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How to Manage Pests

UC Pest Management Guidelines

| More pests | More crops | About guidelines |

Fruittree leafroller larva.

Pear

Fruittree Leafroller

Scientific name: Archips argyrospila

(Reviewed 2/07, updated 3/8)

In this Guideline:

DESCRIPTION OF THE PEST

Fruittree leafroller overwinters in the egg stage in irregular masses of 30 to 100 eggs cemented over with a secretion. Young larvae are light green with black heads and are first seen at bud break. The mature larva is about an inch long and has a green body and black head. Moths fly during May or June, depending on the locale. The flight lasts about 3 weeks and females lay overwintering egg masses mainly on twigs in the upper parts of trees. There is one generation per year.

DAMAGE

The fruittree leafroller feeds principally on leaves, but also feeds on flower buds, blossoms, and fruits. Tiny larvae work their way into opening leaf buds to feed. Once the tree has leafed out, larvae tie up leaves and live within leafrolls, feeding on leaves or fruit. Larvae damage fruit in much the same way as green fruitworms, causing shallow cavities. Damaged fruits that remain on the tree develop deep bronze-colored scars with roughened, netlike surfaces.

MANAGEMENT

Fruittree leafroller is a minor pest in pears. Dormant oil treatments provide effective control. In-season treatments should be made only when monitoring indicates need.

Biological Control
Natural enemies specific for fruittree leafroller are not known, but a number of general predators, such as brown lacewings, green lacewings, and lady beetle larvae, and parasites feed on fruittree leafroller larvae. Although these natural enemies help keep fruittree leafroller populations at low, nondamaging levels; occasional outbreaks may occur, especially in the San Joaquin and inner coastal valleys.

Organically Acceptable Methods
Organically acceptable methods include applications of organically approved narrow range oil, Bacillus thuringiensis, and the Entrust formulation of spinosad.

Monitoring and Treatment Decisions
Fruittree leafroller usually is effectively controlled by a dormant oil spray. Make an application thorough enough to cover egg masses. Check results by sampling for leafrollers at green tip or early bloom. Generally fruittree leafrollers are the first caterpillars seen in samples taken after green tip. Examine 100 flower clusters collected randomly per block. If more than four fruittree leafrollers are found, treatment before the finger bud (swollen bud) stage may be necessary to prevent damage. Young larvae are easiest to control because they have not yet constructed a nest out of leaves, which protects them from insecticides. For more information on monitoring pests at bloom, see SAMPLING AT BLOOM.

Common name Amount to Use** R.E.I.+ P.H.I.+
(trade name) (conc.) (dilute) (hours) (days)
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.
 
DORMANT
A. NARROW RANGE OIL# 8 gal 2 gal 4 0
  . . . or . . .
  DORMANT FLOWABLE EMULSION 6–8 gal 2–3 gal 4 0
  . . . or . . .
  DORMANT PLUS 6–8 gal 3–4 gal 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Apply before February for best control. For narrow range oil, check with your certifier to determine which products are organically acceptable.
 
CLUSTER BUD to PETAL FALL
NOTE: Apply only if monitoring indicates a need.
A. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates — 4 0
  MODE OF ACTION GROUP NUMBER1: 11.B2
  COMMENTS: Least harmful to beneficials. Must be applied when worms are small. Apply starting at cluster bud to start of bloom. A second application may be required 7-10 days after the first. Occasionally a third treatment may be required. Most effective if applied when weather forecasts predict 3 to 4 days of warm, dry weather. Larvae are more active and feed more in warm weather than in cooler or rainy weather.
 
B. SPINOSAD
  (Entrust)# 2-3 oz 0.5-0.75 oz 4 7
  (Success) 6–10 fl oz 2–3.3 fl oz 4 7
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: To prevent the development of resistance to this product, rotate to a material with a different Group number after treating two consecutive generations. Do not apply more than 3 sprays/season directed at leafrollers. Do not apply more than 9 oz/acre/crop of Entrust or 29 fl oz of Success/acre/crop.
 
C. METHOXYFENOZIDE
  (Intrepid) 2F 16 fl oz — 4 14
  MODE OF ACTION GROUP NUMBER1: 18A
  COMMENTS: Functions both as an ovicide (when applied to eggs) and as a larvicide. (Larvae must ingest it for it to be effective). Make application at early egg hatch before webbing and sheltering begin. Spray coverage is extremely important. Ground application should use 200 gal water/acre with a sprayer speed of 1.5 mph. The addition of a spray adjuvant is recommended to enhance spray coverage.
 
**  Dilute rate is the rate per 100 gal water; use 400 gal solution/acre. Apply concentrate in 80-100 gal water/acre, or less 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 until the harvest may take place. In some cases the R.E.I. exceeds the P.H.I. The longer of these two intervals is the minimum time that must elapse before harvest may take place.
# Acceptable for 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/.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Pear
UC ANR Publication 3455
Insects and Mites
L. G. Varela, UC IPM Program, UC Cooperative Extension Sonoma Co.
R. B. Elkins, UC Cooperative Extension Lake Co.
R. A. Van Steenwyk, Insect Biology, UC Berkeley
C. Ingels, UC Cooperative Extension Sacramento Co.
Acknowledgment for contributions to the insects and mites section:
C. Pickel, UC IPM Program, UC Cooperative Extension Sutter/Yuba counties
P. W. Weddle, Weddle, Hansen & Associates
P. Chevalier, United Ag Products, Ukiah; B. Knispel, United Ag Products, Kelseyville
T. Lidyoff, Purity Products, Healdsburg; G. McCosker, AgroTech, Kelseyville
B. Oldham, Ag Unlimited, Ukiah
D. Smith, Western Farm Service, Walnut Grove
J. Sisevich, AgroTech, Kelseyville
B. Zoller, The Pear Doctor, Inc., Kelseyville

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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