Sowbugs and Pillbugs
ENTFACT-439: Sowbugs and Pillbugs | Download PDF
by Michael F. Potter, Extension Entomologist
University of Kentucky College of Agriculture
Sowbugs and pillbugs are similar-looking pests which are more closely akin to shrimp and crayfish than to insects. They are the only crustaceans that have adapted to living their entire life on land. Sowbugs and pillbugs live in moist environments outdoors but occasionally end up in buildings. Although they sometimes enter in large numbers, they do not bite, sting, or transmit diseases, nor do they infest food, clothing or wood. They are simply a nuisance by their presence.
Sowbugs and pillbugs range in size from 1/4 to 1/2 inch long and are dark to slate gray. Their oval, segmented bodies are convex above but flat or concave underneath. They possess seven pairs of legs and two pairs of antennae (only one pair of antennae is readily visible). Sowbugs also have two tail-like appendages which project out from the rear end of the body. Pillbugs have no posterior appendages and can roll up into a tight ball when disturbed, for which they are sometimes called "roly-polies".
Biology and Habits
Sowbugs and pillbugs are scavengers and feed mainly on decaying organic matter. They occasionally feed on young plants but the damage inflicted is seldom significant. Sowbugs and pillbugs thrive only in areas of high moisture, and tend to remain hidden under objects during the day. Around buildings they are common under mulch, compost, boards, stones, flower pots, and other items resting on damp ground. Another frequent hiding place is behind the grass edge adjoining sidewalks and foundations.
Sowbugs and pillbugs may leave their natural habitats at night, and crawl about over sidewalks, patios, and foundations. They often invade crawl spaces, damp basements and first floors of houses at ground level. Common points of entry into buildings include door thresholds (especially at the base of sliding glass doors), expansion joints, and through the voids of concrete block walls. Frequent sightings of these pests indoors usually means that there are large numbers breeding on the outside, close to the foundation. Since sowbugs and pillbugs require moisture, they do not survive indoors for more than a few days unless there are very moist or damp conditions.
Minimize Moisture, Remove Debris
The most effective, long-term measure for reducing indoor entry of these pests is to minimize moisture and hiding places near the foundation. Leaves, grass clippings, heavy accumulations of mulch, boards, stones, boxes, and similar items laying on the ground beside the foundation should be removed, since these often attract and harbor sowbugs and pillbugs. Items that cannot be removed should be elevated off the ground.
Don’t allow water to accumulate near the foundation or in the crawl space. Water should be diverted away from the foundation wall with properly functioning gutters, down spouts and splash blocks. Leaking faucets, water pipes and air conditioning units should be repaired, and lawn sprinklers should be adjusted to minimize puddling near the foundation. Homes with poor drainage may need to have tiles or drains installed, or the ground sloped to so that surface water drains away from the building. Humidity in crawl spaces and basements should be reduced by providing adequate ventilation, sump pumps, polyethylene soil covers, etc.
Seal Pest Entry Points
Seal cracks and openings in the outside foundation wall, and around the bottoms of doors and basement windows. Install tight-fitting door sweeps or thresholds at the base of all exterior entry doors, and apply caulk along the bottom outside edge and sides of door thresholds. Seal expansion joints where outdoor patios, sunrooms and sidewalks abut the foundation. Expansion joints and gaps should also be sealed along the bottom of basement walls on the interior, to reduce entry of pests and moisture from outdoors.
Application of insecticides along baseboards and other interior living areas of the home are of little use in controlling these pests. Sowbugs and pillbugs which end up in kitchens, living rooms, etc. soon die from a lack of moisture. Removal with a broom or vacuum is all that is needed. For large infestations, insecticides may help reduce inward migration of these and other pests when applied outdoors, along the bottom of exterior doors, around crawl space entrances, foundation vents and utility openings, and up underneath siding. It may also be useful to treat along the ground beside the foundation in mulch beds, ornamental plantings, etc., and a few feet up the base of the foundation wall. (Heavy accumulations of mulch and leaf litter should first be raked back to expose pests for treatment.) Insecticide treatment may also be warranted along foundation walls in damp crawl spaces and unfinished basements.
Various insecticides sold in hardware/lawn and garden shops are effective, including Sevin, Dursban, diazinon, and permethrin (Spectracide Bug Stop). Treatment can be accomplished with a compressed air (pump up) or hose end sprayer.
CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!