Cedar chips are a popular, natural option for homeowners seeking a less chemical-intensive approach to pest management. They are typically derived from aromatic species like Eastern Red Cedar or Western Red Cedar. The belief that these wood products repel insects stems from their distinct, pleasant aroma, making them a safe, biodegradable alternative to synthetic pesticides. Understanding whether cedar chips are an effective insect repellent requires examining the science behind their scent and how it interacts with various pests.
What Makes Cedar an Insect Repellent
Cedar’s ability to deter certain insects is due to the volatile organic compounds (VOCs) stored within its wood oil. These aromatic oils contain compounds like cedrol and thujone, which are continuously and slowly released into the surrounding air. Cedrol, a sesquiterpene alcohol, vaporizes at room temperature, creating the characteristic scent of cedar.
These natural compounds interfere with an insect’s sensory mechanisms, particularly their olfactory system. The strong, woody odor acts as a natural fumigant or masking agent that disorients the pests. This disruption blocks the insects’ ability to detect pheromones, which they use for navigating, mating, and locating food sources. The repellent action is a sensory overload that makes the area unappealing or impossible for the insects to inhabit normally.
Insects That Cedar Effectively Repels
Cedar chips are most effective against insects that target stored fabrics, such as clothes moths and carpet beetles. The high concentration of cedrol vapor in confined spaces, like chests, drawers, or closets, is often sufficient to deter or even kill the larvae of these pests. Studies confirm that Eastern Red Cedar wood can significantly deter black carpet beetles, making this one of the most reliable uses of cedar products.
Effectiveness against outdoor and general household pests is more variable, depending on the form of cedar used and the concentration of its oils. Cedar is commonly used to repel fleas, ticks, and ants; some research indicates that the cedrol in cedarwood oil shows strong effectiveness against tick nymphs. The chips or granules can also deter cockroaches, mites, and chiggers by disrupting their pheromone pathways. However, for flying insects like mosquitoes in open-air environments, the effect is limited because the VOCs dissipate too quickly to maintain the necessary concentration.
Application Methods for Cedar Chips
The most effective use of cedar chips is in enclosed areas to maximize the concentration of the volatile oils. Placing cedar chips, balls, or sachets in closets, drawers, and storage bins is ideal for protecting clothing from moths and carpet beetles. For this application, the chips should be placed strategically among the stored items to ensure the scent permeates the entire space.
In outdoor settings, cedar chips are frequently used as a mulch in garden beds and around the perimeter of homes. Spreading the chips or granules in a layer around the foundation or along fences establishes a passive barrier against crawling insects like ants, roaches, and termites. Using cedar chips in pet bedding can also help deter fleas and ticks from the animal’s resting area. For consistent outdoor repellency, it is recommended to reapply the granules or chips every four to six weeks, or after heavy rain.
Maintaining Repellency Over Time
The repellent properties of cedar chips inevitably diminish as the volatile oils evaporate into the air. This natural decline is more rapid in open environments like a garden or yard compared to a closed storage chest. Over time, the surface of the chips can develop a slight film or coating from exposure to air and dust, which further seals in the remaining oils.
To restore the repellent potency, a simple physical action is usually sufficient to release fresh oil from the wood’s interior. Lightly sanding the surface of cedar blocks or chips with fine-grit sandpaper removes the outer layer and exposes the oil-rich wood beneath. Alternatively, chips can be refreshed by applying a small amount of pure cedar essential oil directly onto the wood. This process recharges the chips, renewing their strong, insect-deterring aroma.