How to Manage Pests

UC Pest Management Guidelines

Prune

Obliquebanded Leafroller

Scientific Name: Choristoneura rosaceana

(Reviewed 6/06, updated 4/09)

In this Guideline:


DESCRIPTION OF THE PEST

Obliquebanded leafroller larvae are yellowish green caterpillars. They are difficult to distinguish from fruittree leafrollers, which may also be present during bloom. When disturbed, they wiggle backwards and drop to the ground on a silken thread. Rolled leaves webbed together to form protective nests indicate the presence of leafroller larvae. Adult moths have dark brown bands running at oblique angles across their wings. Obliquebanded leafroller overwinters as larvae under bud scales of twigs; in the Central Valley there are two to three generations each year.

DAMAGE

Damage to prunes is primarily a concern for fresh market fruit growers. Larvae feed on prunes but generally do not cause serious economic damage unless brown rot invades the feeding wound.

MANAGEMENT

Dormant treatments and bloom time applications for other pests help keep leafroller populations under control. Leafroller damage is not a problem for prunes grown for the dried market but needs to be monitored on fresh market prunes from bloom to petal fall each season so that prompt action can be taken if damaging populations develop. Throughout the season, watch for the presence of leafrollers while monitoring for other pests. This is especially important in orchards where bloom time sprays and pheromone confusion are used to control peach twig borer and oriental fruit moth.

Biological Control

A number of parasites, including species of Macrocentrus, Cotesia (Apanteles), and Exochus, attack leafroller larvae. General predators such as lacewings, assassin bugs, and minute pirate bugs may feed on eggs and larvae. Preservation of natural enemy populations is an important part of keeping leafroller numbers low. Use selective materials that are least disruptive of biological control when treating other pests.

Organically Acceptable Methods

Organically acceptable management tools include biological control and sprays of oil, the Entrust formulation of spinosad, and Bacillus thuringiensis.

Monitoring and Treatment Decisions

Delayed dormant oil sprays generally help reduce populations as does a Bt program aimed at peach twig borer. When applying dormant oil or dormant oil plus an insecticide, wait until bud break in order to control larvae as they emerge from their overwintering site. You can also treat effectively during the green bud stage. To identify caterpillars present at bloom, view photos.

Postbloom treatments

Monitor obliquebanded leafroller postbloom by putting out pheromone traps and sampling developing fruit. Put out pheromone traps by April 15. (The lower load rate pheromone lures are the best indicators of population levels.) For more information see PHEROMONE TRAPS and record results on a monitoring form (PDF). Begin accumulating degree-days (DD) once moths have been caught in pheromone traps on two or more consecutive observation dates (the biofix). Use a lower threshold of 43°F and an upper threshold of 85°F (vertical cutoff). Begin sampling fruit at 930 DD from the biofix. Visually inspect 15 fruit from each of 80 trees per monitored orchard (a 1200 fruit sample) by walking around trees and looking for larvae or larval damage. Be sure to look for leaf rolls and on fruit where fruit-to-fruit contact occurs and where fruit are touching leaves. For each tree, record both the number of fruit with live larvae and fruit that have been damaged. Use a monitoring form (PDF) for this procedure.

Treat dried plums if over 2% (or more than 24 fruit) of the total fruit sampled have obliquebanded larvae and/or larval damage present. For fresh market prunes, treat if any larvae or damage is present.

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. 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 used alone will only provide partial control. 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.
 
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 . . .
  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) 4–6 oz 0.5 oz 12 14
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Pyrethroid residues remaining on leaves and bark will continue to affect mite predators long after application, increasing potential for spider mite infestations.
 
BLOOM
 
A. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates 4 0
  MODE OF ACTION GROUP NUMBER1: 11.B2
  COMMENTS: Make two 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. 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.
 
B. SPINOSAD
  (Entrust)# 1.71–2.5 oz 0.43–0.6 oz 12 7
  (Success) 6–8 oz 1.5–2 oz 12 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.
 
PETAL FALL and AFTER
 
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. 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. 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.
 
C. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates 4 0
  MODE OF ACTION GROUP NUMBER1: 11.B2
  COMMENTS: Timing is important because of short residual period; if larvae are small, Bt can effectively control them. Apply only during warm dry weather to control young actively feeding worms; may need to be applied more than once. Good coverage is essential.
 
** 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 the 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

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