Avocado leaf roller
|Description of adult|
Marked differences between the sexes occurs in the moth stage. The male is smaller (18 to 20 mm wingspan) than the female (25 to 30 mm wingspan). The forewings in the male are light brown with dark brown banding; in the female the forewings are dark tan to light brown with a darker oblique band and darker wing tip. The female has prominent wingtips and at rest the folded wings give the adult moths a bell shape.
The pale, flattened, yellow/orange eggs are laid in masses (sometimes exceeding 400) and overlap like fish scales. They are laid on the upper surface of mature leaves.
The young larvae drop on silken threads to be dispersed by the wind or they crawl a short distance to new shoots. They feed within shelters that they construct by rolling and webbing young foliage.
Little is known of the life history other than the eggs hatch after six to eight days, and that several generations occur each year.
Hosts include avocado, custard apple, carambola, coffee, tea and other horticultural crops but on these it is a relatively minor pest.
The caterpillars of this moth roll and web leaves together and also web leaves to berries. Inside these shelters the larvae live and feed on the leaf and berry tissue. Although severe leaf damage may be caused, the damage inflicted on the berries is more important. Large areas of the skin of berries may be eaten, sometimes to a depth of four millimetres. Damaged berries may be infected with anthracnose and drop or the injury may heal, forming scar tissue. Trees in flush are most susceptible since larvae prefer to feed on young growth and cause proportionately more damage on small, unexpanded leaves.
Several natural enemies have been recorded attacking leafrollers. These include a predatory of a syrphid fly larva, several wasp parasitoids, a tachinid fly parasitoid and egg parasitoids.
The extent to which these biocontrols operate depends on the level of disruption caused by pesticides applied to control other pests.
Sprays during flowering must be avoided to prevent death of bees and other pollinators.
Chemical registrations and permits
Check the Australian Pesticides & Veterinary Medicines Authority chemical database and permit database for chemicals registered or approved under permit to treat this pest on the target crop in your State/location. Always read the label. Always observe withholding periods.