Garden Column for the Salisbury Post

Darrell Blackwelder

June 17, 2004

     There have been so many complaints about the millipede invasion; I decided to expand upon the subject even though I mentioned them in last weeks’ garden column.  While some in the county haven’t had the problem, others are literally swamped with the pest

     While millipedes sometimes enter in large numbers, they do not bite, sting, or transmit diseases, nor do they infest food, clothing or dry, structurally sound wood. When disturbed, millipedes often curl up into a "C" shape and remain motionless.

     Millipedes are attracted to dark, cool, moist environments that are rich in organic matter such as compost piles, heavily mulched shrub or flower beds, rotting logs, or the soil under logs and stones. Millipedes are scavengers, feeding primarily on decomposing vegetation, but occasionally they will damage soft-stemmed plants in gardens.

     Major nuisance problems usually occur when the conditions become too dry and the millipedes move to find moisture or now when it's too wet and water-saturated soils force them to the surface and higher ground where they often end up on concrete slabs, foundations and siding. All of these activities result in millipedes invading crawl spaces, basements and other areas of buildings. This usually means that there are large numbers breeding outdoors in the lawn, or beneath mulch, leaf litter or debris close to the foundation. Millipedes do not survive indoors for more than a few days.

     Pesticides are typically a short-term solution to a long-term problem. Emphasis should be placed first on reducing moisture conditions and access points. This can be done by removing leaves, grass clippings, heavy accumulations of mulch, wooden boards, stones, boxes, and similar items laying on the ground beside the foundation. This does not mean you can't have mulch around the foundation; simply keep it 6-12" away from the wall.      Prevent water from accumulating near the foundation, in basement walls or in the crawl space. Keep gutters and down spouts free of debris and use either splash guards or perforated pipe to reduce puddling.

     Repair leaking exterior water spigots and prevent water from puddling where there are drip lines from air conditioning units.

     Over-watering lawns may also contribute to millipede problems.

     Seal cracks and openings in the outside foundation wall, and around the sills of doors and basement windows. Install door sweeps on all exterior entry doors, and apply caulk along the bottom outside edge and sides of door thresholds.

     Application of insecticides along baseboards and other interior living areas of the home do not really stop millipede invasions. Insecticides applied along the interior foundation walls of damp crawl spaces and unfinished basements may help temporarily. However, correcting such moisture problem is far more important in preventing millipede and other problems. Dust formulations such as Sevin may work well in some areas, but you need to apply them in a way that keeps children and pets from coming into contact with the chemical. Perimeter sprays may also help but are rarely 100% effective in stopping the millipedes.

     The key to successful chemical control is spray volume. The spray must penetrate the soil, not simply lightly coat the surface. The best means of application for homeowners is a garden hose attachment. Treat a 2-5 foot wide area of ground along the foundation in mulched, ornamental plant beds and grassy areas, as well as an 18-24 inch wide vertical band of the foundation wall.

     Spraying mulch is ineffective because the chemical does not penetrate well and will breakdown more quickly.

Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County. For archived garden columns or other information, visit the Rowan County Master Gardener web site at www.rowanmastergardener.com , e-mail Darrell_Blackwelder@ncsu.edu or phone at 704-633-0571.