Omnivorous Leafroller

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The larva of the omnivorous leafroller resembles other tortricid caterpillars, especially the orange tortrix, but it has white tubercles at the base of the bristles on its sides and back. Early instars (larval stage) have a black head and prothoracic shield; later instars have a light brown head and prothoracic shield. The larvae roll and tie leaves together or to fruit with silken threads. When mature they pupate inside the rolled leaves within a cocoon.

The adult moth has a 0.8 to 1 inch (2–2.5 cm) wingspan. The wings are fawn or rusty-brown, and possess a prominent light spot on the costal margins near the middle of the forewings, as well as other irregularly placed spots. The adult lives about ten days. Female moths lay overlapping eggs in clusters that resemble fish scales on the upper surface of leaves and on fruit. There are five to six generations a year, depending on temperatures.

Omnivorous leafroller is only rarely a pest of citrus in the San Joaquin Valley and in interior and intermediate districts of Southern California. In spring, small larvae spin webs and feed on new foliage. Later in the season they tie leaves to fruit and feed under the buttons, leaving ring scarring similar to that of citrus thrips. In summer and fall, they tie leaves to ripening fruit and feed on the rind.

Omnivorous leafroller is generally managed when monitoring for other pests from spring though fall indicates an insecticide application is necessary. Use selective (toxic to only a narrow group of insects) insecticides to preserve natural enemies.

Several parasites attack the larva of the omnivorous leafroller. The most common are a tachinid fly, Erynnia tortricis, and an eulophid wasp, Elachertus proteoteratis. Trichogramma spp. attack the eggs.

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

If it appears that omnivorous leafroller is present in the grove, monitor in the south and east quadrants of trees. In spring, look for small larvae under sepals when you monitor for citrus thrips. During summer, less frequent monitoring may be sufficient but check to see if parasites are effective. A higher number of larvae can be tolerated in spring, when they feed on young leaves, than in fall, when they are more likely to damage ripening fruit. Keeping this qualification in mind, a control action threshold of about 30 larvae per hour of search can be used.