Western x-disease

a Spiroplasma

Hosts

Chokecherry and other Prunus spp.

Distribution and Disease Cycle

Description of this image follows
Foliar chlorosis and reddening on foliage of X-disease infected chokecherry.
Photo credit: OMAFRA (Ontario Ministry of Agriculture, Food, and Rural Affairs

Western X-disease is caused by a pathogen called a spiroplasma, a mycoplasma-like organism which is transmitted from infected to healthy plants by several species of leafhopper as they feed on the leaves. Feeding occurs from May to October, but disease transmission generally only occurs from June to September. Disease symptoms usually become apparent the season following infection. The disease can spread rapidly and kill a plantation in only 3 or 4 years. While this disease is economically significant for many stone fruits (peach, nectarine, sweet and sour cherry) in Canada, this disease is currently of minor importance on the prairies.

Symptoms and Signs

Description of this image follows
A chokecherry plant with the early leaf coloration symptoms of the X-disease infection.
Photo credit: H.J. Larsen, Bugwood.org

Plants infected by Western X-disease often have reduced growth and eventually begin to decline and die. Infected leaves become yellowish in late-June, sometimes with a reddish margin, turning a deep red by summer. Infected fruit become pointed and off colour (yellow red rather than deep red), becoming unsuitable for jams and jellies and their seeds will not germinate.

Control

Remove all infected shrubs and burn or bury immediately after removal. All infected shrubs may not exhibit symptoms however, so complete eradication may not be possible. Chemical leafhopper control may be required, but removing weed cover for leafhoppers will also help reduce pest populations. Do not establish nurseries containing chokecherries, cherries or plums near chokecherry shelterbelts or wild populations of chokecherry. There are no chemical control options for Western X-Disease.

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