How to Manage Pests
UC Pest Management Guidelines
Scientific Name: Schizura concinna
(Reviewed 7/17, updated 7/17)
In this Guideline:
Description of the Pest
The redhumped caterpillar is easily recognized because of its striking appearance: the main body color is yellow and is marked by longitudinal reddish and white stripes. The head is bright red, and the fourth abdominal segment is red and enlarged. Redhumped caterpillars pass the winter as full-grown larvae in cocoons on the ground. In early summer, moths lay egg masses on the under surface of leaves. Eggs hatch into larvae that begin feeding on leaves. There are at least three generations each year.
Redhumped caterpillars skeletonize leaves, leaving behind only leaf veins. They form no webbing on the leaves.
A number of natural enemies attack redhumped caterpillar and often prevent it from becoming a destructive pest. Isolated infestations on small trees may be pruned out and destroyed. Occasional insecticide applications may be required on young trees.
Among the parasites that help prevent redhumped caterpillars from becoming destructive pests are two parasitic wasps, Hyposoter fugitivus and a species of Apanteles. The larvae of both parasites develop inside the caterpillar and pupate on the leaf surface in groups of silken cocoons. General predators include spiders, lacewings, bigeyed bugs, and damsel bugs.
Organically Acceptable Methods
Use biological control and sprays of Bacillus thuringiensis in an organically certified crop.
Monitoring and Treatment Decisions
Monitor for redhumped caterpillar during nut and shoot development.
Generally, control of redhumped caterpillar is only necessary on young trees. If 80 to 90% of the larvae in the second brood are parasitized, no insecticide application is necessary. However, if no parasitism is observed and four or more colonies are found per tree, an insecticide application is warranted.
Insecticide sprays applied for other pests often keep these leaf-eating caterpillars in check. If insecticide applications are required, all that is generally necessary are localized sprays with a handgun on individual trees when evidence of caterpillars is first observed.
UC IPM Pest Management Guidelines: Walnut
Insects and Mites
J. A. Grant, UC Cooperative Extension, San Joaquin County
Acknowledgment for contributions to Insects and Mites:W. J. Bentley, UC IPM Program, Kearney Agricultural Research and Extension Center, Parlier (Emeritus)
L. C. Hendricks, UC Cooperative Extension, Merced County (Emeritus)
W. H. Olson, UC Cooperative Extension, Butte County (Emeritus)
C. Pickel, UC IPM Program, Sutter and Yuba counties (Emeritus)
G. S. Sibbett, UC Cooperative Extension, Tulare County (Emeritus)
D. Light, USDA, Albany, CA (Emeritus)(Codling Moth)