D3009: Repellent efficacy of 21 essential oils from the EPA’s Minimum Risk Pesticides list on yellow fever mosquitoes and deer ticks using three different contact-repellency assays

Active ingredients from the Environmental Protection Agency’s (EPA) Minimum Risk Pesticides list were selected for their potential repellent properties against blood-sucking arthropods. In a previous study, we tested the long-distance repellency of 21 essential oils from this list on the yellow fever mosquito, Aedes aegypti, in a Y-tube olfactometer choice assay. Of the 21 essential oils tested, only cinnamon, peppermint, spearmint, lemongrass, and garlic significantly reduced mosquito attraction to a human host.

In this study, we tested the repellent efficacy of the same 21 essential oils on the yellow fever mosquito, Aedes aegypti, and the deer tick, Ixodes scapularis. To test these active ingredients, we made 10% emulsions of each one and used three different assays that measure contact repellency. We utilized an artificial feeding assay and an arm-in-cage assay to measure repellent efficacy on mosquitoes, and we used a tick arm assay to measure complete protection time from tick crossings. It was revealed that the 21 essential oils vary greatly in their repellent properties. Essential oil emulsions with either peppermint, spearmint, or geranium provided protection against mosquito bites and tick crossings for more than 90 minutes, while emulsions with citronella oil protected for an average of 88 minutes.

We conclude that specific active ingredients from the EPA Minimum Risk Pesticides list provide full protection from mosquito bites and tick crossing for short durations of time.