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UC Pest Management Guidelines


Speckled green fruitworm larva feeding on leaf.

Apricot

Green Fruitworm

Scientific Names:
Orthosia hibisci, Amphipyra pyramidoides, Xylomyges curialis, and others

(Reviewed 11/07, updated 2/09)

In this Guideline:


DESCRIPTION OF THE PESTS

Larvae are pale green caterpillars, often with whitish stripes down each side of the body and a narrow stripe down the middle of the back. The adult of one common species is a grayish moth with a 1-inch wingspan. Most species overwinter as adults and have one generation each year.

DAMAGE

Green fruitworms eat large holes in young leaves and fruit.

MANAGEMENT

Dormant treatments and bloomtime applications for other pests help keep fruitworm populations under control. However, regular monitoring each season is important so that prompt action can be taken if damaging populations develop.

Biological Control
Certain parasitic wasps (Apanteles, Eulophus, Meteorus, and Ophion spp.) help keep green fruitworm populations under control.

Organically Acceptable Methods
Bloomtime sprays of Bacillus thuringiensis and spring sprays of the Entrust formulation of spinosad are acceptable on organically grown apricots.

Monitoring and Treatment Decisions
Monitor for green fruitworms from the beginning of bloom until after petal fall. Carefully check young leaves and blossoms for the presence of larvae and leaf damage. Use a beating tray to catch larvae that drop from the tree as you shake blossom clusters, young fruit, and foliage, or hit limbs with a beating stick. Check green fruit for the presence of larvae. A treatment threshold of 1 worm per 100 fruit clusters per 20-acre block or 1 worm per 50 beat tray samples has been developed for pears and probably is applicable to stone fruits.

If damaging populations are present, prevent fruit damage by treating with insecticide. Bacillus thuringiensis formulations are safe to use during bloom and are effective on small larvae. Bloomtime applications of Bt for peach twig borer may control green fruitworms and cankerworms as well. If you use other materials, make applications during or shortly after petal fall. Spot-treat localized infestations. Continue to monitor for the pest after treatment. If you find no more young larvae, you need take no more control action that season. Delayed dormant applications of oil plus organophosphate insecticide control green fruitworms.

Take a fruit damage sample at harvest to assess the effectiveness of the current year's IPM program and to determine the needs of next year's program (see FRUIT SAMPLING AT HARVEST). Record results (sample form115 KB, PDF).

Common name Amount to Use** 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 in to 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.
 
BLOOM
A. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates 4 0
  MODE OF ACTION GROUP NUMBER1: 11.B2
  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. 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. Compatible with fungicide sprays, and can be tank mixed with them. For tank mixes, observe all directions for use on all labels, and employ the most restrictive limits and precautions. Never exceed the maximum a.i. on any label when tank mixing products that contain the same a.i.
 
PETAL FALL and AFTER
A. SPINOSAD
  (Entrust)# 1.71–2.5 oz 0.43–0.6 oz 4 14
  (Success) 6–8 fl oz 1.5–2 fl oz 4 14
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: Most effective when applied at petal fall. This product is toxic to bees for 3 hours following treatment; apply in the late evening after bees have stopped foraging. Do not apply more than 29 fl oz/acre/year of Success or 9 oz/acre/year of Entrust.
 
B. SPINETORAM
  (Delegate WG) 4.5–7 oz 1.125–1.75 oz 4 14
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: This product is toxic to bees for 3 hours following treatment; apply in the late evening after bees have stopped foraging. Do not apply more than 28 oz/acre/year or make more than 4 applications/year.
 
C. METHOXYFENOZIDE
  (Intrepid) 2F 8–16 fl oz 2–4 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.
 
D. PHOSMET
  (Imidan) 70WP 4.25 lb 1 lb 3 days 14
  MODE OF ACTION GROUP NUMBER1: 1B
 
E. DIAZINON* 50WP 3 lb 1 lb 24 21
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Avoid drift and tailwater runoff into surface waters. Where apricots are grown adjacent to waterways, do not use this material.
   
** For concentrate applications, use the amount given in 80-100 gal water/acre or lower if the label allows; for dilute application, amount is per 100 gal water to be applied in 300-400 gal water/acre, according to label.
+ 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.
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/.

IMPORTANT LINKS

[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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