How to Manage Pests

UC Pest Management Guidelines

Pistachio

Obliquebanded Leafroller

Scientific name: Choristoneura rosaceana

(Reviewed 2/07, updated 2/09)

In this Guideline:


DESCRIPTION OF THE PEST

Larvae of the obliquebanded leafroller are yellowish green caterpillars. 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 second-instar larvae under bark and in crevices of trees. There are three generations each year in the pistachio-growing areas of the state.

DAMAGE

Obliquebanded leafroller larvae cause two types of damage to pistachios. When populations are high, leaves are tied together, which kills portions of leaves and reduces the overall photosynthetic capacity of the trees. The most important damage to the crop, however, is when larvae invade the clusters from June to August and feed on the peduncles (stems). This causes the peduncles to dry and shrivel, thus reducing crop yield.

MANAGEMENT

Spring treatments of young caterpillars with Bacillus thuringiensis or spinosad and monitoring with pheromone traps to time summer applications are the key approaches to monitoring this pest in pistachio.

Biological Control

There are several parasite species (Macrocentrus iridescens, Bracon sp. and Goniozus sp.) that attack obliquebanded leafroller and can significantly reduce its populations in the second and third generations. None of these parasitoids are commercially available (the Goniozus species that attacks obliquebanded leafroller is not G. legnei).

Organically Acceptable Methods

Springtime sprays of Bacillus thuringiensis and summer spray of the Entrust formulation of spinosad are acceptable for use in an organically managed orchard.

Monitoring and Treatment Decisions

To time summer treatments, put out pheromone traps by mid-April (Kern and King counties) and April 25 from Fresno north. In addition, look for obliquebanded leafroller larvae when traps indicate adults have emerged. Examine trees for leaf rolls, leaves tied together, and live larvae. When male moths are first found in traps, begin degree-day calculations (upper threshold 94°F, lower threshold 43°F). Treat when 800 degree-days have accumulated.

Common name Amount/Acre** R.E.I.+ P.H.I.+
(trade name)   (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 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.
 
SPRING
 
A. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates 4 0
  MODE OF ACTION GROUP NUMBER1: 11.B1
  COMMENTS: Apply when trees are beginning to leaf out and small larvae first emerge from bark scales. Bt is a stomach poison and must be consumed by the caterpillar; therefore, it is most effective when applied during warm, dry weather when larvae are actively feeding. Most effective when larvae are young. May require more than 1 treatment; apply second application 7–10 days after the first. Can be used during bloom.
 
SUMMER
 
A. SPINOSAD
  (Entrust)# 1.25–3 oz 4 14
  (Success) 4–6 oz 4 14
  MODE OF ACTION GROUP NUMBER1: 5
 
B. METHOXYFENOZIDE
  (Intrepid) 2F 8–16 fl oz 4 14
  MODE OF ACTION GROUP NUMBER1: 18A
  COMMENTS: Do not apply more than 64 fl oz/acre/season.
 
C. PHOSMET
  (Imidan) 70W 4–5 lb 72 14
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Do not apply more than 5.66 lb/acre/season as a foliar spray. Do not apply after hull split reaches 10%.
 
** Unless otherwise noted, apply with enough water to ensure adequate coverage.
+ 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.
# Acceptable for 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 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/.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Pistachio
UC ANR Publication 3461

Insects and Mites

  • W. J. Bentley, Kearney Agricultural Center, Parlier
  • R. H. Beede, UC Cooperative Extension, Kings County
  • K. M. Daane, Biological Control, UC Berkeley/Kearney Agricultural Center, Parlier
  • D. R. Haviland, UC Cooperative Extension, Kern County
Acknowledgment for contributions to Insects and Mites:
  • R. E. Rice, Kearney Agricultural Center, Parlier

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