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We have tested ten essential oils against the cabbage looper,T.ni larvae for contact,residual and fumigant toxicities and feeding deterrent effects.Against third instar T.ni larvae,clove leaf oil (positive control) was the most toxic (LD50 =47.8 μg/larva) via topical application,followed by thyme oil (positive control) (LD50 =52.0 μg/larva),white camphor oil (LD50 =76.0 μg/larva),Litsea pungens oil (LD50 =87.1 μg/larva),and wintergreen oil (LD50 =94.0 μg/larva).Citronella and lemongrass oils were the least active (LD50s =163.4 μg/larva and 167.5 μg/larva respectively) as contact toxins.Thyme oil (LC50 =4.8mg/ml),clove leaf oil (LC50 =6.0 mg/ml),lemongrass oil (LC50 =7.7 mg/ml),cinnamon (LC50 =8.5 mg/ml),and citronella oil (LC50 =10.1 mg/ml) were the most active in a residual bioassay.The remaining five oils showed little or no residual effects.In a fumigation bioassay,L.cubeba oil was the most active (LC50 =16.5 μL/L)followed by wintergreen oil (LC50 =22.2 tL/L),white camphor oil (LC50 =29.7 μL/L),Sabina oil (LC50 =31.2 μL/L) and L.pungens oil (LC50 =39.9 μL/L).Clove leaf oil did not exhibit any fumigant toxicity.Lemongrass oil,citronella oil and cinnamon oil strongly deterred feeding by fourth instar T.ni larvae (DC50s =26.9,33.8 and 39.6 μg/cm2 respectively) in leaf disc choice bioassays.Sabina oil was the least active (DC50 =80.8 μg/cm2).Although,there was a lack of correlation in toxicities between the different bioassays,we found a strong positive correlation between residual toxicity and fumigation toxicity.Based on the responses of T.ni larvae to the oils in different bioassays we can suggest that some of these essential oils exhibit different modes of action.Based on their comparable efficacy with essential oils already used as active ingredients in some commercial insecticides (i.e clove oil and thyme oil),some of these essential oils may have potential as botanical insecticides.