Eighty cowpea lines were evaluated in Uganda under natural disease pressure for resistance to Sphaceloma
sp., the causal agent of cowpea scab, during the second (short) rains of 1991 and the first (long) and second rains of 1992. Scab severity (percent plant area affected) varied with season and averaged 32% in 1991, and 2% and 24% during the first and second rains of 1992, respectively. Cowpea lines were ranked as resistant, moderately resistant, and susceptible when percent plant area affected averaged <15, 15-30, and >30 in 1991; <1.5, 1.5-4.0, and >4.0 in the first rains of 1992; and <15, 15-24, and >24 in the second rains of 1992. Overall, 25 lines were considered resistant, 20 moderately resistant and 35 susceptible.