The belief that cedar products, such as wood, chips, or essential oil, can naturally repel spiders is a popular belief for people seeking chemical-free pest control methods. This aromatic wood has long been used in chests and closets to deter fabric-damaging insects. The distinctive scent of cedar comes from potent, naturally occurring compounds known to deter many pests. This article investigates the scientific basis of this claim and examines cedar’s effectiveness for managing spiders in a home environment.
The Scientific Evidence on Cedar’s Efficacy
The scientific evidence supporting cedar’s efficacy as a spider repellent is mixed and often species-specific. Cedarwood oil and its extracts are effective against certain arthropods, particularly clothes moths, termites, and carpet beetles. These pests are often killed by the oils or deterred from establishing colonies. However, the response of arachnids like spiders differs significantly from that of insects.
Their unique physiology means spiders may react differently to botanical compounds. While some studies indicate cedarwood oil can repel certain species, such as the wolf spider, the overall body of specific research is limited. Cedar’s effect on spiders is generally considered a mild deterrent rather than a reliable, long-term solution. This repellent action is primarily due to the strong odor overwhelming the spider’s sensory organs, making the area undesirable.
Chemical Compounds Responsible for Repellency
The repellent properties of cedar are directly linked to volatile organic compounds (VOCs) contained within the wood and its extracted essential oil. The most active of these compounds are sesquiterpenes, which include cedrol, cedrene, and thujone. These compounds are responsible for the wood’s characteristic scent and its activity against pests. The concentration of these compounds, particularly cedrol, influences the degree of the wood’s effect.
These VOCs disrupt the spider’s chemoreceptors, which are the sensory organs used for navigation, hunting, and communication. The intense aroma overloads these senses, creating an inhospitable environment that spiders instinctively avoid. The compounds interfere with normal physiological and behavioral functions.
Practical Application and Limitations
When using cedar products, the practical reality often falls short of the desired long-term repellent effect. Cedar blocks, shavings, or furniture release their active compounds slowly into the air. The primary limitation is the high volatility of the repellent oils, meaning the scent dissipates relatively quickly, especially in large or open areas. A small block of cedar in a large room will have a negligible impact on spider activity.
To maintain a minimal level of deterrence, the wood’s surface must be refreshed periodically, typically by light sanding to expose fresh, oil-rich layers. Cedar essential oil can also be applied as a spray, but this requires frequent reapplication, sometimes weekly, to sustain the necessary concentration of VOCs at entry points. This constant maintenance makes cedar a less practical option for comprehensive, whole-house spider management.
Proven Methods for Spider Control
Since relying solely on cedar is often ineffective, implementing reliable, scientifically supported methods is a better approach for spider control. A primary strategy involves exclusion, which means sealing potential entry points to the structure. Spiders can squeeze through surprisingly small gaps, so caulking cracks around window frames, doors, and utility penetrations is an effective physical barrier.
Habitat modification is another highly effective technique, focusing on removing conditions that attract spiders and their prey. This includes reducing clutter, especially in dark areas like basements, attics, and garages, where spiders seek shelter. Outdoors, removing debris, woodpiles, and heavy vegetation near the foundation discourages spiders from moving inside. Mechanical removal, such as consistently vacuuming or sweeping away webs and egg sacs, also reduces the population directly.