X-disease phytoplasma and little cherry virus 1 and 2 have resulted in substantial loss of stone fruit acreage in Washington and Oregon. The extent and financial impact on the industry was not previously known. A Washington and Oregon State University survey documented 238,856 trees equivalent to 974 acres of sweet cherries removed due to X-disease and little cherry disease between 2015 and 2020. Removed trees reduced revenue to the industry by an estimated $30 million in 2020 and $65 million between 2015 and 2020. Over the seven-year re-establishment period estimated lost revenue and establishment costs to growers is an estimated $115 million.

Chokecherry (Prunus virginiana L.) is a native shrub that is widely found across North America and is a host of ‘Candidatus Phytoplasma pruni’ associated with X-disease of stone fruits. This pathogen is of major concern to U.S. cherry and peach growers, with the most recent and ongoing outbreak in the Pacific Northwest causing major economic harm. To investigate the role of chokecherry as a potential reservoir and source of orchard-associated strains, we surveyed wild chokecherry trees across 12 U.S. states, and compared the strains present to those in commercially cultivated Prunus species. Approximately 47% of chokecherry sampled tested positive for a ‘Ca. P. pruni’-related strain and phylogenetic analysis revealed high strain diversity, including six distinct clades and four newly identified lineages. In contrast, ‘Ca. P. pruni’ strains isolated from cultivated cherry and peach trees exhibited lower diversity and were infected by known disease outbreak-associated strains such as NWX. These data suggest limited transmission between wild and cultivated hosts in the western U.S., with patterns indicating spillover from orchards into nearby chokecherry populations rather than the reverse. However, in states east of the Rocky Mountains, chokecherry likely functions as a reservoir for orchard infections.

Quince ‘Eline’ (Cydonia oblonga L.) is a cold-hardy rootstock for pear (Pyrus communis L.) that could potentially be adopted by the U.S. pear industry if it can be shown to perform under conditions that have prevented prior quince rootstock adoption. These conditions include colder winters and hotter, drier summers than the European regions where quince ‘Eline’ is currently used. Preplant soaking, the practice of submerging bare-root tree roots in water to rehydrate them following cold storage, will potentially be a critical component of preventing transplant shock if pear orchards grafted to quince ‘Eline’ are to be established in hot or dry areas. This study tested five soaking treatments for ‘Bartlett’ pear grafted on quince ‘Eline’ with a ‘Beurre Hardy’ pear interstem, and measured multiple factors related to tree establishment success throughout the first growing season. The treatments included a 0 h control as well as 24, 48, 72, and 96 h soaking times. The tree weight decreased when not soaked and increased when soaked for 48 or 72 h. Tree health remained similar among the soaking treatments, with all trees surviving, though the health assessment was limited by the use of an ordinal scale. The growth varied, with the 24, 48, and 72 h treatments showing the greatest trunk cross-sectional area and leader length increase. Stomatal-conductance-to-water-vapor measurements, used as a proxy for tree water stress, showed that the 96 h treatment resulted in more highly stressed trees. Altogether, this study identifies the benefit of preplant soaking for ‘Bartlett’ grafted to quince ‘Eline’, and highlights the 24 to 72 h range as a best practice for establishment for U.S. pear growers.