Screening of larvicidal activity of 53 essential oils and their synergistic effect for the improvement of deltamethrin efficacy against Aedes albopictus

Although the extensive use of synthetic insecticides to control mosquito vectors have gained significant success, meanwhile resulted in various problems, such as increase in insecticide-resistant mosquitoes, environmental pollution, and health threat to human beings. Hence, there is an urgent need for alternative insecticides and effective synergists to combine with existing insecticides, which are safe to public health and environment. In this work, the larvicidal activity of 53 commercial essential oils (EOs) and their synergistic effect with deltamethrin against Aedes albopictus adults were screened, then the main constituents of active EOs were analyzed by GC-MS. The most potent EOs against the larvae are from Foeniculum vulgare (fennel), Thymus vulgaris (thyme), Citrus medica (lime), and Camellia sinensis (green tea) with LC50 values of 27.5, 31.6, 51.3, 53.5 ppm, respectively. The most efficient EOs enhancing the efficacy of deltamethrin are C. sinensis (green tea), the co-toxic factor is 316.67, which is more than the positive control PBO (co-toxic factor = 283.35). It suggests that there is significant potential of natural EOs in the application of mosquito control as larvicides or synergists for enhancing efficacy of current adulticides.