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Overwintering and Survival of Pseudomonas syringae pv. syringae and Symptom Development in Peach Trees. Elke Endert, Graduate Research Assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27650. David F. Ritchie, Assistant Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Plant Dis. 68:468-470. Accepted for publication 14 December 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-468.

Peach trees (cultivar Redhaven) were inoculated in October 1981, when leaves were 510% abscised, and again in February 1982 with a suspension (107 colony-forming units per milliliter) of a rifampin-resistant strain of P. syringae pv. syringae (rif 2). Inoculum was applied by either brushing the bacterial suspension onto the surfaces of buds and leaf scars (SI) or by injecting it into internodal punctures (PI). Internal populations of rif 2 were monitored biweekly by plating onto a semiselective medium. October SI resulted in rapid initial colonization followed by a decline in rif 2 populations to below detection levels, whereas October PI resulted in stable population levels throughout the following winter and spring. No internal colonization was detected in February SI sites. In contrast, February PI resulted in larger populations than did October PI and were accompanied by the development of cankers at 98.8% of the inoculated sites. February PI infections were also associated with necrosis of fruit and shoot buds and delayed budbreak. Populations of rif 2 remained viable within February PI sites throughout the summer and fall. Rif 2 could not be reisolated as part of the epiphytic twig, shoot, or blossom flora in March.

Keyword(s): bacterial canker, peach tree short life, Prunus persica.