Insecticide and repellent tests on Washington leafhopper vectors of cherry X-disease

Authors: Marshall, Adrian; CATRON, KATLYN - Washington State University; ORPET, ROBERT - Washington State University; CURTISS, ROBERT - Washington State University; NORTHFIELD, TOBIN - Washington State University; NOTTINGHAM, LOUIS - Washington State University

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/3/2025
Publication Date: 9/23/2025
Citation: Marshall, A.T., Catron, K., Orpet, R., Curtiss, R., Northfield, T., Nottingham, L. 2025. Insecticide and repellent tests on Washington leafhopper vectors of cherry X-disease. Journal of Economic Entomology. 118(6):2699-2709. https://doi.org/10.1093/jee/toaf247.
DOI: https://doi.org/10.1093/jee/toaf247

Interpretive Summary: X-disease phytoplasma is a pathogen that causes fruit loss and tree death in cherries and it is spread by leafhoppers. X-disease has recently reached epidemic levels in the Pacific Northwest, USA and it is estimated to have already cost the industry over $120 million in crop loss and reestablishment expenses. The last outbreak of X-disease was in the 1980's in California which has left growers with outdated (>40 years) management strategies and recommendations for insecticides that are no longer in use. In an effort to provide growers with modern product information, researchers at the USDA-ARS in Wapato, WA and Washington State University in Wenatchee, WA investigated the efficacy for leafhopper control of 23 insecticides currently approved for conventional or organic cherry production. They found chemistries that provide long lasting control of leafhoppers when applied as direct sprays, systemically, or as repellents. This efficacy information will provide growers necessary tools for reducing their current insecticide input and the spread of X-disease

Technical Abstract: A recent outbreak of X-disease, caused by the phytoplasma “Candidatus Phytoplasma pruni,” has severely harmed stone fruit production in the Pacific Northwest region of the United States. X-disease is spread by leafhopper vectors, primarily Colladonus montanus reductus in Washington and Euscelidius variegatus in Oregon. Growers rely on frequent insecticide applications and removal of infected trees, but these management recommendations originate from California when the last outbreak occurred in the 1980s. To update insecticide efficacy information for X-disease vectors, we evaluated 23 commercially available insecticidal products via direct spray, spray residues, systemic uptake by plants, or repellency assays. In direct spray bioassays, insecticides containing pyrethrins, pyrethroids, neonicotinoids, or organophosphates caused 100% mortality of C. m. reductus after 24 h. More selective chemistries including cyantraniliprole, flonicamid, and botanical essences also caused high mortality (>70%) of C. m. reductus (Van Duzee). For residues, neonicotinoids and pyrethroids caused the greatest mortality (=70%) of C. m. reductus. Systemic uptake of neonicotinoids caused significantly higher mortality (51.4% to 100%) than controls (1.4% to 32.4%) of C. m. reductus. Direct sprays and 5 d residues of neonicotinoids caused high mortality (>70%) of E. variegatus. Cherry leaves treated with either kaolin clay or diatomaceous earth had 80% to 90% fewer C. m. reductus residing on them than the controls. Overall, pyrethroids and neonicotinoids were the most effective, but more selective chemistries and repellent clays showed potential and need to be validated in field conditions. Future work should integrate insecticides, repellents, and cultural tactics with phenology-based treatment timings to improve management sustainability.