Protective netting as a barrier against the X-disease phytoplasma vector Colladonus reductus in cherry orchards

Authors: Marshall, Adrian; Harper Jr, Douglas; Cooper, William; Pitino, Marco

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2026
Publication Date: 4/21/2026
Citation: Marshall, A.T., Harper Jr, D.W., Cooper, W.R., Pitino, M. 2026. Protective netting as a barrier against the X-disease phytoplasma vector Colladonus reductus in cherry orchards. Journal of Economic Entomology. 2026: toag109. https://doi.org/10.1093/jee/toag109.
DOI: https://doi.org/10.1093/jee/toag109

Interpretive Summary: A current outbreak of X-disease (aka little cherry disease) is devastating the cherry and stone fruit industry of Washington State. The pathogen responsible for X-disease, Phytoplasma pruni, is transmitted by leafhoppers, especially Colladonus reductus in Washington. Growers must rely on pesticide applications to control the leafhoppers and removal of infected trees, which has proven to be ineffective and costly. Researchers at the USDA-ARS in Wapato, Washington found that agricultural netting, including some mesh sizes already used for wind and bird protection, can exclude Colladonus reductus thus stopping transmission. Results of this study help provide growers with highly effective season-long control techniques for the leafhoppers that transmit X-disease, and inform ongoing larger field trials being conducted by USDA scientists.

Technical Abstract: X-disease, caused by “Candidatus Phytoplasma pruni,” poses a significant economic threat to the stone fruit industry, causing the removal of vast cherry acreage in Washington State. The most abundant vector in these orchards is the leafhopper Colladonus reductus (Van Duzee). Growers need season-long preventative alternatives to insecticides for a robust integrated pest management program. Thus, this study evaluated the efficacy of protective netting as a barrier to C. reductus. Between 2024 and 2025, 3 field trials were conducted testing 4 types of netting (20% shade, 30% shade, Mesh 25, and Mesh 50) against a non-covered control. Trials were established in 2 cherry orchards with high levels of X-disease phytoplasma infection. Molecular analysis of the ambient vector population confirmed a 73% and 56% infection rate with ‘Ca. P. pruni’ at each orchard, respectively, highlighting severe disease pressure. Small enclosures (1.2'×'0.6'm) containing 5 potted Prunus trees (sweet cherry and peach) were monitored using yellow and clear sticky cards for C. reductus presence. Fine-mesh exclusion netting reduced C. reductus abundance by over 99%, and shade netting consistently caused a 90% reduction. These findings demonstrate a successful proof of concept that netting can serve as a physical barrier to leafhopper vectors that transmit X-disease phytoplasma. Netting should be examined in a commercial orchard setting and for effects on pathogen transmission.