How to Manage Pests
UC Pest Management Guidelines
Scientific name: Platynota stultana
(Reviewed 12/09, updated 5/10)
In this Guideline:
DESCRIPTION OF THE PEST
Omnivorous leafroller adults are small brown moths, about 0.4 inch (10 mm) long, with a snoutlike projection (palpae) that protrudes forward from the head. The portion of the wings nearest the body is a dark rusty brown color; the outer half is light tan. A small rusty brown spot occurs on the front edge of the wing. When at rest, the wings form a bell-shaped pattern. Females lay the small, elliptical eggs in clusters on the smooth surfaces of leaves and stems, overlapping them like fish scales. At hatching, larvae are about 0.06 inch (1.5 mm) long and white with light tan head capsules and thoracic shields. Middle instars are cream-colored and possess dark heads. Mature larvae are about 0.5 inch (12 mm) long and vary in color from cream to a dark brownish green depending on their diet. They have few setae (bristlelike hairs) scattered over the body and possess whitish oval spots along either side of a dark line running down the middle of the dorsum. The head capsule and thoracic shield of mature larvae is brown. When disturbed, larvae retreat into their nests or wiggle vigorously and drop to the ground on a silk thread.
This insect feeds on a wide variety of weeds and crops. The larvae build a nest by tying leaves together with silk webbing and remain inside this nest while feeding on the surface of the leaves. When leaves lie over a fruit, or if two fruit are touching, the larva will nest between the surfaces and feed on the fruit, causing substantial scarring. Larvae do not burrow into the fruit.
Regular field monitoring will help to detect potential problems with this pest. Weed control and site location play an important role in preventing infestations of omnivorous leafroller. Treatments may occasionally be necessary.
Early weed control in the area can help to reduce the population; however, the moths can fly for several miles. Avoid planting peppers near alfalfa or sugarbeet as these are good hosts.
Organically Acceptable Methods
Cultural controls and sprays of Bacillus thuringiensis or the Entrust formulation of spinosad are acceptable for used on organically certified produce.
Monitoring and Treatment Decisions
Inspect plants periodically during the growing season in several areas of the field for signs of leaves webbed together. Pay particular attention to weedy areas or locations near other susceptible crops. If nearby alfalfa or sugarbeet fields have been harvested, increase the intensity of the inspection. However, no treatment thresholds have been established.
Good coverage with the spray is critical for control because the larvae are difficult to reach within the folded leaves.
UC IPM Pest Management Guidelines:
Insects and Mites
E. T. Natwick, UC Cooperative Extension, Imperial County