Leafroller
Obliquebanded (Choristoneura rosaceana)
Orange Tortrix (Argyrotaenia citrana)
Insects and Invertebrates
OBLR Larva [ ]
Obliquebanded (Choristoneura rosaceana) Larva
Symptoms
Leafroller larvae are a major crop contaminant in the Pacific Northwest. As the larvae feed, they roll and tie together individual or clustered leaves at the shoot tip with webbing. The rolled leaves form a protective nest indicating the presence of leafroller larvae. Damage from webbing and feeding is rarely economic, but the larvae are a harvest contaminant especially in mechanically harvested fields.
OT Larva [ ]
Orange Tortrix (Argyrotaenia citrana) Larva
Identification
There are several species found in raspberry fields; however, the obliquebanded leafroller (OBLR) is the dominant species in British Columbia and Whatcom County and the orange tortrix (OT) is the dominant species found in the Willamette Valley of Oregon and Western Washington areas south of Whatcom County. OBLR can be found in southern growing regions, but is less of a problem due to the difference in timing of egg hatch. Larvae usually appear after the harvest of the primary varieties and are only a potential problem in late ripening caneberries.
Adult OBLR moths are bell-shaped and are slightly larger than the OT with a wingspan of ¾ to 1-inch. The tan forewings are crossed at oblique angles with two chocolate-brown bands. Mature larvae are about 1” long and are yellowish-green with dark brown or black heads. Young larvae are tan in color. Eggs are laid on leaves in a greenish patch of up to 200 eggs.
Adult OT moths are gray or fawn colored with darker mottling on the forewings and a wingspan of ¾ inch. Larvae are light brown to yellow green with a brown head. Larvae range from 1/8 to 1-inch when full grown. When disturbed, they wiggle backwards and drop to the ground on a silken thread. Eggs are cream colored, disc-shaped, and are laid overlapping in masses on the upper and lower surfaces of leaves.
OBLR Adult [ ]
Obliquebanded (Choristoneura rosaceana) Adult
Life History
Obliquebanded leafrollers overwinter as larvae hidden in debris, cracks, and other rough protective places. Larvae resume activity from overwintering in the spring. They spin themselves into tubes in the leaves. When disturbed, they will leave the leaf tube and lower themselves on strands of silk; they may be transported quite a long distance by wind on this silk. Pupation occurs within the leaf tube. Moths emerge from pupation in mid-June to mid-July. Eggs are laid after mating and hatch after 10-12 days. New larvae will move to new leaves by crawling or lowering themselves by silk. These larvae will pupate by August, and the next generation of adults is present in August and September. Second generation larvae will overwinter on the host plant or on other nearby plants. There are two generations per year.
Orange Tortrix overwinter as larvae in dead leaves webbed to canes or in other protective places. Larvae may feed during warm periods in winter, but become active in spring with the onset of new growth in late March and April. Pupation occurs in webbed leaves in the canopy and in leaf matter on the ground. Adult moths emerge in late April to May, which lay eggs for the next generation. Hatch of the first summer brood of larvae is likely to coincide with harvest and therefore contaminate fruit. OT has three to four overlapping generations per year. Larvae overwinter at different stages causing generations to overlap; eggs, larvae and adults may be found at any time during the summer.
OT Moth [ ]
Orange Tortrix (Argyrotaenia citrana) Adult
Monitoring
Pheromone lures are available for monitoring adult male flight for obliquebanded and orange tortrix. Place pheromone traps in the field early March for OT and by the end of April for OBLR. Change lure as suggested by the manufacturer (usually at one month intervals) and trap bottom when debris limits the usefulness of the trap. Check traps weekly. Count, remove, and record the number of adult moths found and divide by the number of days since last recording to determine trapped moths per day. This information can be used to determine peak flight, however this is more difficult to determine for orange tortrix due to its overlapping generations and successive egg hatches during harvest which can complicate control strategies.
Degree-days have been determined for OBLR life stages in Michigan. These can be sued to predict when to monitor for specific life stages when effective treatments should be made. Using a base of 43°F, life stage activity is:
| Number of Degree Days (base 43) |
Life Stage |
| 600 | First adult emergence |
| 800 | First eggs laid |
| 1,150 | Peak adult emergence |
| 1,250 | Peak egg laying |
| 2,050 | First emergence of second generation adults |
| 2,300 | First eggs laid by second generation adults |
To monitor for larvae, check 3-5 sites scattered throughout the field to determine the percentage of leafroller infested hills. Each site should represent a different acre of the field; such as a corner acre, middle acre, or an edge acre. At each site, select 20 hills and examine shoot tips for presence of caterpillars. Examine a maximum of 5 shoot tips/hill to determine if the hill is infested. Once an infested shoot tip is found, do not examine any more shoot tips at that hill, and record the hill as infested. If you examine five shoot tips without finding any caterpillars, record the hill as clean. Record the number of infested hills for each site that you sample. Add up the total number of infested hills that were detected and divide by the total number of hills that you examined. Multiply this number by 100 and you have the percentage of leafroller-infested hills. Sample for larvae at least every two weeks and change scouting location each visit in order to cover all areas of the field. Scouting for larvae should continue through the end of the harvest season.
A beating tray can also be used to monitor for OT larvae, although action levels based on this monitoring tool have not been established. Conduct 10 beating tray evaluations in 4-5 sites per field by placing tray under plant canopy and knocking the wire above a few times. Identify and record the number of OT larvae and make note of any other potential harvest contaminants.
Thresholds and Management
Threshold varies according to end product and processor. Processors of IQF fruit have a zero tolerance for leafroller larvae. Check with you buyer for their threshold. However, a good starting threshold is 10% or more larvae infested hills, based on examination of a minimum of 20 hills per acre. Effective treatment relies heavily on timing applications to newly hatched, small larvae and good coverage. Repeat applications may be needed, although overuse of broad-spectrum insecticides can intensify problem by eliminating natural control agents. If larvae levels are low, biological materials such as Bt (Bacillus thuringiensis) formulations may be effective.
Proper sanitation practices during the dormant season will also help prevent a buildup of leafrollers. Mot overwintering larvae survive in plant debris on the ground, in surrounding weeds, or in debris pinned between canes. Destroy weeds, move trash into the middle of the row for cultivation and wait until leaves fall before training canes.
Action thresholds for adult flight activity and using the beating tray have not been established.
Resources
University of California, UC IPM Online, Caneberries: Leafrollers
http://www.ipm.ucdavis.edu/PMG/r71300211.html
Pacific Northwest Insect Management Handbook, Cane Fruit Pests
http://uspest.org/pnw/insects
Oregon State University: Integrated Plant Protection Center, Orange Tortrix
http://uspest.org/pdf/reb77.pdf
Michigan State University Extension, Fruit IPM Factsheet, Obliquebanded Leafroller
http://web1.msue.msu.edu/vanburen/oblr.htm