Management of major field insect pests and yield of cowpea (Vigna unguiculata (L) walp) under calendar and monitored application of synthetic chemicals in Asaba, southern Nigeria

Abstract

The management of major field insect pests of cowpea under calendar and monitored sprays of cypermethrin was studied. The major insect pests studied were the co wpea aphid, Aphis craccivora Koch, legume bud thrips Megalurothrips sjostedti Tryb, legume pod borer, Maruca vitrata Fab. and pod sucking bugs. Influence of insect pe st management on yield was also determined. The calendar sprays consisted of 7 days' spray intervals carried out 5 times and 10 d ays' spray intervals, carried out 4 times. Monitored spray was carried out only when insect pest infestation/damage reached or exce eded the action threshold. The experiments were conducted in the Teaching and Research Farms of the Agronomy department, Asaba Campus, Delta State University, Nigeria. Comparison of insect pests and grain yield from the calendar and monitored spray treatments was made if differences existed among them. Results indicated that all the cypermethrin treatments effectively c ontrolled M. sjostedti , M. vitrata , flower bud thrip population and pod sucking bugs when compared to control in the early season. Ther e was however, no significant difference (P>0.05) in calendar and mon itored sprays. Similar observation was made for gr ain yield. In the late season, all treatments significantly (P<0.05) contr olled pest population/damage on cowpea. Grain yiel d increase was similarly recorded but no differences among the treatments. Cowpea growers sometimes apply insecticides as many as 8 to 10 times to control insect pests during the growing season; the study here provides evidence (1) that 10 days' int erval spray and monitored spray can be as profitable as 7 days' interval spra y in cowpea production and (2) this could reduce th e number of chemical application, save cost as well as environmental pol lution and hazards to consumers.