Orange tortrix—Argyrotaenia franciscana =A. citrana
Orange tortrix (a tortricid, family Tortricidae) is a pest in Southern California and coastal areas. It feeds on many different plants including apple, avocado, caneberries, citrus, cole crops, coyote brush, geranium, grape, oak, pear, rose, stone fruits, strawberry, and willow.
Adults are about 1/2 inch long and bell shaped at rest as is characteristic of tortricid moths. Adults are variably colored moths with forewings that have blackish to dark markings. Overall the moths are mostly brown, gray, orangish, or silverish.
Eggs are oval, flattened, and cream colored. They overlap like fish scales as is typical of tortricids. Eggs are laid on smooth surfaces such as fruit and the upper surface of leaves.
Larvae have a greenish, orangish, or straw-colored body, a brown or straw-colored head, and brown prothoracic shield (plate on top of the first segment behind the head). They grow up to 3/5 inch long and resemble larvae of omnivorous leafroller. However, on omnivorous leafroller the small tubercles (mounds) at the base of the bristles on the side and back are chalky white. The tubercles on orange tortrix can match the color of the rest of the body and are brown, greenish, orange, or yellow but not white.
Pupae are oblong, orangish, and about 1/2 inch long. They are commonly found within webbed foliage.
Orange tortrix develops through 4 life stages: egg, larva, pupa, and adult. The adult female moth lays about 50 to 150 eggs during her several week life span. The hatching larvae develop through 5 increasingly larger instars. As with other tortricids, larvae produce silk strands with which they web together leaves, fruit, or both. They then feed within the webbed shelter. When disturbed larvae commonly wriggle and drop suspended on a silken thread.
Orange tortrix overwinters as larvae in protected places on the plant, including on alternative hosts such as weeds. It has two to four generations per year in coastal areas.
Orange tortrix chews and feeds on numerous plants, some of which are listed above. For a complete list of the plants on which it feeds, see HOSTS - a Database of the World's Lepidopteran Host Plants.
Early in the growing season, orange tortrix larvae primarily roll and chew young leaves. Once foliage hardens, later-generation larvae prefer to chew and feed on fruit, such as under the sepals of avocado and citrus. They can chew through the rind or skin of various fruits and cause holes where the surrounding flesh may become decayed. Damaged fruit may drop prematurely.
Many natural enemies feed on orange tortrix and can keep its abundance low when not disrupted by the application of persistent, broad-spectrum insecticides. A braconid wasp (Apanteles aristoteliae), two ichneumonid wasps (Exochus nigripalpis and another Exochus species), and two tachinid flies (Actia interrupta and Nemorilla pyste) are the most common parasites of orange tortrix. Female wasps lay their eggs in tortrix larvae (caterpillars), while tachinid flies lay eggs externally, usually on or near the caterpillar’s head. The parasite larvae feed inside and kill their host. Apanteles aristoteliae pupates in a white cocoon outside the killed caterpillar. Exochus pupates inside the dead caterpillar and leaves a round exit hole when the adult wasp emerges. Tachinids exit their dead host during its late larval or pupal stage, and each tachinid forms a dark reddish, oblong pupal case nearby. Predators of the caterpillars or moths include assassin bugs, larvae of brown lacewings, and spiders.
Control ants, reduce dust (e.g., periodically hose off small plants), and avoid the application of broad-spectrum insecticides for all pests on avocado and citrus trees to increase the effectiveness of natural enemies. See Protecting Natural Enemies and Pollinators for more tips on conserving natural enemies.
Remove weeds such as cheeseweed, filaree, and mustards that can host orange tortrix which move to infest nearby plants as adults. At the end of the growing season remove any old fruit and webbed debris on plants or the ground as these can allow this pest to overwinter.
Where fruit have previously been damaged by caterpillars, inspect hosts for orange tortrix larvae and other caterpillars at about 7- to 10-day intervals in spring. Look for caterpillars, chewing damage, webbed plant parts, and evidence of parasitism. If only a few caterpillars are found these can be crushed or the infested plant parts clipped off and disposed of in the trash. However if the caterpillars appear diseased or parasitized as describe above, leave them in place for the natural enemies to mature and attack additional caterpillars.
If caterpillars are abundant, Bacillus thuringiensis (Bt) or spinosad can be sprayed to thoroughly cover infested plant parts. Add horticultural oil to the spinosad to increase its efficacy persistence and also control moth eggs and certain other pests that are directly contacted by the spray. Avoid applying spinosad to plants in bloom because it is toxic to bees and certain natural enemies.
Adapted from Integrated Pest Management for Avocados and Integrated Pest Management for Citrus, University of California Statewide Integrated Pest Management Program (UC IPM).
Adults of orange tortrix.
Two orange tortrix larvae and their feeding damage to grapes.
Larva of orange tortrix.
Feeding damage of orange tortrix larvae on pears.