Black Rot of Crucifers in Thailand. N. W. Schaad, Associate Professor, Department of Plant, Soil and Entomological Sciences, University of Idaho, Moscow 83843. N. Thaveechai, Graduate Student, Department of Plant, Soil and Entomological Sciences, University of Idaho, Moscow 83843. Plant Dis. 67:1231-1234. Accepted for publication 16 May 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-1231.

Twenty-five crucifer fields in eight provinces in Thailand were surveyed for black rot between 7 July and 15 August 1982. Xanthomonas campestris pv. campestris was isolated from plants with symptoms of black rot and pseudomonads and erwiniae, from plants with soft rot. Twenty-eight strains of X. campestris were recovered from 21 fields. Three strains of Pseudomonas sp. and four strains of Erwinia sp. were recovered. X. campestris was isolated from one of five locally obtained commercial crucifer seed lots. No cruciferous weeds were observed in or around crucifer fields. Isolation of X. campestris from seed together with failure to observe cruciferous weeds plus the knowledge that X. campestris does not survive in soil in the humid tropics of Thailand suggest use of black-rot-free seeds and a 1-yr crop rotation for control of black rot of crucifers in Thailand.