Nosy pill woodlice (Armadillidium nasatum) are a common species in natural and managed landscapes throughout South Carolina.
©Adam Haberski, iNaturalist.org
Quick Guide to Sowbugs & Pillbugs
- Common Names: Sowbugs, pillbugs, woodlice, land isopods, rolly pollies
- Scientific Group: Crustaceans (not insects)
- Where Found: Under mulch, leaf litter, rocks, logs, boards, and other moist areas
- Activity: Nocturnal
- Benefits: Recycle dead plant material and return nutrients to soil
- Potential Problems: May occasionally damage seedlings, roots, fruits, and vegetables
- Indoor Issues: Often found in damp basements, crawlspaces, and ground floors
- Best Control Method: Reduce moisture, shelter, and organic debris
What Are Sowbugs & Pillbugs?
Sowbugs and pillbugs are commonly found outdoors in South Carolina, especially under leaf litter, rocks, logs, and boards. They are not insects but crustaceans, which makes them more closely related to lobsters and shrimp.
They breathe with gill-like structures and require moist conditions to survive. Both sowbugs and pillbugs are often called woodlice or land isopods. Despite the name, woodlice aren’t parasitic and are called such because of their close association with logs and other dead wood.
How to Identify Sowbugs & Pillbugs
An oak woodlouse (Porcellionides virgatus) with a clear view of its tail-like uropods on the right.
© Eric C. Maxwell, iNaturalist.org
Sowbugs and pillbugs are similar in appearance. Both are oval-shaped, with a rounded upper surface and a flat lower surface.
They can be grey to brown in color, about 1/4 to 5/8 inches long, and have overlapping body segments that resemble armored plates. Unlike insects, which have three pairs of walking legs, sowbugs and pillbugs have seven pairs of walking legs.
Differences Between Sowbugs and Pillbugs
While sowbugs and pillbugs appear similar, one key difference is that disturbed pillbugs can roll up into a tight ball through a process called conglobation, hence the nickname “rolly pollies”.
Sowbugs, on the other hand, are unable to roll up. Sowbugs can be further differentiated by the presence of two tail-like structures at their rear end, which are called uropods.
Sowbug & Pillbug Habits and Life Cycle
Both sowbugs and pillbugs have similar habits and biology. They are nocturnal, coming out at night to feed on decaying plants. Occasionally, some species are known to feed on carrion.
Sowbugs and pillbugs are inactive during the day and can be found in moist areas with high humidity, such as under rocks, boards, mulch, leaf litter, and soil, since they must stay moist to survive.
They do not bite and are completely harmless to humans and pets.
Sowbugs & Pillbugs Indoors
Although sowbugs and pillbugs normally live outdoors, they can occasionally make their way into homes, especially damp basements and ground floors of houses.
This usually occurs when there is a long, wet spring. Having many sowbugs or pillbugs invade a home is usually a sign that a large population exists outdoors.
They may establish populations in house plants.
Benefits of Sowbugs & Pillbugs
While sowbugs and pillbugs are primarily beneficial, recycling dead plant material and helping return nutrients back into soil, they can occasionally become garden pests.
The common pillbug (Armadillidium vulgare) occurs throughout South Carolina.
© Caleb Wardlaw, iNaturalist.org
Garden Damage Caused by Sowbugs & Pillbugs
They may feed on young plant shoots and their roots. Pillbugs have been documented damaging a variety of garden fruits and vegetables, including, but not limited to:
- Strawberries
- Tomatoes
- Cucumbers
- Lettuce
- Beans
How to Manage Sowbugs & Pillbugs Around the Home
Sowbugs and pillbugs rarely – if ever – require management. However, if these creatures become a nuisance in households, the key to effective control is to eliminate their preferred habitat by reducing the moisture, hiding places, and food sources they need to survive.
Reduce Moisture and Shelter
Remove leaf litter, mulch, lumber, rocks and similar materials from near the outside of the house.
Make sure any thick, braided door mats are not providing harborage underneath for sowbugs and pill bugs.
Also, make sure to elevate planters, flowerpots, and other outdoor objects (especially those with potentially moist bottoms) to allow air flow.
Properly ventilate basements and crawlspaces to decrease moisture.
Prevent Sowbugs & Pillbugs from Entering the Home
In addition, prevent sowbugs and pillbugs from entering the home by making sure windows and doors fit tightly, and cracks and crevices are properly sealed.
Nosy pill woodlice (Armadillidium nasatum) and curly woodlice (Cylisticus convexus) can often be found on the underside of partially decayed logs. © Winston Cornish, iNaturalist.org
© Caleb Wardlaw, iNaturalist.org
How to Control Sowbugs & Pillbugs in Gardens
Avoid overwatering in gardens, which can create desirable conditions for sowbugs and pillbugs.
Remove excess mulch, grass clippings, leaf litter, or other dead plant materials in the garden bed.
If there is concern that sowbugs and pillbugs are damaging your plants, try going out at night to see if they are the cause before resorting to chemical control options.
Chemical Control for Sowbugs & Pillbugs
If necessary, an appropriately labeled pesticide can be applied to foundation walls, crawlspaces, unfinished basements, and plant beds that border the home.
Applications made to mulched areas should be made with just enough water for the insecticide to penetrate through the mulch to reach the soil.
Insecticides are not recommended for indoor control because sowbugs and pillbugs dry out and die quickly inside a house.
Indoors, they can be easily removed with a vacuum or broom and dustpan.
Garden Insecticides for Sowbugs & Pillbugs
When addressing sowbugs and pillbugs in gardens, it is first advised to remove dead plant material and debris that may provide their preferred breeding sites and habitat.
Many common garden pesticides are effective, including:
- Sprays
- Baits
- Granular products
Permethrin-based and other contact insecticides have proven effective, which can be applied to plant beds and hiding areas for sowbugs and pillbugs.
Always use caution and follow label directions when applying any chemical controls.
Originally published 05/99
