Spatial repellency effects of Taiwanese plant oils on the biting midge, Forcipomyia taiwana

The biting midge, Forcipomyia taiwana (Shiraki) (Diptera: Ceratopogonidae), can cause severe allergic reactions. It can pass through typical mosquito netting, so repellents are an important control measure against it. This project sought to identify spatial repellents from plants traditionally used by Taiwanese Aboriginal peoples as insect repellents. Fresh plant leaves were collected, frozen, and powdered, and essential oils extracted using hexane then ethyl acetate as solvents. Some commercial oils were also used. The extracts were tested against lab-reared F. taiwana using a Y-tube olfactometer. The composition of the extracts was identified using gas-chromatography mass-spectrometry (GC-MS). Commercial citronella, lavender, and Formosan cypress oils were effective repellents, as were lab-made capillary wormwood and camphor oils. Knockdown was detected in commercial clove leaf, rosemary, common wormwood, and cajuput oils. The oil composition data is the first for many of the Taiwanese plants, many of which contained repellent compounds like caryophyllene, alpha-pinene, and germacrene D. The results agreed with previous studies on the effects of some plants but differed on others, possibly due differences in plant chemotype, extraction method, and oil concentrations.

Automated summary

This study aimed to find spatial repellents from plants traditionally used by Taiwanese Aboriginal peoples to control the biting midge, Forcipomyia taiwana. Plant leaves were collected, frozen, and powdered. Essential oils were extracted using hexane and ethyl acetate solvents and tested against F. taiwana. The composition of the extracts was identified using GC-MS. Commercial citronella, lavender, and Formosan cypress oils were effective repellents, as were lab-made capillary wormwood and camphor oils. The oil composition data provided new insights into the repellent compounds found in Taiwanese plants.