Identifying Biocontrol Agents for X-Disease Vectors to Allow Integrated Pest Management in Cherries: Final Report

X-disease (little cherry disease) is a major threat to Pacific Northwest cherry production, and management largely relies on removing infected trees and chemically controlling leafhopper vectors. This final BIOAg report documents development and deployment of molecular tools to support integrated pest management by quantifying natural enemies of key vectors, Colladonus montanus reductus and Colladonus geminatus.

The team validated primers for a parasitic fly (Tomosvaryella lepidipes) and a Hirsutella fungus (validated to genus), and developed broader Dryinid wasp primers after taxonomic uncertainty limited species-level identification. They built a five-target multiplex assay to simultaneously identify vector species, detect parasitism (fly and Dryinids), and test for X-disease phytoplasma. Field sampling across Washington (47 sites; four tree fruits) produced more than 2,000 leafhoppers for screening and revealed geographic patterns in vector abundance. Results show measurable parasitoid attack rates, rare phytoplasma positives, and evidence that Hirsutella is a vertically transmitted symbiont associated with Colladonus species.