Distribution and severity of bacterial diseases on dry beans (Phaseolus vulgaris L.) in South Africa

Disease surveys were conducted during 1995/96 in seed production fields, and 1996/97 and 1997/98 in commercial dry bean-producing areas to determine incidence, severity and spread of bacterial diseases in South Africa. A total of 682 seed production fields at 31 localities and 81 commercial fields at 24 localities were surveyed. Common bacterial blight occurred in 83 and 85% of localities in seed and commercial production areas, respectively. Halo blight was restricted to cooler production areas and occurred in only 10% of seed production fields and 37% of commercial fields surveyed. Bacterial brown spot was the most widespread bacterial disease occurring in 93% of seed production fields and 100% commercial fields. Although incidences of bacterial diseases were high, severity was generally low. The widespread distribution of bacterial diseases in both seed and commercial production areas questions the effectiveness of disease-free seed as a primary control method.