Association of Phytophthora syringae with Pruning Wound Cankers of Almond Trees. R. M. Bostock, Assistant Professor, Department of Plant Pathology, University of California, Davis 95616. M. A. Doster, Graduate Research Assistant, Department of Plant Pathology, University of California, Davis 95616. Plant Dis. 69:568-571. Accepted for publication 8 January 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-568.

Cankers on almond trees with profuse gumming associated with pruning wounds were frequently observed in California orchards during the winters and springs of 1982–1984. These cankers frequently girdled and killed limbs less than 5 cm in diameter. Phytophthora syringae was isolated with high frequency from these cankers in April but not in June, and its pathogenicity to pruning wounds was proved by artificial inoculations in February. Nearly all cankers caused by P. syringae were associated with pruning wounds or injuries created during pruning in late autumn and winter. No other known pathogens of almond were isolated from pruning wound cankers. Excised branch pieces inoculated with P. syringae developed cankers at temperatures between 2 and 20 C.