Lemon Verbena (Aloysia citrodora) is a flowering shrub celebrated for its intense, sweet lemon fragrance. Originating in South America, the plant has long been popular in culinary applications, perfumes, and potpourri. Its powerful aroma led to its traditional use as a natural household repellent. Modern investigation now focuses on evaluating the scientific validity and practical effectiveness of the plant as an insect deterrent.
Active Compounds Responsible for Repellency
The insect-repelling properties of Lemon Verbena are concentrated in its essential oil, a complex mixture of volatile organic compounds. The primary active components are monoterpenes, which give the plant its characteristic scent and ability to deter pests. These monoterpenes are dominated by Citral, a compound that is a mixture of two isomeric aldehydes: Geranial and Neral.
Geranial and Neral often constitute a significant portion of the oil, sometimes exceeding 47% of the total essential oil composition. Other notable compounds, including Limonene and Linalool, also contribute to the deterrent effect. These volatile molecules interfere with the olfactory receptors of insects, masking attractive host scents like carbon dioxide and body odor. By disrupting the insect’s ability to locate its target, the plant’s scent acts as a barrier that causes pests to avoid the area.
Specific Pests Lemon Verbena Targets
Lemon Verbena is effective against a range of common flying and crawling pests, largely due to the high concentration of citral and other terpenoids in its essential oil. The plant is widely recognized for its ability to repel mosquitoes, a common focus of natural repellent research. Lemon-scented herbs are generally useful for repelling both mosquitoes and flies, making the plant a dual-purpose deterrent for outdoor areas.
Scientific studies have demonstrated fumigant toxicity against stored-product insects, such as the cowpea weevil (Callosobruchus maculatus) and the confused flour beetle (Tribolium confusum). Anecdotal and traditional usage also points to its effectiveness against midges, gnats, and garden pests like whiteflies and aphids. The deterrent effect stems from its potent volatile compounds, which are noxious to insects that rely on scent for navigation and host location.
Practical Methods for Use
There are several simple methods to use Lemon Verbena as a repellent and release the active compounds. Growing the plant in pots or in the ground around outdoor seating areas serves as a passive perimeter barrier. The natural scent released from the leaves helps to keep flying insects out of the immediate vicinity.
For more direct, temporary protection, the fresh leaves can be crushed or rubbed directly onto exposed skin. This action immediately releases the concentrated essential oil, providing a short period of localized repellency against mosquitoes. A more lasting application involves creating a simple infusion or oil-based spray by steeping the leaves in a carrier oil like olive or almond oil, or by making a tincture with alcohol or witch hazel. Combining the plant material with a carrier agent helps distribute the active molecules and keeps the repellent on the skin for a longer duration.
Safety Considerations and Potential Drawbacks
While Lemon Verbena is a natural option, using its concentrated forms requires awareness of potential negative effects. Applying the essential oil directly to the skin, or using highly concentrated homemade preparations, may cause skin sensitivity, known as contact dermatitis, in some individuals. Some users have reported an itchy rash following topical application.
For households with pets, it is important to note that many essential oils, including those from Lemon Verbena, can be harmful if ingested, especially by smaller animals. A limitation of natural repellents is their shorter duration of effectiveness compared to synthetic products like DEET. The volatile nature of the active compounds means they evaporate quickly, necessitating frequent reapplication for continuous protection.