The use of aromatic plants to deter insects offers a natural method to manage common pests like mosquitoes and flies. Plants produce volatile organic compounds (VOCs) as a self-defense mechanism against herbivores. These strong scents work by overwhelming or confusing the insects’ highly sensitive chemoreceptors, masking the attractant smells of a host or food source. Strategically incorporating these fragrant botanicals into outdoor and indoor spaces creates a localized zone of deterrence.
Plants That Specifically Deter Mosquitoes
Mosquitoes are particularly sensitive to terpenoids, the active chemical compounds found in many fragrant herbs and grasses. Citronella grass, a well-known repellent, contains citronellal, citronellol, and myrcene, which inhibit mosquito host-seeking activity by disrupting their sense of smell. Catnip is another highly effective repellent plant, containing the compound nepetalactone. Some studies suggest nepetalactone is more potent than the synthetic repellent DEET against certain mosquito species, interfering with the insect’s ability to detect carbon dioxide and lactic acid.
Other Mosquito Deterrents
Lemon Balm, a member of the mint family, contains citronellal and geraniol, contributing to its strong, lemon-like scent that mosquitoes actively avoid. Lavender deters mosquitoes due to high concentrations of linalool and camphor, which disrupt the neurological systems of flying insects.
Plants That Specifically Deter Flies
Flies are deterred by volatile compounds, often preferring plants with an intensely spicy or herbaceous aroma. Basil is an effective fly deterrent, owing its properties primarily to essential oils such as methyl chavicol (estragole), eugenol, and linalool. These compounds provide a strong, confusing scent that prevents flies from locating food and breeding sites. Mint varieties, such as peppermint, contain high levels of menthone and menthol, which are disagreeable to flies and mask the odors of potential food sources.
Bay Leaf, sourced from the Laurus nobilis tree, is noted for its repellent qualities against flies. The leaves contain cineole, which produces a strong, sharp aroma that acts as a sensory irritant to flying pests. Placing these plants in areas where food preparation or consumption occurs can help maintain a fly-free zone.
Maximizing Deterrence Through Placement and Use
The simple presence of an aromatic plant often provides only a localized, low-level repellent effect because volatile compounds are not rapidly released into the air. To maximize deterrence, the foliage must be mechanically activated, such as by brushing against the leaves or lightly crushing them. This action ruptures the oil glands within the plant tissue, releasing a plume of concentrated VOCs into the immediate surrounding area.
Placing plants in high-traffic areas, like near doorways or beside seating areas, increases the chance of accidental activation and maximizes the repellent zone. Growing these plants in containers provides flexibility for strategic placement and allows them to be moved indoors during the off-season. Regularly pruning the plants also encourages new growth, which tends to be richer in insect-repelling essential oils.
Safety Considerations and Plant Toxicity
While these plants are natural deterrents, their safety must be considered, particularly regarding children and household pets. Many common insect-repelling plants contain compounds that are toxic if ingested in large quantities. For example, Citronella grass is listed as toxic to cats and dogs, and ingestion can lead to digestive upset or hypothermia. Lavender and basil are generally safe for humans and non-toxic to dogs, but lavender essential oils can cause vomiting if ingested by cats. Pet owners should exercise caution and place all deterrent plants in areas where they cannot be easily chewed or consumed.