UC IPM: UC Management Guidelines for Western Tussock Moth on Plum

UC Pest Management Guidelines

Plum

Western Tussock Moth

Scientific name: Orgyia vetusta

(Reviewed 5/06, updated 5/06)

In this Guideline:

Description of the pest
Damage
Management

DESCRIPTION OF THE PEST

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.

DAMAGE

The caterpillars feed on foliage and young fruit, devouring large portions of leaves or entire leaves, and making irregular holes in the fruit.

MANAGEMENT

Natural enemies usually keep tussock moth under control.

Organically Acceptable Methods
Bacillus thuringiensis sprays and pruning out infestations are organically acceptable management methods.

Monitoring and Treatment Decisions
On small trees, cut out and destroy 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. The addition of a wetting agent to increase penetration of the webbing by the insecticide enhances control.

Common name

Amount to Use**

P.H.I.+

(trade name)

(conc.)

(dilute)

(days)

When choosing a pesticide, consider information relating to impact on natural enemies and honey bees, impact of timing on beneficials, and environmental impact.

BACILLUS THURINGIENSIS spp. KURSTAKI#

(various products)

Label rates

—

MODE OF ACTION: A microbial (Group 11.B2)¹ insecticide.

COMMENTS: Most effective on small caterpillars. Does not destroy natural enemies.

**	For dilute applications, rate is per 100 gal water to be applied in 300-500 gal water/acre, according to label; for concentrate applications, use 80-100 gal water/acre, or lower if the label allows.
+	Preharvest interval. Do not apply within this many days of harvest.
#	Acceptable for use on organically grown produce.
—	Not recommended or not on label.
¹	Modes of action are important in preventing the development of resistance to pesticides. Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode of action is assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.

UC IPM Pest Management Guidelines: Plum
UC ANR Publication 3462
Insects and Mites
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
K. R. Day, UC Cooperative Extension, Tulare County
Acknowledgment for contributions to the insects and mites section:
R. E. Rice, Kearney Agricultural Center, Parlier

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