Effect of some essential oils in protecting cowpeas from cowpea seed beetle Callosobruchus maculatus (Fab.) (Coleoptera:Bruchidae)

摘要

The effect of monoterpenoid (phyllendrene, citronellol, alpha-terpineol, thymol, and citral) and ester (methylanthranillate) oils against C. maculatus adults was evaluated by topical application technique. The ester compound methylanthranillate wasmost toxic (LD50=43 #mu#g per beetle), whereas alpha-terpineol was least toxic (LD50=150 #mu#g per beetle). When piperonyl butoxide was used as a synergist, the highest and lowest synergistic effects were recorded for alpha-terpineol (synergistic ratio of 13.04) and citronellol (0.73). The effects of 1000, 2000, and 3000 ppm of essential oils, as surface protectants of cowpea seeds, on egg deposition, adult emergence, and cowpea seed weight loss were evaluated. The essential oils did not suppress insect emergence. Seeds treated with 3000 ppm citral recorded the lowest number of eggs deposited (9.33 eggs/25 seeds) and average weight loss (9.63%). All the essential oils at 3000 ppm were effective as seed protectants.