How to Manage Pests
UC Pest Management Guidelines
Scientific name: Argyrotaenia franciscana (formerly A. citrana)
(Reviewed 8/06, updated 3/09, pesticides updated 10/15)
In this Guideline:
DESCRIPTION OF THE PEST
Orange tortrix, also called apple skinworm, is a pest in California coastal areas. The moths are 0.5 inch long with tan to rusty brown forewings. The fully grown larvae are about 0.5 inch long, straw colored to green, with light brown heads. They are active and quickly wiggle backwards when disturbed, dropping to the ground or spinning down a silken thread.
Orange tortrix is an occasional pest in apple orchards. The principal damage caused by orange tortrix larvae is feeding on the surface of fruit, where they leave shallow, irregular scars. Generally they feed within a fruit cluster; occasionally they tie a leaf to the fruit's surface and feed under it.
Orange tortrix is frequently controlled by parasites, especially in warm years when high temperatures slow its development. In cool years, higher populations occur, and natural enemies may not be able to hold populations below economically damaging levels; additional control measures may be needed.
Several parasites and predators attack orange tortrix. Two parasitic wasps, Apanteles aristolilae and Exochus sp., are the most common. Hormius basalis, an external parasite, also occurs. Brown lacewing, Hemerobius pacificus, is a general feeder on orange tortrix.
Thin fruit to one or two fruit per cluster to reduce available habitat and to increase exposure of larvae to parasites, predators, and insecticides. Remove and dispose of mummy fruit to reduce overwintering orange tortrix. Orange tortrix feeds on many weeds found in orchards, such as mustard. Plant low-growing grass cover crops to reduce overwintering hosts of orange tortrix.
Organically Acceptable Methods
While rarely a significant pest in organic orchards, biological and cultural controls and sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are organically acceptable methods for pest control.
Monitoring and Treatment Decisions
Usually orange tortrix does not appear in apple trees until June when eggs from the first summer generation are laid. Sample trees for larvae once a month in June, July, and August; take the first sample no later than mid-June. Examine 10 trees of each variety in each block for 4 minutes each. Each larva found, whether orange tortrix, apple pandemis, or eyespotted bud moth. Correlates to about 1% fruit damage at harvest.
UC IPM Pest Management Guidelines: Apple
Insects and Mites
L. R. Wunderlich, UC Cooperative Extension, El Dorado County
Acknowledgment for contributions to Insects and Mites:H. L. Andris, UC Cooperative Extension, Fresno County
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
W. W. Coates, UC Cooperative Extension, San Benito County
C. Pickel, UC IPM Program, Sutter/Yuba counties