VIEW ARTICLE

Ecology and Epidemiology

Cruciferous Weeds as Sources of Inoculum of Xanthomonas campestris in Black Rot of Crucifers. N. W. Schaad, Department of Plant Pathology, University of Georgia, Georgia Experiment Station, Experiment 30212; J. C. Dianese, Department of Plant Pathology, University of Georgia, Georgia Experiment Station, Experiment 30212, Present address: Departmento de Biologia Vegetal, Universidade de Brasília, Brasília, 70910 Brazil. Phytopathology 71:1215-1220. Accepted for publication 24 February 1981. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-1215.

Cruciferous weeds were studied as a potential source of inoculum of Xanthomonas campestris, the causal agent of black rot of crucifers. Four transplant farms in southern Georgia and 19 sites in the seed production areas of California were surveyed, and cruciferous weeds were found to be widespread in both states. In Georgia, black rot was found on Brassica campestris, Lepidium virginicum, Coronopus didymus, and Raphanus sativus. In California, black rot was found on B. campestris, B. nigra, B. geniculata, R. sativus, and Cardaria pubescens. Three of the seven sites in California where black rot was found in weeds were associated with a cultivated crop of crucifers. Field plot data in Georgia showed that X. campestris was disseminated up to 12 m from infected weeds to cabbage. These results may explain the unusually high levels of black rot found in transplant and seed fields in the last 10 yr. More attention should be paid to controlling cruciferous weeds in transplant and seed production fields.