How to Manage Pests
UC Pest Management Guidelines
Orange tortrix (family Tortricidae) is an uncommon problem on avocados grown in coastal areas. It rarely is injurious at inland growing areas. Orange tortrix feeds on various weeds and crops including citrus, grape, and strawberry.
Orange tortrix and amorbia adults resemble each other. They are orangish to tan moths with dark shading across their folded wings. At rest, their folded wings flare out at the tip so their overall shape resembles a bell. Orange tortrix adults are about 0.4 inch long, about one half the size of amorbia adults.
Orange tortrix and amorbia females lay eggs overlapping in a mass. Orange tortrix oviposits on the surface of young leaves, green twigs, or green fruit. Each egg is pale green, flat, oval, and has a finely reticulated surface. Females lay several clusters that range from a few eggs to over 150 eggs per mass. Eggs hatch in about 9 days.
Larvae usually feed singly on shoot tips or on succulent leaves in nests they web together with silk. Larvae develop through 5 to 7 instars over about 40 days. They are about 0.08 inch (2 mm) long at hatching and about 0.5 inch long when mature. Larvae have a brownish or straw-colored head and prothoracic plate (the top of first segment behind the head). The variable body color is dark gray, greenish, straw-colored, or tan. Orange tortrix and amorbia larvae typically wriggle vigorously backwards or sideways when disturbed. Orange tortrix may drop to the ground or remain suspended from the leaf on a silken thread.
Larvae form a dense silken cocoon where they pupate within webbed foliage. Adults emerge in about 1 to 3 weeks, depending on temperature. Orange tortrix has two to four generations per year, with all stages present throughout the year.
Most larval chewing occurs within silken webs on outer-canopy shoots. During bloom, tiny larvae sometimes feed among flowers. Larvae also feed on green bark, girdling some twigs. White exudate may cover wounds on larger twigs. Least common is fruit feeding, but this is the economic damage. Fruit injury closely resembles damage from other avocado caterpillars, except that orange tortrix tends to chew deeper holes. Feeding near the stem end of fruit and on the stem may cause fruit to drop.
Conserve natural enemies, which usually keep caterpillars below damaging levels. Modify cultural practices to reduce pest reproduction and survival. Avoid applying broad-spectrum or persistent insecticides for any pests. Caterpillar outbreaks commonly occur after spraying carbamate or organophosphate insecticides, which poison parasites and predators. When pesticides are warranted, limit application to the most infested spots to provide refuges from which natural enemies can recolonize after treatment.
Organically Acceptable Methods
and Treatment Decisions
There are no established thresholds, and treatment for orange tortrix is rarely warranted. If sprays are needed, use Bacillus thuringiensis when larvae are small. Spraying with malathion often leads to outbreaks of other pests and is not recommended.
UC IPM Pest Management Guidelines: Avocado