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How to Manage Pests

UC Pest Management Guidelines

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Pear

Obliquebanded Leafroller

Scientific name: Choristoneura rosaceana

(Reviewed 2/07, updated 3/8)

In this Guideline:

Description of the pest
Damage
Management

Important links
Publication
Glossary

DESCRIPTION OF THE PEST

Obliquebanded leafroller overwinters as immature larvae under bud scales. Larvae are yellowish green with brown to black heads. As they mature, larvae construct tubular shelters from a single leaf. Moths of obliquebanded leafrollers have alternating light and dark brown bands across their forewings. They begin emerging in mid-May in warmer districts to early June in cooler areas. There are usually two generations a year. The larvae of the summer generation are found feeding between the fruit in a cluster.

DAMAGE

Damage occurs when larvae attack fruit. Larvae feed on flower parts and fruit early in the season. When they feed on young fruit, they cause deep depressions that become rough and russetted by harvest. The summer generation causes extensive superficial skin tunnels (giving rise to the name "skin worms") when insects feed between two pears in a cluster.

MANAGEMENT

Obliquebanded leafroller is an occasional pest that can become more damaging in orchards where mating disruption is used to control codling moth. It can occur in orchards in spring and summer. Summer damage is most commonly seen in orchards where a switch has been made to highly selective codling moth materials, including mating disruption, that do not control obliquebanded leafrollers. Treat only if monitoring indicates need.

Biological Control
The parasitic wasp Macrocentrus iridescens has been observed attacking obliquebanded leafroller larvae in the Central valley and in Central Coast and North Coast apple orchards.

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

Monitoring and Treatment Decisions
Bloom. Check the orchard at cluster bud for the presence of larvae and feeding damage on flowers. From 50 trees, collect one fruit spur from the top and one at eye level, for a total of 100 spurs.

If more than one larva is found, treat immediately. A number of insecticides that don't create problems with water-quality issues are effective in controlling this pest, including Bacillus thuringiensis, spinosad (Entrust, Success), and methoxyfenozide (Intrepid). The best timing for control of overwintering larvae is at full bloom or early petal fall.
If only one larva was found at cluster bud, use pheromone traps to monitor the first summer flight (see PHEROMONE TRAPS). Place pheromone traps in the orchard in mid-April. Begin accumulating degree-days as soon as traps begin to catch moths (this is the biofix) using a lower threshold of 43°F and an upper threshold of 85°F. (For assistance in calculating degree-days, check "Degree-days ").

For more information about monitoring at this time, see SAMPLING AT BLOOM.

Fruit development. To determine if a treatment is needed for the summer generation, monitor fruit where it touches other fruit in 20 trees in a block. Collect one fruit cluster from the treetop and one from eye level for a total of 40 clusters. If more than two clusters contain leafrollers, treat at about 600-700 DD from the biofix (i.e. from moth catch). For information on monitoring other pests at this time, see SAMPLING DURING FRUIT DEVELOPMENT.

Harvest fruit sample. At harvest, assess your IPM program by monitoring fruit in the bins for obliquebanded leafroller damage. Sample 200 fruit from 5 bins per orchard (or 20-acre block in large orchards) for a total of 1,000 fruit. For more information about monitoring at this time, see HARVEST FRUIT SAMPLE.

Summary of Important Links

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.

DELAYED DORMANT TO GREEN TIP

CHLORPYRIFOS*

(Lorsban) 4E

4 pt

1 pt

4 days

N.A.

MODE OF ACTION GROUP NUMBER¹: 1B

COMMENTS: For use during dormant/delayed dormant season only. For best results, delay the delayed dormant treatment as long as possible. Chlorpyrifos has been found in surface waters at levels that violate federal and state water quality standards. Provide 100-ft buffer zone from any sensitive aquatic site. Make application when the wind speed is between 3 and 10 miles per hour. Avoid drift and tail water runoff into surface waters.

ESFENVALERATE*

(Asana)

Label rates

MODE OF ACTION GROUP NUMBER¹: 3

COMMENTS: Apply before bloom at green tip to kill overwintering larvae. Provide 100-ft buffer zone from any sensitive aquatic site. Make application when the wind speed is between 3 and 10 miles per hour.

CLUSTER BUD TO PETAL FALL

BACILLUS THURINGIENSIS ssp. KURSTAKI#

(various products)

Label rates

—

MODE OF ACTION GROUP NUMBER¹: 11.B2

COMMENTS: Least harmful to beneficials. Bt is a stomach poison and must be consumed by the leafroller; therefore it is most effective when applied during warm, dry weather when larvae are actively feeding. Most effective against young larvae. Apply starting at cluster bud. Requires more than 1 treatment; apply second application 7–10 days after the first. Most effective if applied when weather forecasts predict 3 to 4 days of warm, dry weather.

SPINOSAD

(Entrust)#

2-3 oz

0.5-0.75 oz

(Success)

6–10 fl oz

2–3.3 fl oz

MODE OF ACTION GROUP NUMBER¹: 5

COMMENTS: Apply with oil. Most effective when applied at petalfall. 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.

METHOXYFENOZIDE

(Intrepid) 2F

16 fl oz

—

MODE OF ACTION GROUP NUMBER¹: 18A

COMMENTS: Functions both as an ovicide and as a larvicide. (Larvae must ingest it for it to be effective). Treat overwintered larvae at petal fall 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.

SUMMER

BACILLUS THURINGIENSIS ssp. KURSTAKI#

(various products)

Label rates

MODE OF ACTION GROUP NUMBER¹: 11.B2

COMMENTS: Least harmful to beneficials. Bt is a stomach poison and must be consumed by the leafroller; therefore it is most effective when applied during warm, dry weather when larvae are actively feeding. Most effective against young larvae. For summer generation, begin applications at 600 to 700 DD from biofix. Requires more than 1 treatment; apply second application 7–10 days after the first. 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.

METHOXYFENOZIDE

(Intrepid) 2F

16 fl oz

—

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). For summer generation, begin applications at 600 to 700 DD from biofix. If monitoring indicated a need, make a second application in 10–14 days. 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.

SPiNOSAD

(Entrust)#

2-3 oz

0.5-0.75 oz

(Success)

6–10 fl oz

2–3.3 fl oz

MODE OF ACTION GROUP NUMBER¹: 5

COMMENTS: For the summer generation, apply at 600 to 700 DD from biofix. 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.

**	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.
*	Permit required from county agricultural commissioner for purchase or use.
#	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/.

IMPORTANT LINKS

Degree-day calculator

PUBLICATION

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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