Biological Activity, Residue Analysis and Dietary Risk Assessment of Five Non-Conventional Insecticides in Cowpea

In recent years, the problem of pesticide residues in cowpeas remains a challenge, prompting comprehensive management efforts nationwide. Therefore, the analysis of pesticides has become an important research field, especially for new pesticides developed recently. The present study was undertaken to investigate the residual activity of five non-conventional insecticides (abamectin, emamectin benzoate, imidacloprid, indoxacarb and spinosad), on the development of cowpea weevil, Callosobruchus maculatus at different periods of storage on treated cowpea seeds and the potential dietary risk of tested insecticides through cowpeas to consumers. Residual activity of tested insecticides on C. maculatus adults exposed to cowpea seeds treated with high concentration (equal 24h-LC90) at different storage intervals was assessed. The adult mortality of C. maculatus decreased from 95, 98.5, 90, 89 and 90 % (at Zero-day of storage) to 40, 43, 50, 45 and 43% (at 90-day of storage) for abamectin, emamectin benzoate, imidacloprid, indoxacarb and spinosad, respectively. Among the five tested insecticides, abamectin, emamectin benzoate and Spinosad seemed to be more effective. The residual content of tested insecticides gradually decreased over time. In addition, data indicated that spinosad and emamectin benzoate were relatively more stable on cowpeas up to the 120 days storage interval. Data showed that all the Target hazard quotient (THQ) values for each insecticide from the consumption of treated cowpea was less than one (<1.0) suggesting that the associated health hazard with exposure to any of these insecticides, applied at selected concentrations, is insignificant for both human adults and children.