How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PESTS

Four leafrollers in the family Tortricidae, apple pandemis, light brown apple moth, omnivorous leafroller, and orange tortrix, are pests of caneberries. Apple pandemis, light brown apple moth, and orange tortrix occur primarily in coastal areas where they are pests on both blackberries and raspberries while omnivorous leafroller is a pest of these crops primarily in the Central Valley.

Leafroller moths lay elliptical, green eggs on smooth surfaces, such as upper leaf surfaces, berries, or smooth shoots. Eggs are laid in clusters with individual eggs overlapping each other like fish scales. As embryos within eggs develop, eggs turn from green to greenish brown. Newly hatched larvae are less than 0.6 inch (1.5 mm) long, and mature larvae are about 0.75 inch (18 mm) long.

Apple pandemis larvae are green with yellowish green or straw-colored head capsules. Light brown apple moth larvae are nearly indistinguishable from other leafroller larvae; take suspect larvae to the local agricultural commissioner for proper identification. Orange tortrix larvae have straw-colored to greenish bodies with a yellowish head capsule and prothoraic shield. Omnivorous leafrollers resemble orange tortrix but have small, white tubercles from which bristles arise along the back and sides of their body. When disturbed, leafroller larvae wriggle vigorously and drop on a fine silk thread. Pupae are creamy-white at first, then turn dark brown.

Adult moths are about 0.5 inch (12 mm) long. When at rest leafroller moths position their wings in a bell shape. Orange tortrix moths have light brown forewings. The forewings of omnivorous leafroller moths are dark, rusty brown on the upper half, tan on the lower half; a darker colored band extends outward on the resting moth from the middle of the wings in a V-shaped pattern that separates dark and light areas. The wings of apple pandemis are also banded in color but the center band on the forewings is edged with white. While the adult coloration of light brown apple moth is variable, males may be distinguished from other leafrollers by an extension of the outer wing. Leafroller moths have protruding mouthparts that resemble a snout.

Apple pandemis and orange tortrix both have two to three generations a year, whereas the omnivorous leafroller has four to five. It is not yet clear how many generations a year the light brown apple moth has in California.

DAMAGE

Leafroller larvae feed on fruit and foliage. Foliar injury is generally minor; the primary problem caused by leafrollers is that they get into and contaminate fruit. Damage from light brown apple moth is similar to that of other leafrollers but as an "A" rated pest, it should not be present in strawberry plantations.

MANAGEMENT

Biological control and good sanitation are important factors in reducing leafroller populations. Spray treatments are recommended if the field has a history of leafroller problems or if serious infestation occurred the previous season. Otherwise, use chemical treatments only when determined necessary by careful monitoring.

Biological Control
Several wasps have been recorded as parasites of omnivorous leafroller including Goniozus platynotae, Trichogramma sp., Cotesia (Apanteles) sp., Microgaster phthorimaeae, Macrocentrus ancylivorus, Cremastus platynotae, Diadegma compressus, Elachertus proteoteratis, and Spilochalcis sp. Two flies, Erynnia tortricis and Nemorilla pyste, are also known as omnivorous leafroller parasites. All are larval parasites, except the Trichogramma sp., which is an egg parasite.

Several parasites also attack orange tortrix. The most common two are Apanteles aristolilae and Exochus sp. An external parasite, Hormius basalis, also occurs. Major parasites of apple pandemis include the parasite wasp, Horogenes sp., and a tachinid fly, Nemorilla floralis.

Also, general insect predators and several species of spiders may influence the leafroller populations by feeding on eggs or larvae. Some insect predators are green lacewing (Chrysoperla carnea), minute pirate bug (Orius tristicolor), and damsel bug (Nabis sp.). Spiders in the family Theridiidae are common predators.

Cultural Control
Proper sanitation practices during the dormant season help prevent a buildup of leafrollers. Most overwintering larvae survive in surrounding weeds or in trash beneath the canes. Destroy weeds and move trash to the middle of rows where it will be disked into the soil.

Organically Acceptable Methods
Cultural and biological controls and sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are acceptable for use on organically certified crops.

Monitoring and Treatment Decisions
Begin monitoring for the leafrollers in early spring by examining plants for larvae. Larvae may web leaf surfaces together, especially those of newly extending laterals, and live between them. Or they may roll leaves and live in the folds. One way to evaluate infestation level in early spring is to carefully inspect newly extending laterals for webbing, frass, leaf damage, and the presence of larvae. Another good way to look for leafrollers is to agitate the hedgerow, either by beating or shaking the plants, and collect the fallen material into a bucket or wide, flat container. Carefully sift through this material to detect larvae (early larval instars can be quite small). Concentrate monitoring activities in suspected or previously infested areas.

Pheromone traps placed in caneberry plantations can be good indicators of moth flight activity and may help to pinpoint when the most intensive monitoring for larvae should be done. Concentrate examinations of the plants in those periods after flight peaks when larvae are increasing in number.

It is especially important to thoroughly inspect plants 7-10 days before the beginning of harvest to determine the need for treatment. Large numbers of larvae detected at this time increase the chance of having larvae in harvested fruit, and these odds should be reduced.

PUBLICATION

UC IPM Pest Management Guidelines: Caneberries
UC ANR Publication 3437
Insects and Mites
E. J. Perry, UC Cooperative Extension, Stanislaus County
M. P. Bolda, UC Cooperative Extension, Santa Cruz County
L. J. Bettiga, UC Cooperative Extension, Monterey County
Acknowledgment for contributions to the insect and mite section:
R. M. Tyler, UC Cooperative Extension, Santa Cruz County
E. Show, Driscoll Strawberry Associates Inc., Watsonville, CA

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