During this time of year I receive calls about worm-like, dark brown to black creatures that are invading people’s houses or garages. Most likely these are millipedes. Millipedes are not harmful in the yard, but can be a nuisance with the first spell of cool temperatures in fall. Millipedes will invade houses (sometimes in large numbers) to find warmth on concrete in and around garages and houses. At times, millipedes can become so abundant; they may constitute a “millipede invasion” entering homes and other buildings. Once they reach indoors, millipedes will die – no sprays are necessary.
Millipedes (sometimes called “wireworms” which are the larval stage of a beetle that feeds on plants in farm fields) have two pairs of legs per body segment. They are usually brown to black in color with an elongated body that is round. Millipedes have no poison claws or legs. Once disturbed, they usually coil up to protect themselves. Once found in the home they usually die due to desiccation, although in moist basements they survive longer.
Millipedes live in organic matter such as leaves, mulch, and piles of wood or wood chips. Over mulching and/or watering in the garden can cause millipedes to attack vegetable plants. Reducing mulch thickness, reducing watering schedules, or pulling mulch away from plants and allowing them to dry will help reduce the potential for invading millipedes. To prevent millipedes from entering the home, be sure that screens are tight, that moisture-holding material in window wells is eliminated, and that mulches are at least 6-8 inches away from the foundation. Outdoors, you may wish to treat a 10-15 foot wide barrier strip with carbamate insecticide (Baygon, Ficam, Seven) because they are fast-acting. People and pets should stay off wet insecticides, but can safely walk on the yard once the insecticide is dry.
Once millipedes have entered the house, the safest way to control them is to vacuum or sweep them up. In damp hiding places, an indoor insecticide labeled for this use can be applied. As with any chemical, be sure to read and follow label directions when using any insecticides.