Can plants really repel mosquitoes?
Story and Photos by Sue Hughes
It’s summer, and that means war … on mosquitos! In 2014 Bill Gates called the mosquito “The Deadliest Animal in the World.” They carry a host of debilitating and often fatal diseases. Yes, we can douse ourselves with chemicals, light some incense, or plug in the bug zapper … but rumor has it that plants can also keep mosquitos at bay. [Editor’s Note: Mosquitos are vectors of several potentially life-threatening diseases, and protecting yourself is perhaps more important now than ever before. For more information, visit wwwnc.cdc.gov/travel/page/avoid-bug-bites.]
The essential oils in some plants and flowers have been said to repel mosquitos, while you should not rely on plants alone to protect you from mosquito bites, you may want to include a few in your landscape or garden.
Lemon grass (Cymbopogon citratus)
Citronella oil, the active ingredient in many mosquito repellents, is extracted from various species of this perennial clumping grass.
Surely a plant that contains citronella repels mosquitos, right? Yes and no: It’s the oil that does the repelling, not the plant, so rubbing the crushed leaves directly on your skin is the most effective way to use the plant as a repellent.
Lemongrass is nice addition to any landscape, and its aromatic oil is released whenever something brushes against it. It grows 2-4 feet tall, prefers full sun, and is a fast grower.
Mosquito plant a.k.a. Citronella geranium (Pelargonium ‘Van Leenii’)
One would think that any plant with mosquito in its name would work as a repellent—but alas, no. Despite that marketers sell this citronella-scented geranium as a mosquito-repellent, one published study reported, “There was no significant difference between citrosa-treated and nontreated subjects.” (1)
So, it may not repel mosquitoes, but it does make a great container plant. It grows large and bushy with thick foliage of lacy, medium-green leaves and produces a few pink-purple blossoms during the season.
It can reach 1-2 feet tall and wide. In midsummer, prune back its woody branches to keep it nicely shaped and cut back the main central stem to promote fullness and encourage flowering.
Lavender (Lavendula spp.)
Most of us love the scent of lavender. Its oil, extracted from the plant’s tiny blue-violet flowers, works as an effective and natural mosquito repellent when applied directly on your skin. Contrary to synthetic chemical repellants, lavender oil nourishes your skin with no unpleasant side effects and studies have shown that lavender oil does repel some insects.
Rosemary (Rosmarinus spp.)
Rosemary does triple duty as an herb, aromatic landscape filler, and pest repellant. Herb gardeners love to use snippets of rosemary in meat, soup, and egg dishes, while its silvery green foliage and blue, pink, or white blooms make an attractive addition to a container or flowerbed.
But while we find the oil of this shrub heavenly, mosquitos find it disgusting – so do flies and cabbage moths. The oil of R. officinalis has been proven to not only repel mosquitoes, it also kills mosquito eggs. (3)
This evergreen perennial shrub thrives in full sun and in well-drained soil, and tolerates poor, sandy, or gravelly soils.
Catnip (Nepeta spp.)
Generally associated with cat toys and snacks, a 2001 American Chemical Society study found the essential oil in catnip to be about 10 times more effective than DEET at repelling mosquitoes when applied directly on your skin. Results showed that this compound exhibits both irritant and repellent actions. While generally safe, some experience minor skin irritation when they come in direct contact with catnip oil.
But another study concluded “that catnip oil and nepetalactone isomers are significantly less effective than deet or SS220 in deterring the biting of Ae. aegypti.” (4)
Catnip thrives in full sun to partial shade in well-drained soil. To promote bushier growth, cut back the tops of catnip plants when they reach about 12 inches long.
Regardless of whether you grow these plants to keep the bugs away or just because they look good, there is promising research out there proving that plant-based repellents do work. A study published in Malaria Journal, “Plant-based insect repellents: a review of their efficacy, development and testing,” concluded: “The field of plant-based repellents is moving forward as consumers demand means of protection from arthropod bites that are safe, pleasant to use and environmentally sustainable.” (5)
One published study concluded “The various phytochemicals like Citronellal, Azadirachtin, linalool and p-Menthane- 3,8-diol obtained from citronella plant, neem, lavender and mentha plant respectively are found to responsible for the mosquito repellant activity. So this review can certainly bring awareness to public to keep away from mosquitoes in a natural way.” (2)
(1) Arthur, O., and J. Maciarello. “Essential oil analysis and field evaluation of the citrosa plant “Pelargonium citrosum” as a repellent against populations of Aedes mosquitoes.” Journal of the American Mosquito Control Association12.1 (1996): 69-74.
(2) Geetha, R. V., and ANITHA ROY. “Essential Oil Repellents-A short Review.” International Journal of Drug Development and Research (2014).
(3) Prajapati, Veena, A. K. Tripathi, K. K. Aggarwal, and S. P. S. Khanuja. “Insecticidal, repellent and oviposition-deterrent activity of selected essential oils against Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus.” Bioresource technology 96, no. 16 (2005): 1749-1757.
(4) Chauhan, Kamlesh R., Jerome A. Klun, Mustapha Debboun, and Matthew Kramer. “Feeding deterrent effects of catnip oil components compared with two synthetic amides against Aedes aegypti.” Journal of medical entomology 42, no. 4 (2005): 643-646.
(5) Maia, Marta Ferreira, and Sarah J. Moore. “Plant-based insect repellents: a review of their efficacy, development and testing.” Malaria Journal 10, no. 1 (2011): S11.