How to Manage Pests

UC Pest Management Guidelines

Apricot

Green Fruitworm

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

(Reviewed 10/14, updated 10/14)

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 numbers under control. However, regular monitoring each season is important so that prompt action can be taken if damaging levels develop.

Biological Control

Certain parasitic wasps (Cotesia (=Apanteles) ,Eulophus, Meteorus, and Ophion spp.) help keep green fruitworm numbers under control.

Organically Acceptable Methods

Use bloomtime sprays of Bacillus thuringiensis and spring sprays of the Entrust formulation of spinosad 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 numbers are present, prevent fruit damage by treating with insecticide. Delayed dormant applications of oil plus organophosphate insecticide control green fruitworms. Bacillus thuringiensis (Bt) 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.

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 (example formPDF).

Common name Amount to Use** REI‡ PHI‡
(Example trade name) (conc.) (dilute)
(hours) (days)

UPDATED: 10/14
Calculate impact of pesticide on air quality
The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Not all registered pesticides are listed. Always read the label of the product being used.
 
DORMANT and DELAYED DORMANT
 
A. NARROW RANGE OIL#
  (Supreme) 4–6 gal 1–1.5 gal 12 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Cover all parts of the tree. Oil alone will control low to moderate infestations. Do not use oil sprays on water-stressed trees. Some of the new lower-chilling varieties, especially Poppycot, can be highly susceptible to oil damage. Use extreme care when applying oil to these varieties. Check with certifier to determine which products are organically acceptable.
  . . . PLUS . . .
  DIAZINON*
  (Diazinon 50W) 1 lb/100 gal 4 days 21
  MODE-OF-ACTION GROUP NUMBER1: 1B
  COMMENTS: Organophosphate insecticide sprays are very toxic to honey bees. Apply diazinon only during dormant or delayed-dormant period if the cover crop or orchard floor weeds are not in bloom and attracting bees, and do not allow meat or dairy animals to graze in treated orchards. When applied early in the dormant season, this low-label rate provides effective control and reduces the risk of runoff into waterways, mitigating concerns of surface water pollution. Levels in surface waters of this material that are high enough to be toxic to some aquatic invertebrates have occurred following rains in January and February; avoid runoff into surface waters. Do not apply more than 4 lb product per application.
 
BLOOM
 
A. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates 4 0
  MODE-OF-ACTION GROUP NUMBER1: 11A
  COMMENTS: Make two applications during bloom: the first between popcorn and the beginning of bloom and the second 7 to 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 feet 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)# 1.25–2.5 oz 0.42–0.83 oz 4 14
  (Success) 4–8 fl oz 1.3–2.7 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; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. Apply in the late evening after bees have stopped foraging. Do not apply more than 29 fl oz/acre per year of Success or 9 oz/acre per 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; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. Apply in the late evening after bees have stopped foraging. Do not apply more than 28 oz/acre per year or make more than four applications per year.
 
C. METHOXYFENOZIDE
  (Intrepid 2F) 10–16 fl oz 2–4 fl oz 4 14
  MODE-OF-ACTION GROUP NUMBER1: 18
  COMMENTS: Do not apply more than 16 fl oz/acre per application or more than 64 fl oz/acre per season.
 
D. PHOSMET
  (Imidan 70-W) 2.125–4.25 lb 1 lb 7 days 14
  MODE-OF-ACTION GROUP NUMBER1: 1B
 
E. DIAZINON*
  (Diazinon 50W) 1 lb/100 gal 4 days 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. Do not apply more than 4 lbs product per application.
 
** For concentrate applications, use the amount given in 80 to 100 gal water/acre or lower if the label allows; for dilute application, amount is per 100 gal water to be applied in 300 to 400 gal water/acre, according to label.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) 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.
# 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 website at http://www.irac-online.org/.
* Permit required from county agricultural commissioner for purchase or use.

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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