Studies on the control of major insect pests and yield of cowpea (Vigna Unguiculata (L) Walp under calendar and monitored application of synthetic chemical in ABRAKA, Southern Nigeria

摘要

The application of insecticides by farmers to curtail the menace of insect pests of cowpea, sometimes may be as high as 8 to 10 times in the growing season. Experiments were conducted in the early and late planting seasons of cowpea, on a public land ½ kilometre to Campus II, Delta State University, Abraka, Nigeria. The study aimed at reducing the number of times chemicals were applied to control four major insect pests of cowpea and influence on yield. Insect pests studied were the cowpea aphid, Aphis craccivora Koch, legume bud thrips Megalurothrips sjostedti Tryb, legume pod borer, Maruca vitrata Fab. and pod sucking bugs. Fixed number of sprays - calendar sprays - 5 times at 7 days’ intervals (CA.S7) and 4 times at 10 days’ intervals (CA.S10) and monitored sprays (MOS) sprayed only when insect pests damage/infestation reached action threshold, were compared to determine their effect on insect pest number and yields. The results revealed that cypermethrin in the different treatments effectively controlled A. craccivora and M. sjostedti in the early season. During the late season, the chemical was effective on the major insect pests. Yields were 2,886.20kg ha-1, 2,349.20kg ha-1, 2087.20kg ha-1 for MOS, CA.S7 and CA.S10 respectively in the early season. In the late season, yields were 1,814.00kg ha-1 1787.40kg ha-1 and 1577.00kg ha-1 for CA.S10, CA.S7 and MOS respectively. The study provides the information that (i) the calendar schedules - 7 and 10 days’ and monitored sprays were not significantly different in their effect on insect pest number and yield (ii) CA.S10 and monitored sprays could be beneficial to cowpea farmers as this practice would reduce number of chemical application, cost and environmental pollution