How to Manage Pests
UC Pest Management Guidelines
Western Tussock Moth
Scientific Name: Orgyia vetusta
In this Guideline:
The full-grown western tussock
moth larva is 1.5 to 2 inches in length, generally gray in
color with numerous colored spots, four prominent white tufts of hair on its
body, and two black tufts on its head and one on its posterior end. The adult female moth is wingless and light silver-gray. Males are
winged and also gray in color. Larvae appear in spring and become adults in
May, June, and July. These adults produce caterpillars that feed for 40 to 60
days before they pupate. There are two generations of tussock moth in
southern California, but only one in northern California.
Western tussock moth caterpillars
feed on foliage and young fruit, devouring large portions of leaves or entire
leaves, and making irregular holes in the fruit.
Natural enemies usually keep
tussock moth under control.
Bacillus thuringiensis sprays and pruning out infestations are
organically acceptable management tools.
and Treatment Decisions
On small trees, remove infested
twigs. Spray programs for other insects generally reduce populations. If
insecticide treatments are required, localized treatments on individual trees
and branches are generally all that is necessary. Treat when small caterpillars
are first observed. To identify caterpillars that are
present during bloom. The addition of a wetting agent to increase penetration of the webbing by the
insecticide enhances control.
||Amount to Use**
|When choosing a
pesticide, consider information relating to impact
on natural enemies and honey bees, impact of the timing on beneficials, and environmental impact Not all registered pesticides are listed. Always read label of product being used.
||BACILLUS THURINGIENSIS ssp. KURSTAKI#
||MODE OF ACTION GROUP NUMBER1: 11.B2
||COMMENTS: Most effective on small caterpillars. Does not destroy natural enemies.
UC IPM Pest Management Guidelines: Prune
UC ANR Publication 3464
Insects and Mites
C. Pickel, UC IPM Program, Sutter/Yuba counties
F. J. A. Niederholzer, UC Cooperative Extension, Sutter/Yuba counties
W. H. Olson, UC Cooperative Extension, Butte County
F. G. Zalom, Entomology, UC Davis
R. P. Buchner, UC Cooperative Extension, Tehama County
W. H. Krueger, UC Cooperative Extension, Glenn County
Acknowledgment for contributions to Insects and Mites:
W. O. Reil, UC Cooperative Extension Solano/Yolo counties
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