The use of certain plants to manage common household pests like flies is a popular natural alternative to chemical insecticides. Specific botanicals produce compounds that flies find highly offensive, encouraging them to seek an environment elsewhere.
How Plants Naturally Repel Insects
This repellent action relies on the plant’s natural defense system, which involves the production of Volatile Organic Compounds (VOCs). These airborne chemicals, often referred to as essential oils, are synthesized and stored within the plant’s tissues. The molecules easily evaporate into the surrounding air, creating a scent barrier.
For a fly, these VOCs act as powerful deterrents by disrupting its highly sensitive olfactory system. The chemicals interfere with the insect’s smell receptors, making it difficult for the fly to locate sources of food or potential mates. This confusion and sensory overload prevent the insect from settling in the area.
Essential Plants That Deter Flies
Six plant options are recognized for their effectiveness in deterring flies. The Citronella plant, a type of aromatic grass, contains a blend of compounds including citronellal, citronellol, and geraniol. The combined effect of these volatile alcohols and aldehydes creates the strong, lemony scent flies actively avoid.
Basil is a culinary herb that also serves a dual purpose as a fly repellent, primarily through its constituents estragole and linalool. Different varieties of basil can also contain eugenol, all of which contribute to the herb’s potent aroma that houseflies find disagreeable. Planting basil near doorways or kitchen windows can create a localized zone of deterrence.
Lavender’s pleasant, floral scent, which is largely attributed to the monoterpenes linalool and linalyl acetate, is a significant turn-off for flies. These compounds work to disrupt the fly’s nervous system, leading to avoidance behavior. The plant is particularly effective when placed in areas with good airflow to disperse the fragrance.
Mint, especially peppermint or spearmint varieties, is highly effective because of its main active compound, menthol. Menthol and its related ketone, menthone, produce a sharp, intense aroma that flies instinctively avoid. Due to mint’s vigorous growth habit, it is often best contained in pots to manage its spread while maximizing its fly-repelling presence.
Marigolds are flowering plants that release a distinct, pungent odor that is repellent to numerous insects. The chemical agents responsible for this effect are primarily thiophenes, and specifically alpha-terthienyl, which is found in the roots and foliage. These compounds create a boundary that many flying pests are reluctant to cross.
The aromatic Bay Laurel, often grown as a small tree or shrub, contains oils rich in eucalyptol, also known as 1,8-cineole. Eucalyptol, along with linalool, gives the bay leaf its strong, sharp scent that is known to repel flies and other pantry pests. Dried bay leaves are sometimes placed directly into cupboards to use this repellent property indoors.
Maximizing the Repellent Effect
For these plants to be most effective, strategic placement is crucial. The concentration of the volatile compounds must be high enough in the air to disorient the flies’ navigation. Placing potted herbs near entrance points, such as on patios, windowsills, and decks, creates a protective perimeter.
For maximum release of the aromatic compounds, physically disturbing the plants can be beneficial. Brushing against the leaves, gently crushing a few sprigs, or pruning the plant releases a higher concentration of the stored oils into the immediate atmosphere. Live, actively growing plants should be maintained and pruned regularly to encourage new growth, which often contains the highest potency of repellent oils.
The size of the plant also correlates with its effectiveness, as larger plants have more surface area to release VOCs. Utilizing cut bundles of strongly scented herbs and placing them in bowls inside, or using the fresh leaves as a temporary table centerpiece, can provide a burst of natural repellent when needed most. However, this method requires frequent replacement to keep the aroma potent, as the volatile oils dissipate quickly once the leaves are cut.