Fumigant toxicity of seven essential oils against the cowpea weevil, Callosobruchus maculatus (F.) and the rice weevil, Sitophilus oryzae (L.)

Essential oils of Tea tree (Melaleuca alternifolia),Cinnamon (Cinnamomum zeylanicum), Cloves (Syzygium aromaticum),lemongrass (Cymbopogon flexuosus), Thyme,( Thymus vulgaris), Eucalyptus (Eucalyptus globulus), Jojoba (Simmondsia chinensis) were tested for their fumigant activity against Callosobruchus maculatus (L.) and Sitophilus oryzae (L.) adults. Percentage mortality increased with increasing concentration of different oils and exposure period. C. zeylanicum and M. alternifolia gave 90.0 % mortality at 8.0 and 16.0 µl /50 ml air, respectively, at exposure period of 24 hour for S. oryzae . C. zeylanicum , M. alternifolia and T. vulgaris essential oils gave 100% mortality at 8.0 , 16.0 and 16.0 µl /50 ml air , respectively, at exposure period of 24 hour for C. maculatus. Both species were found to be highly susceptible to C. zeylanicum whereas the LC95 values were 3.67 and 4.7 µl /50ml air for S. oryzae and C. maculatus, respectively, at exposure period of 72 hour. C. maculatus was more sensitive than S. oryzae to the essential oils of S. aromaticum and E. globulus whereas the LC95 values were 1.032 and 3.66 µl /50ml air, respectively , while the LC95 values to S. aromaticum and E. globulus were 4.07 and 8.73µl /50ml air, respectively , for S. oryzae at the same exposure period.