Toxicity of Single and Mixture Application of Afrostyrax lepidophyllus and Afromomum melegueta Seed Powder on the Biology of Cowpea Bruchid, Callosobruchus maculatus (F.)

Abstract

The study investigated effect of Afrostyrax lepidophyllus (Af) and Afromomum melegueta (Am) seed powders and their mixtures on aspects of the cowpea bruchid Callosobruchus maculatus Fabr biology. Twenty grams each of the cowpea seeds were placed in 5 transparent plastic containers labeled A-E, with E as the control. Ten (10) pairs of 1-2 days old adult C. maculatus were introduced into each set up and treated with four different ratios (Af:Am) of the powdered materials as follows; (60%:40%), (40%:60%) (100%:0%) and (0%:100%) and a control (0%:0%). Each treatment was replicated 4 times and arranged in a randomized complete block design (RCBD). The bruchids were allowed to feed, mate and oviposit for six days and monitored for Adult mortality. For ovipostion and adult emergence, 5 pairs of male and female bruchid introduced into containers with 10 seeds of cowpea. The treatments exhibited concentration and exposure time dependent toxicity. The 100%:0% application was the most toxic, causing 100% adult mortality within 4 days of post treatment with 1.5 g /20 g cowpea seeds. All other concentrations also caused significant (P<0.05) adult mortality 5 days post treatment. The treatment 60%:40% significantly deterred oviposition (P<0.05) and was the only treatment with noticeable oviposition deterency. The treatment 100%:0% recorded the lowest adult emergence (23.21%). The result indicates that sole application of                    A. lepidophyllus was more effective in protecting cowpea seeds against C. maculatus than the mixtures.