larva, which consumes the inside of the aphid and pupates in the mummified aphid. The adult wasps emerge through a small exit hole. To monitor for Trioxys pallidus, look for aphid mummies.

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

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