Lemongrass, derived from various Cymbopogon species, is a perennial grass recognized for its potent, fresh citrus aroma. This distinctive fragrance is the basis of its traditional use as a natural defense against biting insects. The essential oil is extracted from the plant’s leaves and stems to create a botanical repellent. This article details the specific compounds that make lemongrass a successful deterrent and identifies the insects it is known to repel.
The Primary Repellent Compounds
The insect-repelling action of lemongrass essential oil stems from a complex mix of naturally occurring organic molecules called terpenes. The most abundant compound is citral, an isomeric blend of two aldehydes: geranial (citral A) and neral (citral B). These two structures typically make up 65% to 85% of the oil’s composition and are the primary biologically active agents.
The oil also contains smaller amounts of other repellent molecules, including geraniol and citronellol. These volatile compounds disrupt the sensory systems of insects. They are detected by the insects’ antennal olfactory receptor cells, which are used to locate hosts by detecting carbon dioxide and other attractants. By flooding the air with this strong scent, lemongrass effectively masks the signals that attract pests, confusing their navigation.
Key Insects Repelled by Lemongrass
Mosquitoes
Lemongrass is most recognized for its effectiveness against mosquitoes, which are vectors for various diseases. Studies confirm its repellent and insecticidal activity against multiple species, including the disease-transmitting Aedes aegypti, Anopheles dirus, and Culex quinquefasciatus. The oil’s strong aroma creates an area of avoidance, making it difficult for female mosquitoes to locate a blood meal.
In controlled laboratory environments, a 10% concentration of lemongrass essential oil demonstrated potent toxicity. This resulted in the death of 100% of these three mosquito species within 24 hours of exposure, suggesting the oil’s action includes a direct insecticidal effect beyond simple deterrence.
Biting Flies and Ticks
The essential oil is also highly effective at repelling various biting and nuisance flies. It deters stable flies (Stomoxys calcitrans) and common house flies (Musca domestica). In one experiment, stable flies spent significantly more time in an untreated zone than in an area treated with lemongrass oil, and none fed on treated pads.
Recent research has highlighted its potential against ticks, particularly blacklegged ticks. The oil contains compounds like geraniol and citral that weaken the tick’s ability to detect human scent markers, such as butyric acid. This sensory impairment reduces the tick’s capacity to find a host, potentially lowering the risk of bites and disease transmission.
Other Pests
The repellent properties of lemongrass extend to a range of other insect pests. It deters the brown marmorated stink bug (Halyomorpha halys), with over 95% of insects avoiding treated traps. Lemongrass oil also shows strong repellency against vespid wasps, including yellowjackets and paper wasps.
The oil’s citral content acts as a potent control agent for subterranean termites (Coptotermes formosanus). Treated sand proved 100% effective in laboratory conditions, confirming the versatility of lemongrass as a natural pest control agent.
Practical Application Methods
Lemongrass is utilized in several forms for insect control, from horticultural use to commercial products. Growing the live plant in the garden, particularly near seating areas, offers some localized perimeter protection. To maximize the effect, the leaves must be crushed to release the volatile essential oils, as the intact plant alone may not release enough scent to be an effective deterrent.
The most common application uses the concentrated essential oil for personal protection. For topical use, the oil must be diluted in a carrier oil such as jojoba or coconut oil before application. A common dilution ratio is 3 to 5 drops of lemongrass essential oil per tablespoon of carrier oil.
For area protection, the oil can be added to diffusers to disperse the repellent scent indoors, deterring gnats and mosquitoes. Homemade sprays are also popular, created by mixing the essential oil with water and an emulsifier like witch hazel or vodka. Commercially, the oil is infused into candles, torches, and incense sticks, which are burned outdoors to create a localized, aromatic barrier.