Preliminary studies on the effects of Taiwanese ritual smoke on Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae)

Abstract

Smoke from burning plants is a traditional spatial repellent against insects worldwide. Smoke is also commonly used in religious rituals. In Chinese folk religion and Taoism as practiced in Taiwan, Asiatic wormwood leaves, agarwood incense sticks, and joss paper (“ghost money”) are often burned or carried to pray for health or at festivals that overlap with peak mosquito seasons. The possibility exists that some of these rituals became popular due to repellent effects of the smoke reducing the impact of insect-vectored pathogens. The effects of these smokes on the Dengue-vectoring mosquito Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae) was measured following the World Health Organization guidelines for spatial repellency testing. The chemical constituents of the smoke were identified using a solid-phase microextraction fiber for extraction followed by gas chromatography/mass spectrometry. Smoke from wormwood weakly repelled mosquitoes and had some knock-down effects. Smoke from incense showed consistent but weak repellency effects, with no knock-down. Smoke from joss paper had no effect overall, with some mosquitoes seemingly attracted to the flames. While air pollution remains a concern regarding smoky incense, the possibility that mosquito-repelling volatiles can be isolated from the incense and utilized without smoke justifies deeper investigation into the source of these repellent effects.