Pillbugs and Sowbugs Control and Prevention

Tips for Keeping Them Out of the House


Brian Gratwicke/flickr

Pillbugs and sowbugs are two tiny pests considered to be occasional invaders because they will enter homes and buildings. However, these hard little bugs actually survive better outdoors—particularly when they find a wet or very damp area in which to live—such as under rocks and wood on the ground.

In fact, these two common pests are not really insects, rather they are crustaceans and are, in fact, the only crustaceans that have adapted to living completely on land rather than water. Because of this, pillbugs and sowbugs have more characteristics of and look more like crayfish or lobsters than insects.

Pillbug and Sowbug Identification

Pillbugs and sowbugs look pretty much the same:

  • 1/4 to 1/2 inch long
  • 7 pairs of legs
  • 2 pairs of antennae, though one pair cannot be easily seen
  • dark gray to white; or may be solid colored or patterned
  • rounded bodies that are convex on top and concave on the bottom

But they are also different:

  • The many segmented body of the pillbug enables it to roll into the tiny ball in which it is often seen, and for which it is named - "pill" or, more commonly, "roly-poly."
  • Sowbugs have two tail-like appendages extending from the rear end of bodies, and they can't roll into a ball.

Pillbug and Sowbug Habits

Sowbugs and pillbugs:

  • Need moisture to survive
  • Can live up to three years in optimal conditions
  • Are most commonly found outdoors beneath stones, rocks, boards, leaf litter and other items lying on the ground where it is moist
  • May enter homes and buildings at ground level, into damp basements, or in crawl spaces. They will only survive, however, if moisture is found.
  • Generally come out from their harborage only at night—unless their shelter is disturbed
  • Are scavengers. They feed on a decomposing organic matter such as leaves and logs. They may also feed on young plants as well as the skin of cucumbers.
  • Are harmless to people, but can damage plants and seedlings with their feeding

Prevention and Control of Pillbugs and Sowbugs

  • Exclusion: As with most insects, rodents and other pests, one of the best ways to keep pillbugs and sowbugs from invading your home is building them out. That is, sealing all cracks, crevices and gaps in the foundation and around vents, cables, wires, doors and windows (especially at thresholds); repairing and maintaining screens; and keeping doors and windows shut. Particular emphasis should be paid to ground-level areas, as this is where the bugs most frequently enter.
  • Moisture Reduction: Because these pests cannot survive without moisture, repairing and eliminating any areas in the home that are wet or damp (such as basements, leaky pipes, cracked foundation areas, etc.) will help keep these pests from surviving or reproducing even if they do enter your home. It is also helpful to ensure that the property is graded away from the home so that water flows away rather than accumulating near the foundation.
  • Sanitation: Pillbugs and sowbugs will harbor in clutter, especially piles that have gotten moist from sitting. Because they feed on organic matter, they may also seek out these areas for food.
  • Indoor Chemical Control: Once the bugs enter the home, insecticides won't do much good. Rather the bugs can be controlled by simply vacuuming or sweeping when seen and controlling moisture and sanitation to disable survival.
  • Exterior Chemical Control: A perimeter application of an insecticide labeled for sowbugs/pillbugs and the area in which it is to be used can provide some preventive control in keeping these, and other occasional invaders, out of your home. According to the University of Kentucky, an insecticide may be applied "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."

Always read and follow all label directions when using any chemical pesticide.