Spray adulticidal effects of plant oils against house mosquito, Culex pipiens pallens (Diptera: Culicidae)

We examined the adulticidal activity of 34 plant essential oils when they were sprayed on female Culex pipiens pallens adults. At concentrations of 1000 ppm, four oils, namely, cardamom, coriander, rosemary, and sandalwood, had adulticidal activities ranging from 68% to 98% at 1hr after treatment. Insecticidal efficacy decreased with all essential oils at 6 and 24 hr after treatment; however, sandalwood maintained an efficacy rate of over 85%. Sandalwood oil had the highest adulticidal activity with an LC50 value of 445 ppm at 1 hr after treatment. Gc/MS analysis revealed that the major components of sandalwood oil were alpha-santalol (69.4%) and beta-santalol (15.3%). In the insecticidal activity of major monoterpene components of the four oils, a-santalol and beta-santalol proved to have the lowest LC50 values 1, 6, and 24 hr after treatment. When PBO, DEF, TPP and DEM known inhibitors of enzyme-related insecticide resistance promotion, were mixed with each of the four essential oils, a synergistic effect was observed in the mixture of PBO (100 ppm) and sandalwood (500 ppm) up to more than 80%, and the effect was maintained up to 24 hr after treatment. (C) Pesticide Science Society of Japan