Getting Ahead of X-disease

Authors: THOMPSON, ASHLEY - Oregon State University; ADAMS, CHRISTOPHER - Oregon State University; Reinhold Aboosaie, Lauri; PSCHEIDT, JAY - Oregon State University

Submitted to: Oregon State University Extension Publications
Publication Type: Other
Publication Acceptance Date: 1/1/2022
Publication Date: 8/17/2022
Citation: Thompson, A., Adams, C., Reinhold, L.A., Pscheidt, J.W. 2022. Getting Ahead of X-disease. Oregon State University Extension Publications. EM9362.

Interpretive Summary: X-disease, caused by the phytoplasma ‘Candidatus Phytoplasma pruni’, has been documented in the Pacific Northwest since the early 1930s. Since then, outbreaks of X-disease have emerged every 20 years or so. Understanding X-disease and identifying and removing infected trees will help break this cycle. Sweet cherry trees infected with X-disease produce unmarketable little, pointed fruit that does not ripen. The X-disease phytoplasma can rapidly spread from tree to tree through leafhoppers and by grafting between roots. Once infected, a tree may not show symptoms for two years, but it will be contagious. X-disease can eventually kill an infected tree. Since X-disease cannot be cured, reducing new infections in an orchard requires prompt detection and tree removal. This publication will help orchardists and field representatives identify X-disease-infected trees, remove X-disease-infected trees and control infection in orchards confidently and efficiently.

Technical Abstract: X-disease, caused by the phytoplasma ‘Candidatus Phytoplasma pruni’, has been documented in the Pacific Northwest since the early 1930s. Unfortunately, X-disease has become a cyclic problem on the West Coast as outbreaks of X-disease emerge every 20 years or so. Understanding X-disease and identifying and removing infected trees will help break this cycle. Sweet cherry trees infected with X-disease produce unmarketable little, pointed fruit that does not ripen. The X-disease phytoplasma can rapidly spread from tree to tree through leafhoppers and occasionally by root grafts. Once infected, a tree may not show symptoms for two years, but it will be contagious. X-disease can eventually kill an infected tree. X-disease is an economically significant disease of sweet cherries. The 1931 X-disease outbreak in Napa and Sonoma counties in California destroyed the sweet cherry industry in that region. The Rogue Valley, Oregon, cherry industry suffered a similar fate in the 1950s. A later outbreak in California demonstrated that tree removal is the best way to reduce new X-disease infections. Since X-disease cannot be cured, reducing new infections in your orchard requires prompt detection and tree removal. This publication will help orchardists and field representatives identify X-disease-infected trees, remove X-disease-infected trees and control infection in orchards confidently and efficiently.