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Obliquebanded Leafroller

Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae)

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INTRODUCTION

The obliquebanded leafroller (OBLR) is native to and widely distributed throughout temperate North America. Larvae feed on a wide range of plants; members of the rose family are their preferred hosts. OBLR outbreaks have resulted in severe damage to apple, peach, and pear fruit. The OBLR may have 1 to 2 generations a year, depending on the locality.

THE ADULTS

The spring flight of OBLR adults begins about 3 to 4 weeks after petal fall on apples, and continues for 3 to 4 weeks. In areas where the OBLR has 2 generations, a second flight occurs from early August through early September.

OBLR adults are 9 to 12 mm in length and have a wingspan of 20 to 27 mm. The forewings are reddish- brown and crossed by 3 oblique, chocolate-brown bands (Fig. 1). The hind wings, which are not visible when the moth is at rest, are pale yellow.

After emergence, females have a 24 hr preoviposition period. They then begin laying egg masses that gradually diminish in size with each succeeding egg mass laid. A female is capable of laying up to 900 eggs during her 7 to 8 day oviposition period.

THE EGGS

OBLR eggs are laid on the upper surface of leaves. They appear as greenish yellow masses (Fig. 2) measuring about 5 x 9 mm and may contain 200 or more eggs. The black head capsules of embryonic larvae become visible prior to hatching which usually occurs in 10 to 12 days.

THE LARVAE

OBLR larvae are indiscriminate feeders that pass through 6 instars. Newly hatched larvae have a yellowish green body and a black head and thoracic shield. Mature larvae (Fig. 3) are 20 to 25 mm in length and the head and thoracic shield may be either black or various shades of brown. The first summer brood of larvae emerge in early July and complete their development in late July or early August. Second brood larvae begin to emerge in mid-August, and feed until they reach the third instar in the fall, when they construct hibernation sites on twigs or bark and enter winter diapause. These overwintering larvae resume activity the following spring when the tree breaks dormancy and complete their development about 3 weeks after the apple blossom period.

Overwintered OBLR larvae (spring brood) first feed on water sprouts and then move throughout the tree. Those feeding on developing flower buds do so before bloom and continue to consume floral parts throughout the blossom period. After petal fall, these larvae continue feeding on the developing fruit. Newly hatched larvae of the first summer brood move to and feed on tender growing terminals, water sprouts, or developing fruit. As these larvae reach the third instar they display an increasing propensity to damage fruit. The second brood larvae, which develop in late summer and fall, feed primarily on leaves until they enter diapause, although they may occasionally damage fruit.

THE PUPAE

OBLR pupae are dark brown, about 11 mm in length, and are usually found in rolled leaves on the tree.

INJURY

The most serious injury from overwintering OBLR larvae occurs just prior to and shortly after petal fall, when the developing fruit is damaged. Many of these damaged fruits drop prematurely, but a small percentage remain on the tree, exhibiting deep corky scars and indentations at harvest (Fig. 4). Leaf injury by all broods is characterized by the larvae rolling leaves (Fig. 5) and feeding on surrounding foliage. The first summer brood larvae feed (Fig. 6) on the surface of developing fruit in late July and early August. This injury is similar to that caused by several other species of leafrollers. Fruit damage caused by first summer brood OBLR larvae is usually more serious than spring feeding by overwintered larvae because more of the fruit injured later in the season remains on the tree at harvest.

CONTROL

Several parasites attack OBLR larvae but do not adequately control the pest. Insecticides, effective against large larvae, must be applied at petal fall. If necessary, another spray should be applied in the summer, when most of the summer brood eggs have hatched.

An alternative strategy is to control overwintering larvae at petal fall as previously described, and apply sprays during June to kill the first summer brood adults and newly hatching larvae. Conventional organophosphate insecticides can be used in this program. The flight of adults can be monitored with pheromone traps. The first spray should be applied about 7 days after the first male moth is captured and subsequent sprays should be applied at 14-day intervals as long as the flight continues.

Consult the latest Cornell Cooperative Extension Recommendations for Commercial Tree-Fruit Production for the most current information on the use of pheromone traps for this insect and the relative effectiveness of insecticides against OBLR adults, newly hatched larvae, and large larvae.

GUIDE TO STAGES

Stage

Timing

Where to Look

Adults, (1st flight)

3 weeks after petal fall and continuing up to 4 weeks

Pheromone traps and resting on upper leaf surfaces.

(2nd flight)

Early August through early September

Same as above.

Eggs

Same as adult flight

Upper leaf surfaces

Larvae (overwintering)

Previous fall through 2 weeks past petal fall

Overwinters in protected sites throughout tree and in the spring moves to tender growth and flower buds.

1st generation

Early July through early August

Terminal growth and developing fruit.

2nd generation

Mid August through harvest

Primarily leaves and occasionally fruit.

Pupae

Three weeks past petal fall through early September

Tightly enclosed in or near feeding sites.

Authored by W. H. Reissig.

Published by the New York State Agricultural Experiment Station, Geneva, A Division of the New York State College of Agriculture and Life Sciences, A Statutory College of the State University, Cornell University, Ithaca. Funded in part by an Extension Service-USDA, IPM Grant.