The objectives of the present study were to determine the lethal and sublethal effects of basil, Ocimum basilicum, fenugreek, Trigonella foenum-graecum and garlic, Allium sativum essential oils (EOs) against Callosobruchus maculatus and Tyrophagus putrescentiae. In view of the importance of using predators and parasitoids in IPM programs for the biological control of C. maculatus and T. putrescentiae, the impact of lethal and sublethal concentrations of EOs on the Hymenoptera parasitoid, Anisopteromalus calandrae and the predator mite, Cheyletus malaccensis were evaluated, in order to contribute to IPM programs that use both EOs and parasitoid and predator releases. Data obtained demonstrated that mortality of C. maculatus on cowpea seeds treated with sub lethal concentrations equivalent to 1/5 LC50 of A. sativum EO was higher than O. basilicum EO and T. foenum-graecum EO 5 days post exposure. A similar trend was observed for T. putrescentiae. All EOs at sublethal concentrations were highly detrimental to both A. calandrae and C. malaccansis. A. sativum and O. basilicum were the least compatible with A. calandrae, as they caused 83.33±3.33 and 76.673.33% mortality 5 days post exposure, respectively. The level of toxicity observed in the effect of sublethal concentration of EOs on A. calandrae was also similar in case of the predator mite, C. malaccansis. A. sativum EO still induced the highest mortality to C. malaccensis (80.05.77%) followed by O. basilicum (73.33±3.33%) and T. foenum-graecum (66.60±6.66%) EOs, 5 days post treatment. Based on lethal and sublethal direct exposure study, it could be concluded that all EOs evaluated were generally highly detrimental and non selective to both A. calandrae and C. malaccansis and would be incompatible with biological control of C. maculatus and T. putrescentiae.
Key words: essential oils, sublethal effect, C. maculatus, T. putrescentiae
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