Effect of weed removal on insect populations and yield of Cowpea [Vigna unguiculata (L) Walp]

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Australian Journal of Agricultural Engineering


Field studies were conducted during the cropping seasons of 2008 and 2009 at Ilorin, Nigeria to evaluate the influence of weed removal on insect population and yield of cowpea [Vigna unguiculata (L) Walp]. The trial was designed as a randomized complete block in a split-plot arrangement and three replications. The main plots were two cowpea varieties while the sub plots were three weeding regimes (no-weeding, 1 hand weeding at 3 weeks after sowing and 2 hand weeding at 3 and 6 weeks after sowing). The cowpea varieties were similar in most of the parameters assessed. Reduced cowpea biomass, pods and grain yield were associated with weedy cowpea plots. Grain yield reduction due to uncontrolled weed growth was estimated to be 50-60 % and 70-80 % compared to one-hand weeding and two-hand weeding, respectively, while a yield reduction of 30-60 % in one-hand weeding compared to two-hand weeding. Weedy situation in the cowpea ecosystem supported higher insect population whereas Aphis craccivora Koch and Empoasca spp. population increased when the crops experienced weed-free situation because of the influence of groundcover on the optomotor landing response of the aphids and probably due to reduction in natural enemies of Empoasca spp. It is concluded that a search for alternative methods of Pests Management, which entails a quantitative understanding of the dynamics of weed and insect population outflow in cowpea agroecosystem in the humid tropics is needed for a profitable cowpea production.



cowpea;, Empoasca spp, Aphis craccivora Koch, yield