Orange Tortrix

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The larva of the orange tortrix is a greenish to straw-colored caterpillar with a straw-colored head and prothoracic shield. The major distinguishing characteristic between orange tortrix and omnivorous leafroller caterpillars is that the small mounds at the base of the bristles on the side and back of the omnivorous leafroller are white, whereas on the orange tortrix they are not.

Orange tortrix larvae feed inside nests spun around plant parts. The larvae pupate in dense cocoons inside the nests and adult moths emerge in 8 days to 3 weeks, depending on temperature. Female moths lay 50 to 150 eggs on smooth surfaces such as stems, fruit, and the upper surface of leaves. In coastal areas, orange tortrix may have more than three generations a year, whereas in intermediate districts it has two or three. It is not a problem in the Central Valley.

Orange tortrix is primarily a pest on Valencias and navel oranges in Southern California. First generation orange tortrix larvae feed on leaves. Second generation larvae appear when the growth is hardening off and move preferentially to young fruit and feed around the button. This feeding causes only superficial scars. Later generations feed among clusters of ripening fruit, eating holes into the rind that allow decay organisms to enter; the fruit usually drops within 1 to 2 weeks.

Manage orange tortrix by monitoring throughout spring and summer and applying insecticides when necessary. Use selective (toxic to only a narrow group of insects) insecticides to preserve natural enemies.

Several parasites and predators attack orange tortrix. The most common parasites are two wasps, Apanteles aristoteliae and Exochus sp. These wasps lay their eggs in tortrix larvae and the parasites develop within. Apanteles pupates in a white cocoon outside the dead larvae, whereas Exochus pupates inside the larva and emerges through a round exit hole.

Use biological control and sprays of Bacillus thuringiensis in organically managed citrus orchards.

While orange tortrix larvae should be monitored throughout spring and summer, the period from May through July is especially important. At 7- to 10-day intervals, look for orange tortrix and evidence of parasitism mainly on the south and east quadrants of trees. If 15 larvae are found per hour of search on oranges and grapefruit, or 30 larvae per hour of search on lemons, an insecticide application may be warranted, depending on the level of parasitism.