How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

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 brown 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.

DAMAGE

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. Spring feeding is on buds, and leaves. Larvae then enter the bunches 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.

MANAGEMENT

If orange tortrix is a problem, encourage biological control by the judicious use of insecticides, clean up the vineyard during the dormant period as described under cultural control and, if treatments are necessary, spot treat when possible, using thorough coverage of vines.

Biological Control
In coastal vineyards the dominant parasite of orange tortrix is Exochus nigripalpus subobscurus. The adult Exochus wasp is about 0.25 inch (6 mm) long, with a black head and body and yellow legs. This internal larval parasite emerges after the larva pupates and can be detected by the presence of round emergence holes. Moderate to heavy parasitism in late spring has resulted in season-long biological control in coastal vineyards. There are indications that coyote brush grown near vineyards in the Salinas Valley will increase parasitism by this parasite by allowing the parasite to overwinter on orange tortrix and other hosts found in the coyote brush. At least three other wasp species and one fly parasite are known to attack orange tortrix.

Spiders are often found in orange tortrix nests and undoubtedly feed on larvae.

Cultural Control
Clean up the vineyard during the dormant period. During winter, larvae are often found in weeds such as mallow (cheeseweed), curly dock, mustards, filaree, lupine, and California poppy. Vineyard cover crops of oats and barley are also attractive to this pest. Remove dried grape clusters on vines, and disc weeds and clusters on the ground. Do this work at least a month before shoots begin to develop in spring. Damage can often be prevented by harvesting as early as possible.

Organically Acceptable Methods
Cultural and biological controls and sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are organically acceptable management tools.

Monitoring and Treatment Decisions   Degree-day calculator    Degree-day table
Check vineyard areas that have a history of infestation or where infestation is suspected. See MONITORING CATERPILLARS section for monitoring procedures. Check varieties with compact clusters, developing shoots, flowers, or fruit clusters. Examine 10 flower clusters in the center of each of 20 vines for a total of 200 clusters. Look for rolled leaves that are glued to shoots. Also look for evidence of parasitism. Record results on a monitoring form (100KB, PDF). Later in the season, look for orange tortrix larvae and webbing in the bunches. If you find an average of 0.5-1 larva/vine, treatment may be warranted if parasites are not present. If the infestation is not widespread, spot treatments can be used. Inside coverage of bunches is essential; treat both sides of the row.

Pheromone traps. Pheromone traps for this pest are available and are useful in timing flights and subsequent treatments in coastal vineyards. Place pheromone traps in the vineyard in late December. Low-trap catches at the end of January to early February represent the beginning of adult emergence, which will give rise to the first generation. (Be sure to distinguish orange tortrix from garden tortrix, which may also be caught in traps but isn't a pest. View photos comparing them. Garden tortrix has a diagonal dark stripe that forms a chevron pattern when the wings are at rest and spot on each side of the forewing; both are lacking on orange tortrix moths). Use the low trap catches in late January through early February as the biofix (identifiable point in the life cycle) to start accumulating degree-days; low trap catches represent the beginning of adult emergence. Monitoring with pheromone traps after biofix will provide more information about subsequent generations of orange tortrix in the vineyard. For information on placing and monitoring pheromone traps, see PHEROMONE TRAPS.

Degree-days. Use degree-day accumulation, with a lower threshold of 43°F and an upper threshold of 78°F, from the date of lowest moth catch to predict the subsequent stages of the insect's life cycle. (For assistance in calculating degree-days, see "Degree-days".) Allowing 1,000+/-50 degree-days to accumulate after the date of lowest trap catch in late January/early February and in early June will indicate the timing of applications for control of the first and second generations.

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PUBLICATION

UC IPM Pest Management Guidelines: Grape
UC ANR Publication 3448
Insects and Mites
W. J. Bentley, UC IPM Program, Kearney Agricultural Research Center, Parlier
L. G. Varela, UC IPM Program, Sonoma County
F. G. Zalom, Entomology, UC Davis
R. J. Smith, UC Cooperative Extension, Sonoma County
A. H. Purcell, Environmental Science, Policy and Management, UC Berkeley
P. A. Phillips, UC IPM Program, Ventura County
D. R. Haviland, UC IPM Program, Kern County
K. M. Daane, Kearney Agricultural Research Center, Parlier
M. C. Battany, UC Cooperative Extension, San Luis Obispo County
Acknowledgment for contributions to the insects and mites section:
J. Granett, Entomology, UC Davis

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