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The Role of Weeds in Survival of Pseudomonas syringae pv. phaseolicola in Northern Tanzania. R. B. Mabagala, USDA-ARS and Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. A. W. Saettler (deceased), USDA-ARS and Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Plant Dis. 76:683-687. Accepted for publication 21 January 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0683.

Of 16 weed species belonging to 10 families, only Neonotonia wightii served as a perennial reservoir of Pseudomonas syringae pv. phaseolicola, the cause of halo blight. The weed survived dry periods along fences and hedgerows, by roadsides, on ditch banks, and in corners of farmersí fields. Only race 1 of P. s. phaseolicola was recovered from N. wightii. With artificial inoculation, however, all three races of the bacterium caused lesions in the weed. Because race 1 of P. s. phaseolicola was not seedborne in N. wightii, the weed cannot spread the pathogen into new areas by means of seed dispersal.