Pest description and damage The oblique-banded leafroller larvae roll and tie leaves together for shelter and feeding. The newly hatched larva first mines the leaves, then rolls and ties leaves together. Often, they are first detected by the abundant holes in leaves. The larvae are green caterpillars with a light brown to black head. When disturbed, they thrash about violently, wriggle backwards and, and may drop from the leaf suspended by a silken thread. Their feeding on growing points on young plants can promote undesirable branching. Adults of the oblique-banded leafroller are bell-shaped, up to 1 inch long, tan to brown, with broad bands on the wings. Females lay overlapping masses of green eggs on the bark.
Biology and life history The oblique-banded leafroller overwinters as immature larvae under the bark on scaffold branches of a variety of host plants. Larvae may feed during warm periods in winter, but become active with warming spring weather and the onset of new growth. They feed for several weeks, and then pupate in rolled leaves. Adult moths emerge in late June or early July. These lay eggs for the second generation. The second generation hatches in early July and does the most damage.
Pest monitoring Start sampling for leafrollers in mid-April. Examine the terminal clusters for tightly rolled leaves and feeding damage on new growth. Watch for the first holes to appear and search nearby folded leaves for larvae, moth exit holes or evidence of larval silk that was used to hold the rolled leaf together.
Hand-pick rolled leaves containing larvae or pupae. Removal of overwintering sites, such as rolled leaves on the ground or plastered to plants, can reduce next year's population.
Very low temperatures in winter significantly reduce overwintering populations of larvae. Spiders and parasitic wasps, as well as predators like birds and the brown lacewing, greatly reduce leafroller populations throughout the year. There is a parasitoid wasp that specializes in leafrollers.
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For more information
LaGasa, E., T. Murray, and C. Looney. 2011. PNW Defoliators (http://www.invasives.wsu.edu/defoliators/species_faqs.html)