Pesticidal bioactivity of ackee (Blighia sapida Koenig) against three stored-product insect pests

Three experiments were conducted at The University of the West Indies, St Augustine Campus, Trinidad, between 1999 and 2001 to investigate the bioactivity of the dried seed powder and aril extract of ackee (Blighia sapida Koenig) on three stored-product insect pests, viz., Tribolium castaneum (Herbst.), Callosobruchus maculatus (L.), and Sitophilus zeamais Motsch. In Experiment 1, B. sapida seeds were finely ground and mixed with pigeonpea (Cajanus cajan) or maize (Zea mays) in concentrations of 0.01, 0.05, and 0.1 g (g-)1 dry weight and introduced to the three insect species for 24 h and the number of insects on the treated seeds were counted. In Experiment 2, the oviposition preferences of the males and females of each insect species to the treatments were compared to an untreated control. In Experiment 3, extracts of the aril of B. sapida were prepared using ethanol, acetone, hexane, methanol, chloroform, and water. Pigeonpea- and maize-treated seeds were offered to the three insect species for 48 h and insect mortality, number of eggs produced, and grain weight after feeding were recorded. The results showed that B. sapida powder-treated seeds affected the three insect pest species, but at varying repellency. There was at least a 50% reduction in the number of eggs oviposited for all three insect pests. The aril-water extracts induced significant (P<0.05) mortality and antifeedant effects in all three insect pests, but affected the fecundity of only C. maculatus. The other extracts showed varying degrees of success. The LC50 indicated that water is a successful extracting agent and hence could be safely used by farmers.