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How to Manage Pests

UC Pest Management Guidelines

| More pests | More crops | About guidelines |

Speckled green fruitworm larva feeding on leaf.

Pear

Green Fruitworms

Scientific names: Speckled green fruitworm: Orthosia hibisci
Humped green fruitworm: Amphipyra pyramidoides

(Reviewed 2/07, updated 3/8)

In this Guideline:

DESCRIPTION OF THE PESTS

Immature larvae of both species are light green. Mature green fruitworms have green bodies and green heads. Speckled green fruitworms have cream-colored lines down the back and sides of the body. Humped green fruitworms are distinguished by a prominent hump on the last segment, bright yellow lines on the side, and less distinct white lines on the back. They have only one generation, which hatches from cluster to after petal fall.

DAMAGE

Young green fruitworm larvae feed on leaves, occasionally tying them together. Fruit feeding usually begins at petalfall when fruits are about 0.25 inch (6 mm) in diameter. At harvest, these fruit are misshapen and have large, roughened, russetted cavities.

MANAGEMENT

Green fruitworm populations in an orchard are usually spotty; often they occur near borders where windbreaks and other trees serve as sources of infestation. Generally this is a minor pest of pears that should be watched for when doing the cluster sample at bloom.

Organically Acceptable Methods
Sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are organically acceptable.

Monitoring and Treatment Decisions
Because populations of green fruitworm are often spotty within an orchard, look for its presence when taking the cluster sample at bloom. Examine 100 flower clusters from the tops and eye level of trees located throughout the orchard. If any green fruitworm larvae are found, a treatment may be necessary. For more information on monitoring pests at this time, 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.
 
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 when eggs are laid on residues) and as a larvicide. (larvae must ingest it for it to be effective). Treat at early egg hatch. 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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