How to Manage Pests
UC Pest Management Guidelines
Scientific name: Choristoneura rosaceana
(Reviewed 2/07, updated 2/09)
In this Guideline:
DESCRIPTION OF THE PEST
Larvae of the obliquebanded leafroller are yellowish green caterpillars. When disturbed, they wiggle backwards and drop to the ground on a silken thread. Rolled leaves webbed together to form protective nests indicate the presence of leafroller larvae. Adult moths have dark brown bands running at oblique angles across their wings. Obliquebanded leafroller overwinters as second-instar larvae under bark and in crevices of trees. There are three generations each year in the pistachio-growing areas of the state.
Obliquebanded leafroller larvae cause two types of damage to pistachios. When populations are high, leaves are tied together, which kills portions of leaves and reduces the overall photosynthetic capacity of the trees. The most important damage to the crop, however, is when larvae invade the clusters from June to August and feed on the peduncles (stems). This causes the peduncles to dry and shrivel, thus reducing crop yield.
Calculate degree-days for obliquebanded leafroller in your location.
Learn to use degree-days to time insecticide applications.
Spring treatments of young caterpillars with Bacillus thuringiensis or spinosad and monitoring with pheromone traps to time summer applications are the key approaches to monitoring this pest in pistachio.
There are several parasite species (Macrocentrus iridescens, Bracon sp. and Goniozus sp.) that attack obliquebanded leafroller and can significantly reduce its populations in the second and third generations. None of these parasitoids are commercially available (the Goniozus species that attacks obliquebanded leafroller is not G. legnei).
Organically Acceptable Methods
Springtime sprays of Bacillus thuringiensis and summer spray of the Entrust formulation of spinosad are acceptable for use in an organically managed orchard.
Monitoring and Treatment Decisions
To time summer treatments, put out pheromone traps by mid-April (Kern and King counties) and April 25 from Fresno north. In addition, look for obliquebanded leafroller larvae when traps indicate adults have emerged. Examine trees for leaf rolls, leaves tied together, and live larvae. When male moths are first found in traps, begin degree-day calculations (upper threshold 94°F, lower threshold 43°F). Treat when 800 degree-days have accumulated.
UC IPM Pest Management Guidelines:
Insects and Mites
Acknowledgment for contributions to Insects and Mites: