EFFECTS OF SOWING DATES AND SCAB DISEASE ON YIELD OF COWPEA (VIGNA UNGUICULATA L. WALP).

Abstract

Effects of sowing dates on incidence and severity of scab disease and yield of cowpea was investigated at Samaru, Zaria, Nigeria using five cowpea varieties; SAMPEA 6, SAMPEA 8, SAMPEA 11, TVx 3236 and Ife Brown. Seeds were sown at three planting dates at 10 day intervals, August 9, 19 and 29 in 2016. Treatments were arranged in a Randomised Complete Block Design (RCBD) with three replications. Cowpea varieties showed varying degrees of scab infection. Crops sown on August 9 had higher scab incidence, 14 % to 80 % and severity, 17.33 % to 42.40 % while there was no scab infection observed on the August 29 sown crops. Path coefficient analysis showed that highest individual contribution of scab severity on yield was by pod (18.94 %), followed by flower cushion (16.42 %). Scab severity on stem had highest direct effects (-0.435) while highest indirect effects was scab severity on stem via peduncle (-0.364). Cowpea scab caused yield reduction of 36 %. The varieties, SAMPEA 6, SAMPEA 8 and Ife Brown were susceptible to scab while TVx 3236 and SAMPEA 11 were moderately resistant. Highest seed yield was recorded for August 9 sown crop (1,792.60 kg/ha), followed by those sown on Aug 29, (1,422.20 kg/ha), while cowpea sown on Aug 19, had the lowest (1,192.60 kg/ha). SAMPEA 11 had the highest yield of 1691.4 kg/ha while SAMPEA 6 had lowest, 1395.1 kg/ha. The combination of moderately resistant varieties and sowing dates had profound effect on disease development and yield; this could form an integral part of disease management in scab endemic areas.