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.
Marshall et al. (2026) studied this question.