Association of bean rust and common bacterial blight epidemics with cropping systems in Hararghe highlands, eastern Ethiopia

Surveys of common bean rust and common bacterial blight (CBB) diseases were conducted in the Habro, Chercher and Wobera. areas of the Hararghe highlan ds, Ethiopia during the 1998 and 1999 cropping seasons in four different be an cropping systems, Intercropping constituted 91% of the cropping systems. Bean proportions in intercropping ranged from 13 to 55%. In intercropping, the mean rust incidence and severity was reduced by 25 and 16%, respective ly, compared with sole cropping. Similarly CBB incidence was reduced by 29% while severity was reduced by 20%. Single and multiple variable logistic r egression analyses were used to determine the association of rust and CBB d iseases with cropping systems and practices, geographical areas, cropping y ears and altitude. The analyses indicated that cropping system, geographica l area and cropping year were important variables and affected both rust in cidence and severity. In Habro during 1998 there was a high probability of rust incidence and severity greater than 25%. The probability of rust incid ence and severity exceeding 25% in Habro was about 11 and 4 times greater t han in Chercher and Wobera areas, respectively. Less than 50% bean proporti ons in intercropping were significantly associated with low (< 25%) rust se verity, Similarly geographical area, altitude and cropping system affected CBB incidence and severity. In Habro and at lower altitudes there was a hig h probability of greater than 25% CBB incidence and severity. Bean plants a t podding and or maturity were closely associated with high rust and CBB se verity. Intercropping systems were more associated with lower CBB and rust intensity than sole cropping.