The idea that cedar wood can repel insects is a long-standing claim, commonly associated with protecting wool clothing from moths in cedar chests and closets. This popular belief stems from the wood’s distinct, pleasant aroma, which is a natural defense mechanism evolved by the tree itself. People often look to this natural source as an alternative to synthetic chemical treatments for pest control around their homes and yards. The central question is whether this traditional, natural approach is genuinely effective against mosquitoes, which are a different and more immediate threat. To answer this, it is necessary to examine the specific chemical components within cedar and their measured effects on mosquito behavior.
The Repellent Compounds in Cedar
The anti-insect properties of cedar are due to a complex mixture of naturally occurring volatile organic compounds (VOCs) concentrated within the wood and its extracted oil. The primary component responsible for repelling insects is a sesquiterpene alcohol called cedrol, although other compounds like thujopsene also contribute to the overall effect. Cedrol is a major constituent of cedarwood oil, often making up a significant portion of its total volume. The tree naturally produces these chemicals to deter fungi, decay, and wood-boring insects. Against mosquitoes, these compounds disrupt the insects’ highly sensitive sensory organs, essentially overloading their ability to detect hosts by scent. The mechanism of action is often multi-faceted, potentially acting as a neurotoxin or interfering with essential pheromones.
Measured Effectiveness of Cedar Products
Scientific investigation reveals a significant difference in efficacy between highly concentrated cedar oil and passive cedar forms, such as mulch or wood chips. Concentrated cedarwood oil, often extracted through steam distillation, has shown promise in laboratory and field studies as both a repellent and a direct insecticide. The U.S. Environmental Protection Agency (EPA) recognizes cedarwood oil as a minimum-risk pesticide, acknowledging its capacity to deter or kill various pests. However, cedar oil often falls short when compared to synthetic repellents like DEET or Picaridin. While it offers a high initial repellency rate, its complete protection time is much shorter, often requiring reapplication within minutes or a couple of hours. In contrast, passive cedar materials, such as fencing or untreated wood, release VOCs too slowly into the open air, meaning the concentration of cedrol vapor is insufficient to significantly impact a mosquito’s ability to locate a host.
Practical Use in Mosquito Control
The most effective application involves concentrated cedar oil formulations, rather than relying on decorative wood products. When applying cedar oil to the skin, it must be properly diluted with a carrier oil, such as olive or jojoba oil, to prevent skin irritation. Users should follow the instructions for pure, therapeutic-grade oils intended for topical use. Concentrated cedar oil can also be used in diffusers or applied as a perimeter spray around outdoor gathering areas. For yard-wide control, horticultural-grade cedar oil can be mixed and sprayed onto lawns, shrubs, and mulch beds to target mosquito resting spots. This approach requires frequent reapplication, possibly every few weeks or after heavy rain, to maintain the necessary concentration of volatile compounds.