How to Manage Pests

UC Pest Management Guidelines

Apricot

Peach Twig Borer

Scientific name: Anarsia lineatella

(Reviewed 11/07, updated 2/09)

In this Guideline:


DESCRIPTION OF THE PEST

The peach twig borer is widely distributed throughout California and is found on several hosts. The adult moth is about 0.3 to 0.5 inch long, with steel gray, mottled forewings. Young larvae are almost white with black heads. Mature larvae are about 0.5 inch long and have black heads and dark brown bodies with white portions between each body segment, giving the appearance of stripes. The peach twig borer overwinters as a larva in a tiny cell called a hibernaculum, located in limb crotches of 1- to 4-year-old wood or in roughened areas of the trunk. There may be three to four generations each year, but the later generations occur after apricot harvest.

DAMAGE

This pest damages in two ways. Larvae burrow down tender shoots and kill the tip, which may cause problems in training young trees. They also feed on fruit, primarily at the stem end (early harvested varieties are less susceptible than later harvested ones). Either feeding damage or the presence of larvae will cause a fruit to be offgrade.

MANAGEMENT

Within an IPM program, the preferred management strategy for peach twig borer is well-timed treatments of environmentally sound insecticides around bloom time. These include Bacillus thuringiensis, spinosad (Entrust, Success), and diflubenzuron (Dimilin). Bloom time applications integrate well with brown rot treatment, thus helping to cut application costs. Bloom sprays are preferred over in-season sprays in an IPM program because they have less adverse impact on beneficials and nontarget organisms and do not leave residue on fruit.

Alternatively, peach twig borer can be controlled with a dormant spray of an organophosphate or pyrethroid insecticide plus oil to kill overwintering larvae in the hibernacula; however, these sprays pose water quality concerns and may pose some risks to raptors, aquatic invertebrates, beneficials, and other nontarget organisms. Dormant sprays of oil plus spinosad (Entrust, Success) or diflubenzuron (Dimilin) do not present these environmental problems. Dormant sprays of oil alone or oil combined with an insecticide, however, have the advantage of controlling some other stone fruit pests, especially mites and San Jose scale. (Oil alone does not control peach twig borer.) Mating disruption can also be used effectively in early harvested orchards to supplement dormant sprays.

Mating disruption

Mating disruption with sex pheromones can be used to supplement dormant or bloom time sprays. The main practical use for mating disruption is where the crop is harvested before July and in organic systems. For later harvested fruit, mating disruption has not been reliable against peach twig borer when used alone and should be supplemented with a bloom treatment of Bacillus thuringiensis or spinosad.

Mating disruption is most effective in orchards with low moth populations that are not close (a mile) to other untreated peach twig borer hosts or almond orchards. Efficacy is reduced by small orchard size (especially if located near outside sources of moths; if a small orchard is isolated, then size is not a major factor), uneven terrain, reduced pheromone application rates, applying too low in the tree, improper timing, and high insect pressure. Follow timing guidelines given in the treatment table below.

Biological Control

Peach twig borer has about 30 species of natural enemies. The gray field ant, Formica aerata, preys on peach twig borer during spring and summer. In some years these natural enemies destroy a significant portion of larvae, but by themselves they generally do not reduce twig borer populations below economically damaging levels. Other commonly found natural enemies in California are the chalcid wasps, Paralitomastix varicornis and Hyperteles lividus, the braconid wasp Macrocentrus ancylivorus, and the grain or itch mite, Pyemotes ventricosus.

Organically Acceptable Method
Bloom time Bacillus thuringiensis sprays, sprays of the Entrust formulation of spinosad, and hand-applied mating disruption are organically acceptable methods for peach twig borer management.

Monitoring and Treatment Decisions

Monitor peach twig larvae during bloom and when shoots are emerging to determine that it is active. When emerging shoots are about 1 inch long, look for feeding at the base of flowers. Because damaged shoots do not wilt as they do in other stone fruit crops, detection can require a bit more care.

If larvae or their damage are observed at this time, two sprays of Bt or a single treatment of spinosad (Entrust, Success) or diflubenzuron (Dimilin) can be applied. Bt sprays at bloom can also be timed by dissecting hibernacula regularly from late February through bloom. Look at young trees or 1- to 4-year-old wood near branch crotches to detect the tiny hiberncula. The increase in the number of empty hibernacula reflects the number of larvae that have emerged and can be controlled by Bt once foliage is present.

Install pheromone traps in orchards by March 20 in the San Joaquin Valley and Central Coast and April 1 in the Sacramento Valley. If in-season sprays are necessary (as determined by damage in the previous generation), you will need results from trap catches and degree-day accumulations to time them. Once the first moth has been trapped, begin accumulating degree-days (DD) using a lower threshold of 50°F and an upper threshold of 88°F.

Research has shown that best control can be achieved when treatments are applied about 400 DD from the beginning of the flight if the fruit is still green; if fruit has begun to color, treat at 300 DD. If Bacillus thuringiensis is used, however, two sprays should be applied: one at 300-350 DD and the other at 450-500 DD.

Take weekly fruit samples after color break to detect any developing problems in the orchard and 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 formPDF).

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 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.
 
DELAYED DORMANT
 
A. NARROW RANGE OIL 4 0
  (Superior, Supreme) 4–6 gal 1–1.5 gal    
  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 . . .
  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.
  . . . 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 . . .
  LAMBDA-CYHALOTHRIN*
  (Warrior with Zeon) 2.56–5.12 fl oz 0.64–1.28 fl oz 24 14
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Do not exceed 0.2 lb a.i./acre/year.
  . . . or . . .
  ESFENVALERATE*
  (Asana XL) Label rates 12 14
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: An alternative to diazinon if resistance is suspected. Use when populations of peach twig borer are high. Use of this material during the dormant season may be detrimental to natural enemies of mites and result in mite outbreaks during the growing season.
 
MATING DISRUPTION
 
A. MATING DISRUPTANTS#
  (CheckMate PTB) Label rates 0 0
  COMMENTS: Used primarily in orchards where fruit is harvested before July and in organic orchards. (Only hand-applied mating disruptants are organically acceptable. Be sure to check with your certifier.) In later harvested orchards, mating disruption should be supplemented with a bloom treatment of Bt or spinosad. Place pheromone dispensers in orchards when you begin to catch the first moths in pheromone traps usually in April to May, depending on your location in the state. Apply in top one-third of canopy. Follow the manufacturer's recommendations for placement, the number of dispensers to use, and replacement intervals. Reapply the pheromones at the recommended timing for later varieties. If you are catching more than 5 moths per pheromone trap per week within one generation of harvest, however, treat with an insecticide rather than replacing dispensers. When using mating disruption, monitor the orchard regularly for damage at the end of each generation to verify that the technique is effective. Also monitor fruit from the tops of trees regularly for signs of larvae or damage; monitor more frequently during the final 4 weeks before harvest. Treat with insecticide if there are more than an average of 3 to 5 damaged terminals per tree after the first moth flight or if larvae are found in green fruit.
 
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. 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. 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.
 
B. 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 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.
 
C. SPINETORAM
  (Delegate WG) 3–7 oz 0.75–1.75 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.
 
D. CHLORANTRANILIPROLE
  (Altacor) 35WDG 3–4.5 oz 0.75–1.125 oz 4 10
  MODE OF ACTION GROUP NUMBER1: 28
  COMMENTS: Do not apply more than 9 oz/acre/year or make more than 4 applications a year. Do not apply with less than 100 or more than 200 gallons water/acre.
 
E. 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.
 
POSTBLOOM
 
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: Do not apply more than 29 fl oz/acre/year of Success or 9 oz/acre/year of Entrust. Most effective when applied at petal fall. This product is toxic to bees for 3 hours following treatment; apply in late evening after bees have stopped foraging.
 
B. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates 4 0
  MODE OF ACTION GROUP NUMBER1: 11.B2
  COMMENTS: Make two applications: one at 300-350 DD from biofix and the other at 450-500 DD. Good coverage is essential. Ground application using a concentrate rate (80–100 gal water maximum) is preferred. 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.
 
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) 70 WP 4.25 lb 1 lb 3 days 14
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Acidify water to 5.0 or below before adding phosmet.
 
E. LAMBDA-CYHALOTHRIN*
  (Warrior with Zeon) 2.56–5.12 fl oz 0.64–1.28 fl oz 24 14
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Do not exceed 0.2 lb a.i./acre/year.
 
F. ESFENVALERATE*
  (Asana XL) 4–6 oz 1.5–2 oz 12 14
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Use is not generally recommended on perennial crops in the San Joaquin Valley because high label rates can cause outbreaks of secondary pests. While low label rates reduce the potential for secondary outbreaks in the Sacramento Valley, they should only be used where resistance to organophosphates has not become a problem and other methods such as mating disruption are not feasible.
 
G. DIAZINON* 50WP 3 lb 1 lb 24 21
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Not allowable for use by many canneries. Avoid drift and tailwater runoff into surface waters. Where apricots are grown adjacent to waterways, do not use this material.
 
** 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/.

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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