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UC Pest Management Guidelines


 Larva of fall cankerworm, Alsophila pometaria.

Apricot

Cankerworms

Scientific name:
Fall Cankerworm: Alsophila pometaria
Spring Cankerworm: Paleacrita vernata

(Reviewed 11/07, updated 11/07)

In this Guideline:


DESCRIPTION OF THE PESTS

Cankerworm larvae are typical of the group of worms called inch or measuring worms.Both fall and spring cankerworms are similar in appearance except that the spring cankerworm has two pairs of prolegs (legs located towards the end of the abdomen) whereas fall cankerworms have 3 pair with the pair furthest from the end being underdeveloped.

Cankerworms are greenish with three narrow, whitish stripes and one yellow stripe along the side of the body. When mature they are about 1 inch long, green to olive green, with stripes of a different shade of green along the sides. Cankerworms frequently stand on their posterior pair of prolegs in such a way that they resemble a small twig.

Fall cankerworms pass the winter in the egg stage on trees and hatch and feed on leaves in spring and summer. They pupate and develop into moths in fall. There is one generation per year.

Spring cankerworms overwinter in the soil as mature larvae and pupate in spring. Eggs are laid on bark and hatch somewhat later than those of fall cankerworm. Larvae feed on leaves later into the summer than fall cankerworms and then drop to the soil to pupate. There is one generation a year.

DAMAGE

In spring cankerworms occasionally cause damage in apricot.Larvae feed primarily on leaves, tending to skeletonize them. 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. Larvae can be found feeding throughout the tree but tend to be more numerous along center scaffold limbs.

MANAGEMENT

Cankerworms may be observed in spring when monitoring leafrollers during bloom. Bloom time treatments of Bacillus thuringiensis or spinosad 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.

Organically Acceptable Methods
Sprays of Bacillus thuringiensis, some narrow range oil formulations, and the Entrust formulation of spinosad are acceptable for use in an organically certified orchard.

Common name Amount/Acre** R.E.I.+ P.H.I.+
(trade name) (conc.) (dilute) (hours) (days)

  Calculate impact of pesticide on air quality
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 impact. Not all registered pesticides are listed. Always read label of product being used.
 
DELAYED DORMANT
A. NARROW RANGE OIL
  (Superior, Supreme) 4–6 gal 1–1.5 gal 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  . . . PLUS . . .
  SPINOSAD
  (Entrust)# 1.25–2.5 oz 0.3–0.6 oz 4 14
  (Success) 4–8 fl oz 1–2 fl oz 4 14
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: To avoid development of insect resistance, do not treat successive generations of the same pest with the same product.
  . . . OR . . .
  DIFLUBENZURON*
  (Dimilin) 2L 12 oz 3 oz 12 0
  MODE OF ACTION GROUP NUMBER1: 15
  COMMENTS: Apply in sufficient water to ensure good coverage. Apply with narrow range oil at 1.5% oil by volume.
  . . . OR . . .
  METHOXYFENOZIDE
  (Intrepid) 2F 10–16 fl oz 2.5–4 fl oz 4 7
  MODE OF ACTION GROUP NUMBER1: 18A
  COMMENTS: Do not apply more than 16 fl oz/acre/application or more than 64 fl oz/acre/season.
 
BLOOM
A. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates 4 0
  MODE OF ACTION GROUP NUMBER1: 11.B2
  COMMENTS: Treatments are timed by examining larval emergence from hibernacula. Treat when larva activity is detected by bud feeding or emergence from hibernacula and again 7-10 days later. This usually coincides with an application at the beginning of bloom and the second 7–10 days later, often full bloom to petal fall. In years when peach twig borer emergence is extended, make the second at 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 ft over the canopy using appropriate nozzles to allow better deposition on the tree tops. Precede this treatment with an oil spray during the delayed dormant season to control San Jose scale and European red mite eggs.
 
B. DIFLUBENZURON*
  (Dimilin) 2L 12 oz 3 oz 12 0
  MODE OF ACTION GROUP NUMBER1: 15
  COMMENTS: Include vegetable oil at the rate of 1 qt/acre. Do not apply after petal fall. Do not exceed 2 applications in any given season. Allow 21 days between applications.
 
C. METHOXYFENOZIDE
  (Intrepid) 2F 10–16 fl oz 2.5–4 fl oz 4 7
  MODE OF ACTION GROUP NUMBER1: 18A
  COMMENTS: Do not apply more than 16 fl oz/acre/application or more than 64 fl oz/acre/season.
 
 
**  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 label allows.
+ Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
* Permit required from county agricultural commissioner for purchase or use.
# Acceptable for use on organically grown produce.
Not recommended or not on label.
1 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 to help prevent development of resistance. 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 Group numbers are 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: Apricot
UC ANR Publication 3433
Insects and Mites
W. W. Coates, UC Cooperative Extension, San Benito County
R. A. Van Steenwyk, Insect Biology, UC Berkeley
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
K. R. Day, UC Cooperative Extension, Tulare County
K. A. Kelley, UC Cooperative Extension, Stanislaus County
J. L. Caprile, UC Cooperative Extension, Contra Costa County
Acknowledgment for contributions to Insects and Mites:
L. C. Hendricks, UC Cooperative Extension, Merced County

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