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Induced Resistance to Cytospora in Bearing Trees of Prunus domestica. A. W. Helton, Plant Pathologist, Department of Plant Sciences, University of Idaho, Moscow 83843; J. W. Braun, Former Graduate Fellow, Department of Plant Sciences, University of Idaho, Moscow 83843. Phytopathology 61:721-723. Accepted for publication 26 January 1971. DOI: 10.1094/Phyto-61-721.

Eight-year-old Italian prune (Prunus domestica) trees were inoculated with Cytospora cincta early in the growing season, and groups of these trees (three in a group) were reinoculated once at intervals throughout the remainder of the growing season. The results showed that (i) the maximum canker size achieved prior to the onset of marginal healing varies directly with the initial vigor of the individual Cytospora invasions; and (ii) invasion of bearing Italian prune trees by Cytospora fungi induces a resistance reaction in vivo which is detectable as far as 120 cm away from the initiating infection, and appears to be truly systemic in nature.