How to Manage Pests
UC Pest Management Guidelines
Scientific name: Archips argyrospila
(Reviewed 8/06, updated 3/09, pesticides updated 10/15, corrected 10/16)
In this Guideline:
DESCRIPTION OF THE PEST
Fruittree leafroller overwinters in the egg stage in irregular masses of 30 to 100 eggs cemented over with a secretion. Young larvae are light green caterpillars with black heads and are first seen at bud break. The mature larva is about an inch long and has a green body and black head. The black head helps distinguish fruittree leafroller from other leafrollers. There is one generation per season.
The fruittree leafroller feeds principally on leaves, but also feeds on blossoms, flower buds, and fruits during bloom. Tiny larvae work their way into opening leaf buds to feed. Once the tree has leafed out, larvae tie up leaves and live within leafrolls, feeding on leaves or fruit. Larvae damage fruit in much the same way as green fruitworms, resulting in shallow cavities in the fruit. Damaged fruits that remain on the tree develop deep bronze-colored scars with roughened, netlike surfaces.
Generally fruittree leafrollers are the first caterpillars seen in samples taken after green tip and have about 2 weeks to feed before the first codling moth spray goes on. Young larvae are easiest to control because they have not yet constructed a nest out of leaves, which protects them from insecticides.
Natural enemies specific for fruittree leafroller are not known, but a number of general predators, such as lacewing and lady beetle larvae, and parasites feed on fruittree leafroller larvae. Although these natural enemies help keep fruittree leafroller populations at low, nondamaging levels; occasional outbreaks still occur, especially in the San Joaquin and inner coastal valleys.
Organically Acceptable Methods
Applications of approved narrow range oil, Bacillus thuringiensis, and the Entrust formulation of spinosad are organically acceptable.
Monitoring and Treatment Decisions
Fruittree leafroller usually is effectively controlled by a dormant oil spray. Make an application thorough enough to cover egg masses. Check results by sampling for leafrollers at green tip. Examine 100 fruit clusters per block. If no worms are found, resample in 1 week. If more than one worm is found, treatment before pink bud may be necessary to prevent damage. Often infestations are usually confined to small, localized areas of the orchard and can be spot treated.
UC IPM Pest Management Guidelines:
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