Leafrollers

The garden tortrix, light brown apple moth, and orange tortrix are leafroller pests of cole crops in coastal areas.

Adults (moths) of these leafrollers have:

• light brown bodies with brown markings
• wings that form a bell shape while at rest
• protruding mouthparts that resemble a snout

Females lay masses of 20 to 170 eggs on smooth surfaces, such as shoots or the upper surface of leaves. The elliptical eggs are laid overlapping each other, resembling fish scales, and can be difficult to find. Eggs are often light green initially, then greenish-brown as the embryos develop.

When disturbed, leafroller caterpillars wriggle vigorously, drop from plants suspended by a silken thread, or both. Larvae and pupae overwinter in debris around the base of the plant.

Leafrollers are not well studied on cole crops. They may have one to four generations per year, depending on species and location.

Garden Tortrix

The adult garden tortrix has a dark brown marginal spot on each forewing. Anterior to the spot is a dark brown, diagonal stripe that forms a chevron (V shape) pattern when at rest and has a faint whitish line bordering the front edge. The darker markings and otherwise lighter color of the forewings distinguish adult garden tortrix from orange tortrix.

Garden tortrix larvae are slender, with light brown to green bodies. The light brown head has a small, distinct, dark brown spot on each side. There is a darker area (prothoracic shield) on top of the first segment behind the head.

Orange Tortrix

At rest, the orange tortrix female moth generally has a faint, brown, V-shaped mark where the forewings meet. The male has a darker, wider chevron mark. Compared to the dark brown chevron on garden tortrix, the V marking on orange tortrix is a lighter color and less distinct.

Larvae are 0.2 inch (5 mm) long just after hatching and grow to 0.5 inch, about twice the length of the mature garden tortrix. Older orange tortrix larvae have greenish to straw-colored bodies with a yellowish or straw-colored head and prothoracic shield. Larvae commonly feed singly on shoot tips and succulent leaves they web together with silk.

Larvae pupate in a silk cocoon in webbed foliage. Adults emerge about 1 to 3 weeks after pupation, depending on temperature. Orange tortrix has two to four generationsper year, and all stages can be present throughout the year.

Light Brown Apple Moth

(View the Field Identification Guide—PDF)

Light brown apple moth (LBAM) was previously classified as a federally quarantined invasive pest. However, the federal quarantine was lifted in December 2021, since the damage caused by this pest was less than expected.

The exotic light brown apple moth (LBAM) is found in coastal California from Los Angeles to Sonoma counties. In its native range (Australia), it does not survive well in hot, dry conditions. Because of its low tolerance to these conditions, it is less likely to be a problem in the San Joaquin Valley and southern desert, where these conditions occur seasonally.

Older larvae are pale to medium green with a light brown to yellowish head. The first segment behind the head (prothoracic shield) is greenish with no dark markings. However, the larvae cannot be reliably distinguished from other tortricids based on appearance.

Adults (moths) resemble many other tortricids, but light brown apple moth's wing coloration varies more greatly, ranging from mostly light brown to contrasting light and dark brown (two-toned), especially in males. Unlike garden tortrix and orange tortrix, male light brown apple moths have an extension on the outer edge of the forewing called a costal fold. Females lack the costal fold.

Moths emerge 1 to 3 weeks after pupation. They stay sheltered in foliage during the day, resting on the underside of leaves. Females begin to lay eggs at night on the upper side of leaves 2 to 3 days after emerging. Larvae overwinter as second to fourth instars on weeds or other vegetation and may survive during winter without feeding for up to 2 months. Depending on location, light brown apple moth may have two to four generations per year.

Leafroller feeding on marketed parts of cole crops or the florets is generally minor, so direct damage from leafrollers is rarely economically significant.

Leafroller larvae commonly tie one or more leaves together with silk and chew the foliage within these webbed shelters. Cole crops near native and riparian vegetation or urban landscapes may be more likely to attract leafrollers. Each leafroller species feeds on many species of plants, and adults can migrate from alternative hosts to lay their eggs on cole crops.

General insect predators and several species of spiders can reduce leafroller numbers by feeding on eggs or larvae. Larvae of several species of parasitic tachinid flies and wasps are especially effective natural enemies of leafroller larvae and pupae if broad-spectrum, persistent insecticides are not applied.

Early weed control and prompt destruction of infested crop residue can reduce leafroller numbers. However, moths can fly for several miles and cause new infestations.

Use biological and cultural control, as well as applications of Bacillus thuringiensis spp. kurstaki and the Entrust SC formulation of spinosad in an organically certified crop. When using B. thuringiensis, apply multiple times and at close intervals. When mixing, decrease the water volume to concentrate the dose ingested by the larvae, but make sure the volume applied still ensures thorough spray coverage. Targeting a specific larval stage is difficult because leafrollers have overlapping generations.

Use good sanitation to prevent infestations and monitor for leafrollers while monitoring for other caterpillars. Since the light brown apple moth quarantine has been lifted, insecticide applications for leafrollers in cole crops are rarely needed.

During the growing season through harvest:

1. Examine plants for frass (excrement consisting of black dots that look similar to poppy seeds), larvae, rolled leaves, and webbing, mainly under lower leaves and in the mid-canopy. Rolled leaves, one or more leaves webbed together, and webbing made by larvae are generally not difficult to locate.
2. Where leafroller activity is detected, search on nearby plants for more. Infestations are typically clustered.
3. When larvae are detected on leaves close to florets during harvest, separate those plants from the marketable produce and destroy them.

Insecticide sprays for other lepidopteran pests such as beet armyworm and diamondback moth may also control leafrollers.