Millipedes are generally harmless arthropods that primarily function as decomposers, breaking down dead plant material in the soil. They are not typically a direct threat to healthy, live plants. However, when environmental conditions are ideal, their populations can rapidly increase, leading to large numbers seeking shelter indoors or becoming a nuisance. Effective management focuses on altering the habitat that allows them to thrive.
Identifying the Source of the Infestation
Millipedes are strongly attracted to areas with excessive moisture and abundant decaying organic matter. They congregate under thick layers of mulch, leaf litter, rotting logs, or poorly draining areas near foundations. Their presence indicates that the soil environment provides a readily available food source and sufficient dampness to prevent desiccation.
Properly identifying the creature is necessary for effective treatment, as millipedes are often confused with centipedes. Millipedes move slowly, have a rounded, cylindrical body shape, and possess two pairs of legs attached to most body segments. Centipedes, conversely, move quickly, have a flatter body, and only have one pair of legs per segment, making them predators rather than decomposers.
Modifying Environmental Conditions for Long-Term Control
The most durable solution for controlling millipede populations involves making the soil environment less hospitable. Since millipedes require high levels of moisture, improving soil drainage is a primary focus, especially in garden beds or around the home’s foundation. Addressing leaky outdoor faucets, ensuring gutters direct water away from the house, and avoiding overwatering potted plants will reduce the dampness they seek.
Managing the amount of organic debris on the soil surface is an effective cultural control method. Thinning mulch layers to no more than two inches removes the deep, moist cover under which they thrive and feed. Removing piles of leaves, grass clippings, or rotting wood from close proximity to the garden or structure eliminates prime breeding and shelter sites.
For houseplants, ensure the pot has adequate drainage holes and that the potting mix is not excessively compacted, which retains too much water. Good air circulation around the plants helps the top layer of soil dry out more quickly between watering. These habitat alterations disrupt the millipede life cycle and prevent future population growth.
Immediate Physical Removal and Trapping Methods
For immediate, non-chemical reduction of existing populations, physical removal methods can be deployed. Large clusters of millipedes can be swept up with a broom and dustpan or removed using a shop vacuum, which provides relief in high-traffic areas. The vacuum bag should be sealed and discarded immediately to prevent them from crawling out.
Temporary moisture traps can be established to capture large numbers overnight. Placing pieces of wet newspaper, cut sections of melon rind, or slices of potato on the soil surface provides an irresistible, damp food source. Millipedes will congregate underneath or inside these traps, which can be collected and disposed of the following morning.
Creating physical barriers can prevent millipedes from entering structures from the soil. Sealing cracks and crevices in the foundation or around door thresholds limits entry points. Applying a strip of duct tape, sticky-side up, near known entryways acts as an effective perimeter trap.
Applying Targeted Treatments for Severe Issues
When environmental controls and physical removal are insufficient for a severe or persistent infestation, targeted treatments may be necessary. Diatomaceous Earth (DE) is a popular natural option, composed of finely ground fossilized algae skeletons. When millipedes crawl over the DE powder, the sharp edges scratch their exoskeletons, leading to dehydration and death.
DE should be applied as a thin, dry dust layer directly onto the soil surface, around foundation perimeters, or in crawl spaces where millipedes are active. Insecticidal soaps or pyrethrin-based sprays can be used for direct contact kills, though they offer little residual control once the application dries. These products require direct contact with the arthropods.
For extensive outdoor infestations, particularly when migrating into a building, residual granular or liquid pesticides may be applied to the exterior foundation and the surrounding six-to-ten-foot soil perimeter. These treatments create a chemical barrier that continues to kill millipedes after application. It is important to select products carefully and apply them strictly according to label instructions to minimize impact on beneficial insects, pets, and surrounding food crops.