Cedar wood is known for its distinctive aroma and ability to deter pests. Historically, cedar chests and closets protected clothing and other items from insect damage. This natural property stems from the underlying science that makes it an effective bug repellent.
The Repelling Chemicals in Cedar
Cedar’s insect-repelling qualities, especially in Eastern Red Cedar (Juniperus virginiana), come from naturally occurring volatile organic compounds (VOCs) within its wood. These aromatic oils evaporate into the air, creating cedar’s characteristic scent. Key VOCs include cedrol, cedrene, and thujone.
Cedrol is a sesquiterpene alcohol contributing to cedar’s insect-repellent properties. Cedrene, another sesquiterpene, also deters insects. Thujone, more prominent in Western Red Cedar, is known for its toxic effects on many insects. Cedar trees produce these compounds as a natural defense mechanism against insects, fungi, and other organisms.
How Cedar’s Compounds Deter Pests
The volatile organic compounds released by cedar wood deter insects through several mechanisms. The strong, pungent scent, primarily from cedrol and cedrene, interferes with insects’ sensory systems. This disruption can mask the pheromones insects use to locate mates, food sources, and egg-laying sites, disorienting them.
For pests like clothes moths, cedar oil vapors can directly impact their development. At higher concentrations, compounds like cedrol are toxic to insect larvae and eggs, inhibiting hatching and causing mortality. Cedar’s oils can also interfere with the chemical balance within insects’ bodies, cause dehydration by leaching moisture from their exoskeletons, or irritate their respiratory systems. This combination of sensory disruption, direct toxicity, and physiological interference makes cedar an effective natural deterrent against a range of pests.
Real-World Effectiveness and Limitations
Cedar wood is effective against various household pests, including clothes moths, carpet beetles, silverfish, termites, cockroaches, ants, fleas, ticks, and mosquitoes. Studies show that even low concentrations of cedar oil can kill moth larvae and prevent egg hatching, while cedar chips can reduce adult moth lifespan.
Cedar’s repellent properties have limitations. Its effectiveness diminishes over time as volatile oils evaporate from the wood. Older cedar products, like antique cedar chests, may be less effective than newer ones unless refreshed. Factors such as oil concentration, ventilation, and product age influence its repellent strength and duration. To maintain potency, cedar wood products often need refreshing by lightly sanding the surface or applying cedar oil; under ideal conditions, cedar can ward off bugs for up to six months, though harsh elements reduce this timeframe.
Safe Application and Important Considerations
Using cedar products for bug repulsion is a safe, natural alternative to chemical pesticides. The Environmental Protection Agency (EPA) recognizes cedarwood oil as a minimum risk pesticide due to its low mammalian toxicity and non-toxic mode of action. This means it poses minimal risk to public health or the environment when used as directed.
Some considerations are important for safe use. While the strong scent is usually pleasant, sensitive individuals may experience allergic reactions, particularly to cedar dust, which can cause skin allergies or respiratory issues like asthma. Proper ventilation is advisable when using cedar products in enclosed spaces, such as closets or chests, to dissipate the strong aroma and minimize irritation. Although natural, cedar is a chemical substance and should be used as intended, avoiding direct ingestion or excessive exposure.