Abstract

Entomotoxic effects of powder and oil from the leaves and seed of Hura crepitans (L.) on Callosobruchus maculatus (F.) was investigated at the Pest Management Laboratory in the Department of Crop, Soil and Pest Management, the Federal University of Technology Akure, Ondo State, Nigeria under prevailing laboratory conditions of 28±3°C temperature and 65 ± 5% relative humidity. The powders from the leaves and seeds of H. crepitans were applied singly at the rates of 1, 2 and 3 g per 20 seeds weighed into sterile Petri dishes and infested with 5 pairs of one day old C. maculatus adults in three replicates. The oils were applied at the rates of 1, 2.5 and 5 ml per 1 kg of seeds respectively in 3 L plastic containers by injecting the oils into 1 kg of seeds with a syringe and 20 seeds selected randomly from each container into Petri dishes in three replications including the controls. The oil-treated seeds were infested with 5 pairs of a day old adults of C. maculatus. Data were collected on number of dead C. maculatus adults, number of eggs laid, number of seeds with eggs, seeds without eggs, number of emerged aduls, number of seeds with holes, seeds without holes and weight loss after 12, 24 and 48 h of application of powders and oils. The results from the study showed that H. crepitans powders and oils caused mortality in adult C. maculatus. The mortality (80%) of adults C. maculatus at 48 h after application was significantly higher (P<0.05) in cowpea seeds treated with 2 g of seed powder. Application of H. crepitans significantly reduced (P<0.05) oviposition (4.58) at 2 g of the seed powder applied on cowpea seeds. The number of emerged adults (0.71) was significantly lower (P<0.05) on cowpea seeds treated with seed powder and seed oil at higher rates. Weight loss (0.08) was significantly lower in cowpea seeds treated with 2.5 and 5 ml of seed oil. Therefore, based on these results, H. crepitans could be explored as an alternative biopesticide to synthetic insecticide in the protection of stored cowpea against C. maculatus (F.).

Key words: Hura crepitans, Callosobruchus maculatus, entomotoxic, assessment.