Abstract

Repellency and fumigant toxicity of clove (Syzygium aromaticum) and sesame (Sesamum indicum) oils were investigated against American cockroach (Periplaneta americana (L.) in the laboratory of the Department of Biological Sciences, Faculty of Science, King Abdulaziz University, Jeddah Province, Saudi Arabia at 25 ± 3°C and 75 ± 5% relative humidity. Both clove and sesame oils showed variable percentages of repellency according to concentrations, exposure periods and stages. Clove oil exhibited strong repellent activity than sesame oil. First nymph was more sensitive than the fourth one followed by adults. After 48 h of exposure, complete repellency (100%) was recorded against first nymph at concentration of 2% for clove oil and 6% for sesame oil. Same result was obtained against fourth nymph at concentration of 10% of sesame oil after 48 h. While clove oil completely repelled all fourth nymphs after 24 h at concentration of 8%. For adult stage, the greatest repellency percentages were recorded by clove oil (90.00 ± 5.77%) and sesame oil (83.33 ± 3.33%) after 48 h at a concentration of 10%. Regarding the fumigant toxicity, clove oil provided highly significant effects against nymphs and adults of P. americana after 24 and 48 h, respectively. Complete mortality (100%) was recorded at a concentration of 7.5 µl/L of air for first nymph, 10 µl for fourth one and 17.5 µl for adults after 48 h of fumigation. First nymph was the most sensitive to clove oil by LC₅₀ value 1.06 µl followed by 3.12 µl for fourth nymph and 8.20 µl for adults. The fumigant tests showed that sesame oil did not exhibit toxicity against P. americana at concentrations range of 5 to 20 µl/L of air. In conclusion, both clove and sesame oils can be used as repellent botanical insecticides, but only clove oil can be used as fumigant agent against P. americanabecause sesame oil gave no effect at tested concentrations.

Key words: Sesame oil, clove oil, American cockroach, repellency, fumigant toxicity.