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How to Manage Pests

UC Pest Management Guidelines

| More pests | More crops | About guidelines |

Larva of fall cankerworm, Alsophila pometaria.

Prune

Cankerworms

Scientific Names:
Fall cankerworm: Alsophila pometaria
Spring cankerworm: Paleacrita vernata

(Reviewed 6/06, updated 6/06)

In this Guideline:

DESCRIPTION OF THE PESTS

Cankerworm larvae have three pairs of prolegs. They are greenish above, with three narrow, whitish stripes and one yellow stripe along the side of the body; underparts are light green. Cankerworms frequently stand on the posterior pair of prolegs in such a way that they resemble a small twig. Cankerworms pass the winter in the egg stage. Caterpillars hatch and feed on leaves in spring and summer, then pupate and develop into moths in fall. There is one generation per year.

DAMAGE

The larvae are primarily leaf feeders, tending to skeletonize leaves. Occasionally they feed on young fruit by biting deep holes, which later heal, but leave large scarred depressions similar to the injury caused by green fruitworms.

MANAGEMENT

Bloom time treatments for peach twig borer will help to keep these leaf-eating caterpillars in check. If cankerworms are detected on small trees, infested twigs can be cut out and destroyed. View photos of caterpillars that are present at bloom for identification.

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 the timing on beneficials, and environmental impact.
 
BLOOM/POSTBLOOM
A. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates — 0
  MODE OF ACTION: A microbial (Group 11.B2)1 insecticide.
  COMMENTS: Make 2 applications during bloom: the first between popcorn and the beginning of bloom and the second 7–10 days later, but no later than petal fall. Compatible with fungicide sprays, and can be tank mixed with them. Good coverage is essential. Ground application using a concentrate rate (80–100 gal water maximum) is preferred. If aerial applications must be made because conditions do not permit ground application, a concentrate rate (5 gal or less) is preferred. Fly material on at a height of about 20 feet over the canopy using appropriate nozzles to allow better deposition on the tree tops.
 
 
**  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/.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

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 the insects and mites section:
W. O. Reil, UC Cooperative Extension Solano/Yolo counties

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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