Cultural control methods improve management of leafhopper vector of X-disease

Authors: Marshall, Adrian; MELTON, TAWNEE - Washington State University; BISHOP, GARRETT - Gs Long Company; CLARKE, ABIGAIL - Washington State University; REYES-CORRAL, CESAR - Washington State University; CATRON, KATLYN - Washington State University; NOTTINGHAM, LOUIS - Washington State University; NORTHFIELD, TOBIN - Washington State University

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/29/2023
Publication Date: 10/5/2023
Citation: Marshall, A.T., Melton, T.D., Bishop, G., Clarke, A.E., Reyes-Corral, C., Catron, K.A., Nottingham, L.B., Northfield, T.D. 2023. Cultural control methods improve management of leafhopper vector of X-disease. Crop Protection. https://doi.org/10.1016/j.cropro.2023.106445.
DOI: https://doi.org/10.1016/j.cropro.2023.106445

Interpretive Summary: A pathogen known as X-disease phytoplasma which causes fruit loss and leads to tree death in cherries that is transmitted by leafhoppers has recently reached epidemic levels in the Pacific Northwest, USA. Management strategies for X-disease are outdated (1980's) and include the sole reliance on insecticides and removing the infected trees, which is not effective and has lead to the loss of entire orchards. Researchers at the USDA-ARS in Wapato, WA and Washington State University in Wenatchee, WA investigated the use of two novel season-long organic management strategies for controlling the leafhoppers that transmit the X-disease pathogen. They found that treating trees with a clay particle film (Surround WP) or lining the orchard floor with reflective plastic (Extenday) deterred the leafhopper vectors and thus prevented the risk of X-disease. These control methods will provide growers in the pacific northwest tools to reduce the spread of X-disease, the use of insecticides, and ultimately the loss of cherry orchards.

Technical Abstract: X-disease, caused by the phytoplasma ‘Candidatus Phytoplasma pruni’, is currently threatening Pacific Northwest (USA) stone fruit (Prunus) production, particularly sweet cherry (P. avium). There is no cure, and infected fruit remain unmarketable throughout the tree’s life. Management efforts focus on reducing transmission through infected tree removal and frequent chemical applications to control the leafhopper vectors. The increase in chemical inputs has broken down stone fruit integrated pest management techniques and is neither economically nor environmentally sustainable. To investigate sustainable vector management, we assessed the efficacy of two long-lasting cultural management techniques, kaolin clay (Surround WP) and reflective plastic geotextile (Extenday), to deter leafhoppers from trees and prevent population growth within orchards. These methods were tested against untreated control plots in Washington State commercial stone fruit blocks in 2021 and 2022. Colladonus montanus reductus (Van Duzee) was the most abundant leafhopper vector species captured in both years. In cherry blocks, Extenday consistently reduced C. m. reductus densities by 80-90%, while kaolin clay caused a 45-50% reduction in leafhoppers, but only when they were abundant (more than 10 leafhoppers per trap). Sticky cards placed at varying heights revealed that kaolin clay caused C. m. reductus to be proportionally more abundant near the ground cover than in the tree canopy regardless of overall population density. The combination of reducing C. m. reductus density and shifting their distribution into the ground cover demonstrates both plastic geotextiles and kaolin clay provide effective post-harvest strategies for X-disease management.