X-Disease epidemic and vector management update

A recently re-emerged leafhopper vectored disease, X-disease caused by the phytoplasma Candidatus Phytoplasma pruni, is jeopardizing commercial stone fruit (cherry, peach, nectarine) production in the Pacific Northwest region of the United States. Common groundcover weeds such as clover and dandelion have been listed as disease hosts and may serve as leafhopper feeding hosts, suggesting that groundcover weeds may promote disease prevalence in orchards. From 2020-2021 we evaluated two methods, plastic groundcover and particle film sprays, to reduce vector abundance and dispersal. Leafhopper densities were significantly lower in both treatment plots than controls each year. Furthermore, trap counts suggest greater movement in the treated blocks in the ground cover at (0.5m) rather than at tree canopy heights (2m), whereas in control plots we observed high leafhopper capture in 2m traps. No-choice laboratory assays determined leafhoppers will land on clay covered cherry leaves, suggesting that leafhoppers can recognize and feed on leaves coated with particle film, so field effects are likely driven by deterrent effects than an inability to recognize and locate plants. These results demonstrate the potential of two season-long cultural techniques for improving control of the leafhopper vectors and disrupting the source-sync dynamics of X-disease phytoplasma.