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Eastern peach X disease

Scientific Name
Western X-disease phytoplasma
Scientific Author
(Phytoplasma: Acholeplasmatales: Candidatus: 16SrIII X-disease group)

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Diagnostic Images

Host symptoms - fruit
Shoots from a young Rainier cherry scion/Colt rootstock tree recently infected with X-phytoplasma showing mixture of normal (left) and diseased (right) fruit (For permission to reproduce images email
Dr. JK Uyemoto USDA
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Diagnostic Images (9)
Diagnostic Notes

Bacteria; Firmicutes; Mollicutes; Acholeplasmatales; Acholeplasmataceae; Candidatus Phytoplasma; 16SrIII (X-disease group).




X-disease affected peach trees may exhibit dieback of branches early in the growing season due to increased sensitivity of the vascular tissue to cold damage in winter. Affected leaves on branches may also be smaller. Approximately six to eight weeks into the growing season, leaves on affected branches curl inward and develop irregular yellow to reddish-purple spots, which later become dry and brittle and drop out leaving tattered leaves with a "shot hole" appearance. Leaves on affected branches fall prematurely, starting at the base of the branch, and often leave a cluster of leaves at the tip of the branches. Yield and quality of the fruit are affected. Fruit can drop prematurely, while remaining fruit can colour and ripen prematurely and have a bitter taste. In the early stages of disease development, only a few branches are affected. However, the entire canopy of an X-disease affected peach tree will show symptoms two to three years after initial infection. Up to 60% disease incidence in an orchard has been reported. Yield reduction as high as 80% has been reported from severely affected orchards. X-disease affected peach trees gradually decline and trees may die within 2-6 years (Nemeth, 1986; Kirkpatrick et al., 1995).


The X-disease phytoplasma is associated with Cherry X-disease (also known as cherry buckskin) in sweet cherry and sour cherry. Symptom development in cherry depends on the cultivar and rootstock combinations. Cherry trees on Mahaleb rootstocks decline quickly and die. Trees on Mazzard, Colt, and Stockton Morello rootstocks decline slowly and may survive for many years, however a severe reduction in yield occurs (Uyemoto, 1989; Kirkpatrick et al., 1995). Affected fruit may be small and pale and fail to ripen. Affected fruits may be mixed on the same branch with unaffected fruit. Leaves on the shoot tips may form a rosette and become bronze or rust coloured several weeks earlier than leaves on healthy trees. In sour cherries, dieback may affect older infected twigs and branches.  In many cherr

More Information
Specimen Contact
Fiona Constable
Constable FE & Gibb KS
14/08/2006 06:36 AEST
Last Updated
21/10/2011 09:32 AEST
Constable FE & Gibb KS (2006) Eastern peach X disease (Western X-disease phytoplasma) Updated on 10/21/2011 9:32:02 AM Available online: PaDIL -
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Free for use under the Creative Commons Attribution 3.0 Australia License