Orange Tortrix on Grape

Although orange tortrix is found in other areas it is generally considered a pest of grapes in the coastal areas and valleys where there is a marine influence for part of the day. At rest the orange tortrix adult is bell shaped and about 0.5 inch (12 mm) long. The female is orange-brown and generally has a faint V-shaped marking located midwing. The male is similar to the female except that it has darker markings. Eggs are laid in overlapping masses. The straw-colored caterpillars have a tan head and prothoracic shield. They are about 0.5 inch (12 mm) long when mature and very active. If disturbed, they wriggle sideways or backwards and either drop to the ground or hang by a silken thread. There are three overlapping generations per year and all developmental stages of this pest can be present throughout the growing season.

The garden tortrix, Ptycholoma peritana, frequently appears in orange tortrix traps and can be distinguished from orange tortrix by the dark brown diagonal stripe on the forewings that create a chevron pattern when the moth is at rest. The chevron pattern on the garden tortrix is darker than that of the orange tortrix. Garden tortrix also has a light-colored margin on the edge of the chevron, which orange tortrix lacks.

Orange tortrix causes the same kind of damage as the omnivorous leafroller in inland areas. Overwintering larvae feed on any soft, exposed vine tissue, weeds, and in grape mummies on the vine. Early spring feeding may occur on developing buds. During rapid shoot growth larvae feed within webbed leaves near the shoot tip. Larvae enter the clusters as early as bloom time and make nests of webbing among the berries. Besides injury to leaves and berry stems, their feeding on berries allows entry of bunch rot disease organisms.