How to Manage Pests

UC Pest Management Guidelines

Prune

Peach Twig Borer

Scientific name: Anarsia lineatella

(Reviewed 6/06, updated 4/09)

In this Guideline:


DESCRIPTION OF THE PEST

Small peach twig borer larvae are almost white with a distinct black head. As larvae mature they become chocolate brown with alternating dark and light bands around the abdomen. The light, intersegmental membranes contrasted with the brown body distinguish peach twig borer from other larvae found in stone fruits. Mature larvae are about 0.5 inch long.

Pupae are 0.25 to 0.4 inch long, brown in color and lack a cocoon. Pupation takes place in protected places on the tree and occasionally in the stem cavity of infested fruit, especially in nectarines and peaches.

Adult peach twig borer moths are 0.3 to 0.4 inch long with steel gray, mottled forewings. The long, narrow forewings are lightly fringed; the lighter gray hindwings are more heavily fringed. Prominent palpi on the head give the appearance of a snout. The bluntly oval eggs are yellow white to orange and are laid on twigs, leaves, or on the fruit surface.

Peach twig borer overwinters on the tree as a first- or second-instar larva within a tiny cell, called a hibernaculum, usually in crotches of 1- to 3-year-old wood, in pruning wounds, or in deep cracks in bark. The overwintering site is marked by a chimney of frass and is especially noticeable when first constructed or before winter rains set in. Larvae emerge in early spring, usually just before and during bloom, and migrate up twigs and branches where they attack newly emerged leaves and shoots. As shoots elongate, larvae mine the inside, causing the terminals to die back. Dead shoots are known as shoot strikes or flags.

Adults from the overwintered generation begin emerging in April or early May. First generation larvae develop in twigs during May and June and give rise to the next flight of moths in late June or early July. Larvae from this and subsequent generations may attack either twigs or fruit depending on fruit maturity and population density.

DAMAGE

Peach twig borer can damage stone fruits by feeding in shoots and causing shoot strikes, or by feeding directly on the fruit. Shoot damage is most severe on the vigorous growth of young (first to third leaves), developing trees because feeding kills the terminal growth and can result in undesirable lateral branching. As fruit matures, it becomes highly susceptible to attack; damage is most likely to occur from color break to harvest. Twig borer larvae generally enter fruit at the stem end or along the suture and feed just under the skin; the brown rot pathogen often invades this entry site. Peach twig borer damaged fruit usually drops before harvest and, therefore, may not be present at harvest.

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), methoxyfenozide (Intrepid), 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.

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 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 postbloom treatment in organic systems where other materials are not available. Mating disruption has not been reliable against peach twig borer when used alone. It is most effective in orchards with low moth populations that are not close to other untreated peach twig borer hosts or almond orchards. Efficacy is reduced by small orchard size, 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, and the grain or itch mite, Pyemotes ventricosus.

Organically Acceptable Method

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

Monitoring and Treatment Decisions
Bloom treatment timing

Monitor peach twig larvae during bloom and when shoots are emerging to determine that it is active. Look for the chewing damage they leave on buds. (To identify caterpillars present at bloom, view photos.) If larvae or their damage are observed at this time, two sprays of Bt or a single treatment of spinosad (Entrust, Success), methoxyfenozide (Intrepid), 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.

Fruit sampling to determine need to treat postbloom

In orchards where peach twig borer is not damaging every year and dormant or bloom treatments are not routinely scheduled, or if the crop will be marketed as fresh prunes, be sure to monitor for this pest. Place pheromone traps in the orchard March 20 in the San Joaquin Valley and April 1 in the Sacramento Valley. For more information, see PHEROMONE TRAPS and record results on a monitoring form (107 KB, PDF). Once the first moths are captured on two consecutive nights (the biofix), begin accumulating degree-days (DD) using a lower threshold of 50°F and an upper threshold of 88°F.

When 400 DD have accumulated from the biofix, begin monitoring fruit by walking around trees looking for the presence of peach twig borer larvae and damage (i.e., entries into the fruit). Be sure to look where fruit contact one another and where leaves touch fruit. Examine 15 fruit from each of 80 trees for a total of 1200 fruit. For each tree, record the number of fruit with larvae present and/or the number of damaged fruit on a monitoring form (PDF). For dried plums, treat if more than 2% (or 24) of the fruit are found with peach twig borer larvae or damage. For fresh market prunes, treat if any larvae or damage is evident.

Late-season fruit damage sample

In mid-July, take a fruit damage sample to assess the overall effectiveness of the current year's IPM program and to determine next year's needs. For more information, see FRUIT EVALUATION AT HARVEST. Record on a monitoring form (PDF) the number of fruit infested by larvae, type of larvae present, whether the damage is surface feeding only or if the larvae penetrated the fruit.

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, impact on natural enemies and honey bees, and impact of the timing on beneficials. 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. SPINOSAD
  (Entrust)# 1.25–2.5 oz 0.3–0.6 oz 4 7
  (Success) 4–8 oz 1–2 oz 4 7
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: Apply with a narrow range oil to suppress overwintering mite and scale populations. To avoid development of insect resistance, do not treat successive generations of the same pest with the same product.
 
B. DORMANT OIL such as:
  DORMANT FLOWABLE EMULSION 6 gal 1.5 gal 4 0
  NARROW RANGE OIL 4 gal 1 gal 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Oil applications at this time may cause some young shoots to burn or die back, especially in years when trees are water-stressed, or have recently been subjected to freezing temperatures or to dry winds. Dormant flowable emulsion is less likely to cause burn. The Moyer variety is highly susceptible to oil injury; delaying the oil spray until late Feb.to March 1 will reduce oil burn.
  . . . PLUS . . .
  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 . . .
  PHOSMET
  (Imidan) 70WP 4.25 lb 1 lb 3 days 7
  MODE OF ACTION GROUP NUMBER1: 1B
  . . . or . . .
  CHLORPYRIFOS*
  (Lorsban) 4EC 2 pt 0.5 pt 4 14
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Apply chlorpyrifos only during dormant or delayed dormant period and do not allow meat or dairy animals to graze in treated orchards. Levels in surface waters of this material that are high enough to be toxic to certain aquatic invertebrates have occurred following rains in January and February; avoid runoff into surface waters. Available for use under a special local needs registration.
  . . . 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.
  . . . or . . .
  METHIDATHION*
  (Supracide) 25W 6–8 lb 2–3 lb 48 0
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Apply before any blossoms open.
  . . . or . . .
  LAMBDA CYHALOTHRIN*
  (Warrior) 2.56–5.12 fl oz 0.64–1.28 fl oz 24 14
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Residues remaining on leaves and bark may continue to affect mite predators long after application, increasing potential for spider mite infestations.
 
BLOOM (preferred treatment timing)
 
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. SPINOSAD
  (Entrust)# 1.71–2.5 oz 0.43–0.6 oz 4 7
  (Success) 6–8 oz 1.5–2 oz 4 7
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: Do not apply more than 29 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.
 
C. METHOXYFENOZIDE
  (Intrepid) 2F 8–16 oz 2–4 oz 4 7
  MODE OF ACTION GROUP NUMBER1: 18A
  COMMENTS: Apply at petal fall. Use allowed under a supplemental label. Do not apply more than 16 fl oz/acre/application or 64 fl oz/acre/season.
 
D. 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 7
  (Success) 6–8 oz 1.5–2 oz 4 7
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: Do not apply more than 29 oz/acre/year of Success or 9 oz/acre/year of Entrust. 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. 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.
 
C. METHOXYFENOZIDE
  (Intrepid) 2F 8–16 oz 2–4 oz 4 7
  MODE OF ACTION GROUP NUMBER1: 18A
  COMMENTS: Use allowed under a supplemental label. Do not apply more than 16 fl oz/acre/application or 64 fl oz/acre/season.
 
D. PHOSMET
  (Imidan) 70 WP 4.25 lb 1 lb 3 days 7
  MODE OF ACTION GROUP NUMBER1: 1B
 
E. 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.
 
F. LAMBDA CYHALOTHRIN*
  (Warrior) 2.56–5.12 fl oz 0.64–1.28 fl oz 24 14
  MODE OF ACTION GROUP NUMBER1: 3
 
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.
 
H. MATING DISRUPTANTS#
  (CheckMate PTB) Label rates 4 0
  COMMENTS: Mating disruptants have not provided reliable control when used alone. Used primarily in organic orchards. 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 shoots strikes 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 shoot strikes per tree after the first moth flight or if larvae are found in green fruit.
 
** 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 the 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: 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 Insects and Mites:
  • W. O. Reil, UC Cooperative Extension Solano/Yolo counties

Top of page

PDF: To display a PDF document, you may need to use a PDF reader.


Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2014 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.

Agriculture and Natural Resources, University of California

Accessibility   /PMG/r606300211.html revised: April 25, 2014. Contact webmaster.