Developing a Sustainable Spraying Regime for Cowpea Seed Production in South West Nigeria

Abstract

Cowpea (Vigna unguiculata L. Walp) production in Nigeria is burdened by insect pest infestations throughout its developmental stages. Farmers rely on the use of conventional insecticides for insect pest control; however, these insecticides are often wrongly used, thereby resulting in undesirable effects on seed yield and the ecosystem. Cowpea was cultivated under different insecticide application regimes and its effect on seed production was evaluated at three substations of the Institute of Agricultural Research and Training, located at Ibadan in Oyo state (Rain forest transiting to derived savannah), Ilora in Oyo state (Derived savannah) and Ballah in Kwara state (Southern Guinea savannah). The trial was conducted during the cowpea cropping seasons of year 2018 and 2019. Ten treatments included 10 sprays of 2.5 EC lambda-cyhalothrin and cowpea varieties Ife Brown and IT2246. The experimental layout was split-split plot in a randomised complete block design. The results show a reduction in percentage aphids infestation as the spraying regimes increased on both cowpea varieties. The lowest values of 1.53 and 1.58% on Ife Brown and IT2246 respectively, were recorded on 200m/ha of four regime spray. Similar results were recorded on the number of thrips, the population of Clavigralla spp and number of pods/plant. Average seed yield under 3 spraying regime increased for both Ife Brown and IT2246 with increase in concentration of pesticide across locations except Ibadan where the yield reduced when the concentration was increased to 600 ml/ha. The spraying regimes of Lambda-cyhalotrin at foliage, flowering and podding have considerable potential for managing the pest of cowpea, but their impact of cowpea grain yield varies significantly.