How to Manage Pests
UC Pest Management Guidelines
Western Tussock Moth
Scientific Name: Orgyia vetusta
(Reviewed 11/09, updated 11/09, pesticides updated 9/15)
In this Guideline:
Description of the Pest
The western tussock moth is an occasional pest in coastal cherry orchards. Tussock moths survive the winter as fuzzy egg masses that female moths cement to their old pupal cases and cover with hairs. Mature larvae are gray caterpillars with numerous red, blue, and yellow spots and four white tufts of hair on their backs, two black tufts on their heads, and one on their tail ends. Larvae emerge in March and mature in May; when mature they are 0.5 to 1 inch long. Adults are active from May through July. Males are gray moths; females are grayish white and lack wings. Only one generation is produced each year.
Larvae are usually insignificant foliar feeders but may feed on the surface of fruit sufficiently in some years to warrant control measures. Feeding results in shallow, scabby, depressed areas at harvest.
Natural enemies usually keep tussock moth under control.
Natural enemies, including larval parasites (Hyposoter exiguae, H. fugitivus, Dibrachys sp.) and a predatory beetle (Trogoderma sternale), usually keep tussock moth under control.
Localized infestations can be pruned out and destroyed. Population buildups tend to be localized because the females are flightless.
Organically Acceptable Methods
Biological and cultural controls and sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are acceptable for use on an organically certified crop.
Monitoring and Treatment Decisions
Watch for tussock moth egg cases on leaves and twigs as you monitor orchards in spring before and during bloom. (For more information, see MONITORING PESTS AT BLOOM.) Begin to look for larvae in March. Infestations can be controlled with Bacillus thuringiensis while larvae are small. Petal fall sprays to control other worm problems generally control this pest. Later instars are difficult to control. Localized infestations can be pruned out and destroyed. This pest is cyclic and often controlled by parasitic wasps.
UC IPM Pest Management Guidelines: Cherry
Insects and Mites
J. A. Grant, UC Cooperative Extension, San Joaquin County
Acknowledgment for contributions to Insects and Mites:J. Colyn, Mid-Valley Ag. Services
M. Devencenzi, Devencenzi Ag. Pest Mgmt. and Research
P. McKenzie, Mid-Valley Ag. Services