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Pseudomonas syringae pv. syringae Associated with Apple and Pear Buds in South Africa. E. Lucienne Mansvelt, Fruit and Fruit Technology Research Institute, Private Bag X5013, Stellenbosch 7600, South Africa. M. J. Hattingh, Department of Plant Pathology, University of Stellenbosch, Stellenbosch 7600, South Africa. Plant Dis. 71:789-792. Accepted for publication 4 February 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0789.

Starkrimson and Granny Smith apple buds from orchards with a history of blister bark and Packham's Triumph pear buds from orchards with a history of blossom blast were examined for the presence of Pseudomonas syringae pv. syringae. The bacterium was detected inside apparently healthy buds during growing and dormant seasons over a 2-yr period. Individual bud scales were colonized, and the greatest populations of P. s. pv. syringae were evident during fall and spring. Epiphytic populations of the pathogen occurred on Starkrimson buds at the green-tip growth stage and on Packham's Triumph at the budbreak stage. No or few bacteria were detected on buds of cultivar Granny Smith. More pear than apple budwood contained P. s. pv. syringae. The organism probably overwinters in dormant buds. Apple blister bark or pear blossom blast is therefore likely to develop if symptomless buds from infected trees are grafted onto rootstocks in new plantings.

Keyword(s): epidemiology.