Wasp killer can indeed kill spiders, but the product is not designed for this purpose and its use comes with significant drawbacks. The active ingredients in these sprays are potent neurotoxins that affect the nervous systems of many pests, including arachnids. While the spray eliminates a spider upon direct contact, the risks associated with using a high-powered, outdoor chemical indoors generally outweigh the benefit of a quick kill.
The Chemistry of the Kill: Why Wasp Spray Works on Spiders
Wasp killer sprays contain powerful insecticides, most commonly synthetic compounds known as pyrethroids. These chemicals are broad-spectrum neurotoxins that target the nervous system of both insects and arachnids. The primary mechanism of action involves disrupting the voltage-gated sodium channels in nerve cells.
Pyrethroids bind to these channels, preventing them from closing properly after a nerve impulse fires. This forces the nerve cells into a state of hyperexcitation, causing continuous firing of electrical signals. The result is a rapid onset of tremors, convulsions, and paralysis, often called the “knockdown effect,” which quickly immobilizes the pest. Although spiders and wasps have different respiratory systems, their nervous system structure is similarly vulnerable to this chemical disruption.
Practical Risks and Safety Considerations
Using a product formulated for outdoor wasp nests against a single indoor spider introduces several practical and safety hazards. Wasp sprays are designed with a high-pressure, long-range jet stream, often reaching 15 to 20 feet, allowing users to treat a nest from a safe distance. This powerful delivery system makes it nearly impossible to apply the chemical precisely to a small target without causing excessive overspray onto surrounding surfaces.
Many wasp killer formulations contain oily carrier solvents that help the insecticide adhere and provide residual killing power. When sprayed indoors, this oily residue can permanently stain paint, wallpaper, wood trim, and vinyl surfaces. The high concentration of airborne chemicals also poses a significant risk to indoor air quality, requiring extreme ventilation to dissipate the fumes.
The residue from pyrethroid-based sprays is particularly hazardous to non-target organisms, especially pets and children. Cats are highly sensitive to pyrethroids because their livers lack the specific enzymes needed to metabolize the compounds efficiently. Contact with a treated surface or inhalation of the residue can lead to severe toxicity in felines. For these reasons, most manufacturers explicitly label wasp killer as an outdoor-only product.
Recommended Alternatives for Spider Control
Safer and more targeted methods exist for managing spiders without the risks associated with high-concentration wasp sprays. For immediate elimination, a dedicated indoor spider or general household insecticide spray is a better choice. These products use less aggressive delivery systems and lower concentrations of active ingredients, minimizing overspray and often labeled as safe for use inside the home.
Non-chemical methods are the safest and most practical for dealing with individual spiders. Simply using a vacuum cleaner with a hose attachment is an effective way to remove a spider and its web instantly. For long-term, non-toxic control, applying diatomaceous earth (DE) to cracks, crevices, and wall voids creates a physical barrier. DE is a fine powder that works by physically damaging the spider’s exoskeleton, causing dehydration.