Influence of season and cropping system on occurrence of cowpea diseases in Uganda

An on-farm survey was conducted for two seasons (first and second rains of 1994) to determine influence of season and cropping systems on occurrence of cowpea (Vigna unguiculata) diseases in Uganda. Viral diseases were widespread in both seasons but were more severe in the intercropped than in the nonintercropped cowpea. In contrast, scab, rust, and powdery mildew were less common and less severe when cowpea was grown in intercrops. High plant populations favored scab and anthracnose, but viral diseases were more severe under low plant populations. Higher incidence and severity of viral diseases, anthracnose, and scab were recorded during the first (wetter) season than during the second (drier) season. Disease level varied considerably among the common cultivars, but these differences may have been influenced by environmental differences.