VIEW ARTICLE

Ecology and Epidemiology

Pathogenicity on Bean of Pseudomonas syringae pv. syringae Recovered from the Phylloplane of Weeds and from Bean Crop Residue. D. E. Legard, Department of Plant Pathology, Cornell University, New York State Agricultural Experiment Station, Geneva 14456; J. E. Hunter, Department of Plant Pathology, Cornell University, New York State Agricultural Experiment Station, Geneva 14456. Phytopathology 80:938-942. Accepted for publication 30 March 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-938.

Weeds in or near fields with a history of bacterial brown spot of bean were evaluated to determine if Pseudomonas syringae pv. syringae over-winters on them. Pathogenicity of strains was determined with a detached bean pod assay. Strains of P. s. syringae were recovered from 29 of 108 and 27 of 136 samples of individual weed species collected in 1986 and 1987, respectively, but the pathogen was only recovered from two samples each year. In 1988, most samples were mixtures of weed species collected from three fields. The pathogen was recovered from 30 of 202 weed samples. Soil and bean residue from the previous season were also sampled in these fields. The pathogen was recovered from soil up to 5 June, and from bean residue throughout the season. For all 3 yr, the pathogen was recovered only from weeds at sites where brown spot had been severe the previous year. The pathogen was most frequently recovered from weeds within fields where bean residue infested with the pathogen was abundant. The pathogen was recovered from two pea samples and one soybean sample collected from sites associated with beans, not from 135 samples of 13 other crop species, and never from weeds in non-agricultural sites. For these reasons we suggest that bean residue, and not weeds, is a significant source of inoculum for bacterial brown spot in New York.