Deterrent effects of some Sri Lankan essential oils on oviposition and progeny production of the cowpea bruchid, Callosobruchus maculatus (F.) (Coleoptera; Bruchidae)

Essential oils extracted from five plant materials were tested on oviposition and progeny production of F 1 adult of cowpea bruchid, Callosobruchus maculatus on cowpea seeds. All oils tested showed a significant inhibition of oviposition and F 1 adult emergence compared to the control during no-choice tests. Cymbopogon citratus and C. nardus showed higher effect on oviposition and F 1 adult emergence than the essential oils of Alpinia calcarata, Cinnamomum zeylanicum and Murraya koinigii. In the choice test, the percentage ovipositions in all oils treated samples (except 10 mg of M. koinigii) were significantly lower than that of the control and ethanol treated samples. The percentage eggs deposited decreased with increasing doses of the oils ranging from 10 to 160 mg. The percentage of eggs laid was zero in samples treated with 40 mg of C. nardus or A. calcarata, 80 mg of C. citratus and 160 mg of C. zeylanicum. The essential oils of M. koinigii showed the lowest effect on oviposition when compared to other four essential oils.