How to Manage Pests
UC Pest Management Guidelines
Scientific Name: Schizura concinna
In this Guideline:
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
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 treatments may be required on
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.
Biological control and sprays of Bacillus
thuringiensis are acceptable for use in an organically certified crop.
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 treatment is necessary. However, if no parasitism is observed
and four or more colonies are found per tree, a treatment is warranted.
Insecticide sprays applied for other pests often keep these leaf-eating
caterpillars in check. If insecticide treatments are required, all that is
generally necessary are localized treatments with a handgun on individual trees
when evidence of caterpillars is first observed.
||Amount to Use**
|The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies and
honey bees. When
choosing a pesticide, also consider information relating to environmental
||BACILLUS THURINGIENSIS ssp. KURSTAKI#
||MODE OF ACTION GROUP NUMBER1: 11.B2
||COMMENTS: Most effective on small caterpillars. Does not destroy natural enemies.
||MODE OF ACTION GROUP NUMBER1: 28
||COMMENTS: Larvicide. The best timing is to
apply before egg hatch. Do not
apply more than 0.2 lb a.i. (9 oz)/acre/year. Do not make more than four
applications per year. To reduce
the development of resistance do not make more than three consecutive
applications of any Group 28 insecticides (anthranilic diamide) per generation per season.
UC IPM Pest Management Guidelines: Walnut
UC ANR Publication 3471
Insects and Mites
C. Pickel, UC IPM Program/UC
Cooperative Extension, Sutter/Yuba counties
J. A. Grant, UC Cooperative Extension, San Joaquin County
W. J. Bentley, UC IPM Program/Kearney Agricultural Center, Parlier
J. K. Hasey, UC Cooperative Extension, Sutter/Yuba counties
W. W. Coates, UC Cooperative Extension, San Benito County
R. A. Van Steenwyk, Insect Biology, UC Berkeley
Acknowledgment for contributions to Insects and Mites:
W. H. Olson, UC Cooperative Extension, Butte County
L. C. Hendricks, UC Cooperative Extension, Merced County
G. S. Sibbett, UC Cooperative Extension, Tulare County
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