Ohio State University Extension Fact Sheet

Entomology

1991 Kenny Road, Columbus, OH 43210-1090

Sowbugs and Pillbugs

HYG 2072-94

Sowbugs and pillbugs, sometimes called "woodlice," live outdoors, but they may occasionally enter homes in damp areas such as basements, first floor levels and garages. These creatures are a nuisance by their presence; they do not bite humans nor damage structures or household possessions. However, if present in large numbers, they can feed on young plants in greenhouses. Some may crawl into swimming pools and drown, causing complaints. Those that wander into homes usually die in a few days unless they find a moist place near a leaky pipe or in a damp basement, bathroom or laundry room.

Identification

Sowbugs are oval or slightly elongate with a flattened body and up to 3/4 inch long. They are wingless, brownish or slate gray, and possess well-developed eyes, seven pairs of legs and overlapping "armored" plates that make them look like little armadillos. Sowbugs have two tail-like structures on the rear end. Pillbugs are similar, except they lack the tail-like appendages and can roll up into a tight ball. Both are slow-moving crustaceans closely related to crayfish, shrimps and lobsters but not insects. The young resemble the adults, except they are smaller and lighter in color.

Life Cycle and Habits

Both sowbugs and pillbugs mate throughout the year, with most activity in the spring. The female carries the eggs, numbering from 7 to 200, in a brood pouch on the underside of her body. Eggs hatch in three to seven weeks and the young are white-colored. They remain in the brood pouch for six to eight weeks until they are able to take care of themselves. There may be one to two generations per year, with individuals living up to three years depending on weather conditions.

These creatures live outdoors, feeding on decaying organic matter and occasionally young plants and their roots. They may become pests in and around homes where flower bed mulches, grass clippings, leaf litter, rotting boards, trash, rocks and pet droppings are present. Adequate moisture is essential for their survival, and they group in masses to reduce water loss. On a hot day, they remain under objects on the damp ground and are active only at night due to lower temperatures and more humid conditions. They become inactive during the winter months except in heated buildings such as greenhouses.

Control Measures

Since sowbugs and pillbugs require moisture to survive, it is important to keep the house and outside as dry as possible.

Prevention

Remove hiding places such as piles of leaves, grass clippings, mulch in flower beds, fallen fruit, pet droppings, boxes, boards, stones and other debris from the foundation walls, doors, basement windows and other points of entry. Properly ventilate basements and subfloor crawl spaces to eliminate excess moisture. Repair and seal cracks and openings in the foundation wall, around doors, and around basement windows with caulking compound and weather stripping. Drain standing water and moist areas near potential points of entry.

Indoors, the use of fans and dehumidifiers will help dry out the basement and other damp rooms. These creatures can be collected with a broom and dustpan, vacuum cleaner or other mechanical means and discarded. Insecticide sprays usually are not needed indoors since sowbugs and pillbugs dry out quickly and die. However, household contact or residual sprays are sometimes used.

Chemical Control

Outdoors, apply a residual treatment (protective barrier) to the soil in a three to six foot band around the foundation walls, especially damp areas, surrounding the house and even underneath crawl spaces, at doorways, window wells and other potential entry sites. It is helpful to rake mulch, leaves, etc. away from the house foundation before treatment. Sprays or dusts of bendiocarb (Ficam), chlorpyrifos (Duration, Dursban, Empire, Engage), diazinon, propoxur (Baygon), carbaryl (Sevin), pyrethrins (Exciter, Kicker, Microcare, Pyrethrum, Safer) or resmethrin (Vectrin) are effective. Other labelled pesticides include acephate (Orthene), amorphous silica gel (Drione, Tri-Die), boric acid (Perma-Dust) and esfenvalerate (Conquer). Treatment of peat moss, leaves and bark used as plant mulches is important. Subsequent sprinkling with water will carry the pesticide down into the soil where these crustaceans hide. Materials such as fluvalinate (Mavrik, Yardex) are used outdoors.

Only the licensed pest control operator or applicator can apply bendiocarb + pyrethrins (Ficam Plus), cyfluthrin (Optem, Tempo), cypermethrin (Cyper-Active, Cynoff, Demon, Vikor), deltamethrin (Suspend), lambdacyhalothrin (Commodore), permethrin (Dragnet, Flee, Torpedo), propetamphos (Safrotin), and tralomethrin (Saga). Before application, always read and follow the pesticide label directions and safety precautions.

This publication contains pesticide recommendations that are subject to change at any time. These recommendations are provided only as a guide. It is always the pesticide applicator's responsibility, by law, to read and follow all current label directions for the specific pesticide being used. Due to constantly changing labels and product registration, some of the recommendations given in this writing may no longer be legal by the time you read them. If any information in these recommendations disagrees with the label, the recommendation must be disregarded. No endorsement is intended for products mentioned, nor is criticism meant for products not mentioned. The author, The Ohio State University and Ohio State University Extension assume no liability resulting from the use of these recommendations.