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A Greenhouse Millipede in Baltimore Co., Maryland (7/11/2013).

Millipedes are a group of arthropods. They have two pairs of legs on each body segment (except for the first three), this characteristic set them apart from the 6-legged insects, 8-legged spiders, and the centipedes that have one pair of legs on each body segment.

Millipede Habitat

They require moist habitats rich in organic matter to breed and develop. Therefore, they are commonly found in gardens, lawns, forests, and near streams and lakes.

Around homes, they are often found breeding in large numbers in flower beds, gardens, the lawn, leaf piles, mulch, near the roots of plants, and in the soil under plant pots and rocks that are moist, cool, and dark. They are detritivores, meaning they eat all kinds of dead and decaying organic materials. In this regard, they are good decomposers in the ecosystem.

However, at certain times during summer and fall, millipedes become restless and may migrate in large numbers from their normal living places to residents’ living spaces. Such mass migrations are often associated with weather changes or heavy rainfall and a period of dry and hot weather. Following heavy rains, thousands of millipedes will come out of their normal habitats to breathe and go wandering about to find dryer places to survive, and this is when heavy home invasions occur.

Millipede Anatomy and Invasion

In Alabama, the most troublesome home invader is the garden millipede, Oxidus gracills, also named the greenhouse millipede. Garden millipedes have a flat body, brown to black in color, and are about ½- to ¾-inch long, smaller than other millipede species. In addition to decaying organic materials, they also feed on seeds and live plants when no other food is available and become a pest in greenhouses.

Garden millipedes do not harm people and animals. Once they leave their natural habitats and get inside a building or on the carport floor, they will shrivel and die quickly due to loss of body water.

However, large numbers of them crawling into the house and dying on the carpet/floor can quickly become a seriously annoying nuisance. Additionally, millipedes release an offensive odor when disturbed or handled. They can also stain fabrics.

Do I need to control those inside homes?

Since millipedes do not live for more than a few days indoors, treatment inside the home and building is not necessary. Spraying these areas with insecticides does little to reduce their numbers. Even though you kill the ones that are there, more millipedes just keep wandering up from their breeding sites. A wet/dry vacuum and a broom/dustpan to remove them are often the fastest and most appropriate control. Place the millipedes in a plastic bag, seal the bag and deposit the bag in an outdoor garbage container.

What can I do to keep them outside?

Integrated Pest Management (IPM) is the way to go. Non-chemical exclusion is the best first line of defense. The key is to reduce moist breeding sites in and around the structures and prevent access to structures.

Tips to reduce moisture and breeding sites around structures.

  • Routine maintenance to create a dry environment around homes and structures by directing any water runoff away from around homes and structures, and eliminating water accumulation from pipe-leaking, irrigation, and air conditioner condensation.
  • Remove millipede food sources and habitat by keeping the landscape free of leafy debris and grass clippings. Keep leaves away from structures.
  • If a layer of mulch is preferred, keep it between 2 to 4 inches.
  • Dethatch the lawn because millipedes thrive in the dense thatch layer of plant material just above the soil surface.
  • Closely mow and edge the lawn so the lawn can dry more quickly and reduce the millipede habitat.
  • Keep trash cans, water barrels, and potted plants away from the foundation.
  • Do not have flowerbed and garden adjacent to structure, especially not near crawlspaces and basement.
  • Remove rocks, logs, firewood, and other items near foundations.
  • Keep the basement and crawlspace ventilated by installing a dehumidifier and vents. Install a plastic vapor barrier to cover the soil in the crawlspace.

Tips to prevent access to the structure.

  • Sealing cracks and crevices in the wall and foundation where millipedes and other pests might enter. Block the weep holes and fill large voids in walls around drainpipes and vents with non-toxic steel wool and put caulk or foam around the steel wool to keep it in place.
  • Install weather stripping or sweeps to doors.
  • Caulk around window and door frames and door thresholds.
  • Seal cracks behind baseboards where the wet floor may attract millipedes to hide out within your home.

Chemical Control

Chemical control may be necessary only if millipedes keep invading in large numbers and all the non-chemical methods do not reduce the occurrence. There are many products labeled for millipede control.

  • One of the options is applying EPA-approved safe organic products such as the diatomaceous earth (DE) powder. Treatments should be applied directly to potential entry points such as cracks, crevices, weep holes, voids, utility and pipe penetrations, vents, doors, windows, and visible gaps in walls and foundations. DE is not poisonous, but it causes insects to dry out and die by absorbing the oils and fats from the cuticle of insect skin, specifically lethal to crawling insects. It remains effective if being kept dry and undisturbed.
  • Products with residual contact insecticides for perimeter applications include Gamma-Cyhalothrin, dinotefuran, bifenthrin, cyfluthrin, or carbaryl. Insecticides should be applied to the perimeter of the home and structure in a 5- to 20-foot band, and around potential entry points. Rack back thick layers of mulch to allow treatment of the exposed soil. Of the formulations, wettable powders provide longer residual activity.
  • Important: Read and follow the label for application.

The chemical application can help reduce the number of millipedes that make it all the way inside the building but don’t expect complete control during periods of heavy millipede movement. Habitat management by removing unnecessary harborage opportunities and managing irrigation properly will reduce their presence.