Quick answer: Woodlice (also called pill bugs or sow bugs) throng damp, dark spots — under mulch, in basements, and near leaky pipes. Fix moisture first, seal gaps, clear decaying plant debris, then use food-grade diatomaceous earth and a vinegar spray on travel paths. Most indoor sightings drop within 1–2 weeks once the damp habitat is gone.
Key Takeaways
- Woodlice are crustaceans, not insects — they need moisture and die quickly in dry air
- Moisture control and sealing entry points beat any spray for long-term results
- Food-grade diatomaceous earth along baseboards and foundation edges is the best dry barrier
- They feed on decaying organic matter, not sound structural timber like termites do
- Clear leaf litter, over-wet mulch, and compost piles against the house to cut outdoor populations
| Method | Best for | Effort | Pet notes |
|---|---|---|---|
| Fix moisture | Any indoor sightings | Medium | Safest long-term fix |
| Seal entry points | Repeat invaders | Medium | Safe |
| Clear mulch/litter | Foundation populations | Low–medium | Safe |
| Food-grade DE | Travel paths, dry areas | Low | Avoid breathing dust; keep piles away from pets’ faces |
| Vinegar spray | Spot kills only | Low | Safe when dry; not for natural stone |
| Essential oil perimeter | Optional scent barrier | Low | Keep oils away from cats |
What Are Woodlice?
Woodlice are small land crustaceans related to shrimp and crabs. Common names include pill bug, sow bug, roly-poly, and woodlouse. Pill bugs can roll into a ball when threatened; sow bugs cannot. Both prefer cool, humid microclimates and are mostly active at night.
They are harmless to people and pets. Indoors they are a nuisance signal that something is too damp. Outdoors they help break down leaf litter — a problem only when numbers explode next to foundations or seedlings.
Why You Have Woodlice
Woodlice follow water and soft, rotting organic matter. Typical attractants:
- Leaky pipes, condensation, or poor bathroom/basement ventilation
- Mulch, leaf piles, or firewood stacked against the foundation
- Gaps under doors, cracked weatherstripping, and unscreened vents
- Overwatered plant pots and saucers that stay wet for days
If you see many indoors, treat the moisture source — not just the bugs you spot on the floor.
8 Natural Methods to Repel Woodlice
Method 1: Fix Moisture First
Dry air is the strongest woodlice repellent. Repair dripping taps and pipe joints. Run a dehumidifier in damp basements (aim for under ~50% relative humidity). Improve airflow in bathrooms and laundry rooms. Empty plant saucers and avoid leaving wet towels or cardboard on concrete floors.
Method 2: Seal Entry Points
Caulk gaps around windows, doors, and utility penetrations. Fit door sweeps. Screen crawl-space and foundation vents with fine mesh. Woodlice squeeze through surprisingly small openings when drawn by indoor humidity.
Method 3: Remove Habitat Against the House
Pull mulch and leaf litter 6–12 inches back from the foundation. Store firewood elevated and away from walls. Turn compost regularly and keep bins off the house wall. Replace constantly soggy mulch with a thinner, drier layer or gravel strip next to the foundation.
Method 4: Food-Grade Diatomaceous Earth
Apply a thin, barely visible line of food-grade diatomaceous earth (DE) along baseboards, under sinks, and along the exterior foundation where woodlice travel. DE abrades their soft undersides and dehydrates them. Reapply after heavy rain or mopping. Avoid breathing the dust — wear a mask when applying.
Method 5: Vinegar Contact Spray
Mix equal parts white vinegar and water in a spray bottle. Spray directly on woodlice you see and wipe damp corners. Vinegar is a contact treatment, not a lasting barrier — pair it with drying and sealing. Do not use on natural stone that can etch.
Method 6: Essential Oil Perimeter (Optional)
Strong scents can discourage crawling pests on hard surfaces. Mix 15–20 drops of peppermint, tea tree, or citrus oil in 1 cup of water with a few drops of dish soap. Spray along thresholds and windowsills weekly. Reapply often — oils fade quickly. Keep concentrated oils away from cats and never apply undiluted oils to pets or skin.
Method 7: Vacuum and Trap
Vacuum visible woodlice and empty the canister outdoors into a sealed bag. Shallow dishes of dry DE or a damp newspaper left overnight in a problem corner can concentrate them for morning disposal — then remove the damp lure so you are not feeding the problem.
Method 8: Garden Hygiene and Natural Predators
Keep beds tidy, avoid overwatering, and thin dense groundcover against walls. Birds, frogs, and ground beetles eat woodlice outdoors; a healthy garden supports that balance better than constant spraying. For seedlings, use copper tape or raised, well-drained trays so woodlice cannot hide under constantly wet pots.
Prevention Checklist
- Keep indoor humidity in check year-round
- Inspect under sinks and around water heaters monthly for leaks
- Maintain a dry, clear strip along the foundation
- Refresh DE lines after storms
- Do not store damp cardboard or newspapers on basement floors
When to Call a Professional
Call pest control if you have a heavy indoor infestation that returns after moisture repairs, or if you also see structural wood damage — that pattern is more consistent with other wood-destroying pests than with woodlice alone. A professional can confirm the species and check for hidden leaks.
Related Guides
- How to get rid of spiders in your house naturally
- How to repel silverfish
- Free home defense checklist
Frequently Asked Questions
Are woodlice dangerous?
No. They do not bite, sting, or spread disease. They are mainly a moisture indicator and a nuisance indoors.
Do woodlice eat wood like termites?
No. Woodlice feed on soft, decaying organic matter. Sound structural timber damage usually points to other pests — have it inspected if you see tunnels or frass in solid wood.
Why do woodlice come inside at night?
They are nocturnal and wander when outdoor humidity drops or when indoor damp spots (bathrooms, basements) offer better cover.
Will bleach or bug bombs stop woodlice?
Fogging rarely solves the root cause. Dry the space, seal gaps, and remove decaying debris. Spot-clean with vinegar if needed; save harsh chemicals for confirmed infestations of other pests.
How long until woodlice are gone?
Once moisture and entry points are fixed, indoor numbers usually fall within 1–2 weeks. Outdoor populations near the foundation shrink as mulch and litter are pulled back and DE barriers are maintained.
What is the difference between pill bugs and sow bugs?
Both are woodlice. Pill bugs can roll into a ball when threatened; sow bugs cannot. Control methods are the same: reduce moisture, seal gaps, and remove decaying habitat.
