What Insects Are Repelled By Citronella Oil?
Citronella oil is an essential oil derived from lemongrass plants in the Cymbopogon genus. It has a strong, distinct lemony aroma and has been used for decades as a natural insect repellent. When applied topically or burned in lamps, candles or torches, citronella oil helps repel insects like mosquitoes, ticks, fleas, flies, ants, bees, cockroaches and more. The main active ingredient that provides the repellent effect is citronellal.
In this article, we will provide an overview of the key insects that citronella oil is known to effectively repel through scientific research and anecdotal evidence. We will explore how it works to deter insects and outline the best ways to use citronella oil safely and effectively as an alternative to harsh chemical repellents.
Mosquitoes
Citronella oil is one of the most popular natural insect repellents, especially against mosquitoes. Studies have shown that citronella oil repels and drives away several species of mosquitoes including the common house mosquito Culex pipiens, the southern house mosquito Culex quinquefasciatus, and the yellow fever mosquito Aedes aegypti (1). Citronella oil is registered as an insect repellent by the Environmental Protection Agency and approved for topical use by the Food and Drug Administration (2).
Citronella oil contains citronellal as its major component, which interferes with mosquitoes’ sense of smell. Mosquitoes locate hosts through scent detection of carbon dioxide and other attractants like lactic acid. Citronella oil masks these attractants, making the host essentially “invisible” to mosquitoes (1). This disruption in scent detection makes it difficult for mosquitoes to find hosts to bite.
While citronella oil provides short-term protection, it must be reapplied frequently as the oil evaporates. Mosquito protection times range from 30 minutes to 2 hours based on the concentration of citronella (3). Oils with higher concentrations of citronellal provide longer protection. Products like lotions and sprays that allow the oil to remain on the skin also extend the duration of repellency.
(1) http://npic.orst.edu/factsheets/citronellagen.html
(2) http://npic.orst.edu/factsheets/citronellagen.html
(3) http://npic.orst.edu/factsheets/citronellagen.html
Ticks
Citronella oil has been shown to be effective at repelling ticks, especially when combined with thyme oil. One study found that a mixture of 10-15 drops of citronella oil plus 5 drops of thyme oil diluted in water and sprayed on clothing provided 98% repellency against ticks for up to 2 hours [1]. Citronella oil’s main active ingredient, citronellal, is thought to mask the carbon dioxide released by hosts, making it harder for ticks to locate and latch on. This repellent effect works against common tick species like deer ticks, dog ticks, and lone star ticks.
Some research also indicates that citronella oil may have insecticidal effects, potentially killing or damaging ticks on contact [2]. However, more studies are still needed to fully evaluate citronella’s acaricidal properties against ticks.
Fleas
Citronella oil has been shown to be an effective flea repellent, especially against the common cat flea (Ctenocephalides felis) and dog flea (Ctenocephalides canis). According to research, citronella oil contains compounds like geraniol and citronellol that are toxic to fleas and can kill adults as well as eggs and larvae[1]. When used properly in sprays, diffusers, or on pet collars, citronella oil can repel fleas for up to 24 hours. It works by masking scents that attract fleas to hosts and interfering with flea nerves and mobility.
Studies have found that higher concentrations of citronella oil tend to be more effective against fleas. A 5% citronella spray used daily can eliminate flea infestations over 2-3 weeks. Combining citronella oil with other natural repellents like geranium, peppermint, or lemongrass oil can also boost effectiveness against fleas. Overall, citronella oil is considered a safe, natural alternative to harsh chemical flea treatments for use on pets and in the home when properly diluted[2].
Flies
Citronella oil has been shown to be an effective repellent against various fly species. According to studies, citronella oil contains compounds like geraniol, citronellol, citronellal, and geranyl acetate that have insecticidal and repellent properties against flies.1 When diffused or sprayed in the air, the scent masks attractants that draw flies in, making it harder for them to locate and land on treated areas and humans.
Citronella oil has been found effective against common houseflies, stable flies, horn flies, and eye gnats or face flies. One study showed that 5% citronella oil was able to repel stable flies for up to 4 hours. It’s also been shown to provide some repellency against the common housefly, preventing around half from entering treated areas for 1-2 hours.2 The exact mechanisms of how citronella oil repels each fly species requires more research. However, it likely functions by masking attractants, interfering with fly olfactory receptors, and acting as a spatial repellent.
Ants
Citronella oil is an effective natural repellent against many ant species. Studies have shown that citronella oil contains compounds like geraniol, citronellol, and citronellal that deter ants 1. When applied topically or diffused in areas where ants are problematic, citronella oil helps repel ants and prevent infestations.
Research indicates citronella oil is particularly effective against red imported fire ants, Argentine ants, pharaoh ants, pavement ants, and odorous house ants. The strong scent confuses the ants’ scent trail and disrupts their ability to follow pheromone trails back to the nest 2. This helps break up ant colonies and repel them from homes and gardens.
Citronella oil can be used to make homemade ant sprays by combining it with water and spraying it directly on ant trails and around doors, windows, and other ant entry points. Diffusing citronella oil indoors is also an effective deterrent. Using citronella oil is an eco-friendly and non-toxic way to repel ants without harsh chemicals.
Bees
Citronella oil is generally an effective repellent against bees, including honey bees and bumble bees. The main compounds in citronella oil that bees dislike are citronellal, citronellol, and geraniol.1 These compounds overwhelm the bees’ sense of smell, making it harder for them to locate flowers or be attracted to an area.2
When bees detect the strong scent of citronella oil, they tend to avoid and move away from the area where it is present. Citronella oil can be used in candles, torches, or essential oil diffusers to repel bees from patios, gardens, or other outdoor spaces.3 It provides a simple, natural way to discourage bees without harming them.
Cockroaches
Citronella oil has shown some effectiveness in repelling cockroaches, especially the German cockroach (Blattella germanica) and American cockroach (Periplaneta americana). When mixed with a small amount of alcohol, citronella oil can deter and drive away cockroaches through its strong aroma. The exact mechanism is unclear, but it’s believed the scent overwhelms the cockroach’s chemical senses, making them avoid areas treated with citronella.
One study found that a 1% citronella oil solution repelled up to 80% of cockroaches in lab tests. Higher concentrations like 5% performed even better. The repellent effects last for several hours after application. Citronella is considered a safe, natural option compared to harsh chemical pesticides. It does not kill cockroaches, but acts as an effective deterrent. The strong citronella scent makes an area inhospitable and pushes cockroaches away to other locations.
While promising, citronella oil should be used carefully around cockroaches. Avoid contaminating food surfaces, and spot test on delicate materials first. Monitor for any cockroach aggregation or nesting sites, and treat those areas directly for best results. Citronella oil cockroach sprays and vapors can provide immediate repellency, while infused devices like candles or diffusers provide gradual, sustained repellency over time. Overall, citronella oil is a helpful addition to an integrated pest management plan, but not a standalone solution for cockroach elimination.
Sources:
https://www.ecoguardpestmanagement.com/pest-resources/cockroach-repellent
https://www.housedigest.com/1476559/citronella-oil-repel-roaches-pest-control/
Other Insects
Citronella oil has some repellent effects against insects besides mosquitoes, ticks, fleas, flies, ants, bees, and cockroaches. According to the US EPA’s Pesticides – Fact Sheet for Oil of Citronella, citronella oil is registered as both an insect repellent and an animal repellent, suggesting it has broad efficacy against insects and arthropods.
One study found that citronella oil repelled up to 92% of house spiders after 2 hours when applied to cardboard panels in a test chamber. The repellent effects declined over time but remained over 50% effective after 24 hours (source).
Citronella oil has also shown repellent activity against bed bugs. In lab studies, direct application of citronella oil provided over 80% repellency against bed bugs for 2-4 hours after application (source).
Overall, citronella oil appears to have broad repellent effects against many insects, spiders, and arthropods beyond just mosquitoes. However, more research is still needed to fully understand its efficacy for different species.
Conclusion
In summary, the key insects that citronella oil has been shown to effectively repel include mosquitoes, ticks, fleas, and flies. Of these, citronella oil seems most effective at repelling mosquitoes when applied directly to the skin or when used in products like candles or torches.
Some of the most effective uses of citronella oil as an insect repellent are:
- Applying it directly to the skin as part of a repellent lotion, spray, or oil
- Using it in outdoor candles or torches placed near areas where you want to repel insects
- Adding a few drops to a diffuser or evaporator inside to repel indoor flies and mosquitoes
- Spraying it around the perimeter of an outdoor gathering area
- Using it in a collar or spray for dogs and cats to repel fleas and ticks
While citronella oil is not as powerful or long-lasting as DEET and some other synthetic insect repellents, it can still be an effective, plant-based option for repelling mosquitoes, ticks, fleas, and flies in the right circumstances.
