Millipedes migrate indoors seeking shelter from overly wet or dry outdoor conditions. These moisture-loving arthropods can appear in large numbers, leading homeowners to search for effective, non-chemical pest control solutions. Diatomaceous Earth (DE) is a widely accepted option for managing them. This fine powder provides a physical method of control that effectively stops millipedes without relying on traditional chemical pesticides.
Understanding Diatomaceous Earth
Diatomaceous Earth is a naturally occurring powder composed of the fossilized remains of diatoms, which are ancient, microscopic aquatic organisms. These organisms possessed hard outer shells made primarily of silica. Over millions of years, the accumulation of these silica-based shells created the chalky sediment that is mined and processed into DE.
For pest control, select food-grade Diatomaceous Earth. This grade is composed largely of amorphous silica and contains less than one percent crystalline silica, making it suitable for household use. Filter-grade or pool-grade DE is heat-treated, which converts the silica into a form that poses a significant inhalation risk and should not be used for pest management.
The Mechanism of Millipede Control
Diatomaceous Earth works as a mechanical insecticide, meaning it kills through physical action rather than chemical toxicity. Millipedes and other arthropods are protected by a waxy outer layer, the exoskeleton, which retains internal moisture. The dried DE powder is composed of sharp, abrasive particles when viewed under a microscope.
When a millipede crawls across the dusted surface, these microscopic edges scratch and compromise the protective waxy layer of its exoskeleton. The DE then acts as an absorbent agent, drawing moisture and oils out from the exposed internal tissues. This continuous loss of internal body fluid causes the millipede to die from desiccation, or severe dehydration, often within a few hours to a couple of days of contact. Because the method of action is physical, millipedes cannot develop a resistance to Diatomaceous Earth.
Applying Diatomaceous Earth Effectively
The efficacy of Diatomaceous Earth against millipedes relies on proper application, which must ensure the pest comes into contact with the powder. Millipedes frequently enter homes through small gaps, so applications should focus on creating a perimeter barrier around the foundation, as well as dusting window wells, door thresholds, and other known entry points. A thin, even dusting is more effective than a thick pile, as a heavy clump can be avoided by the millipede.
Applying the powder with a hand-held duster or bellows applicator helps ensure a fine, uniform layer and prevents clumping. Since millipedes are attracted to moisture, target damp areas or those close to the soil line. The powder loses effectiveness when wet, so outdoor applications must be reapplied after rain or heavy dew. Indoors, place dust in hidden cracks and crevices where millipedes travel, such as behind appliances or along baseboards.
Safety Considerations
While food-grade DE is non-toxic, certain precautions must be taken during the application process. The fine dust particles can irritate the respiratory system, so wearing a dust mask or respirator is recommended to avoid inhaling the powder. Ventilation should be maintained during indoor application to prevent airborne particle buildup.
Direct contact with the skin and eyes can also cause irritation or dryness, so using gloves and protective eyewear is a sensible measure. Although the powder is safe around children and pets once it has settled, keep them away from the immediate area during dusting. DE is non-selective, meaning it can harm beneficial insects like bees and earthworms through the same abrasive action, so outdoor application should be targeted and cautious.