Pill Bugs On Cannabis: Are Roly Polys Bad For Your Plants?

By Rick Smith / October 3, 2026

Illustration of gray pill bugs on damp soil and leaf litter at the base of a young cannabis plant, one curled into a ball

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Quick answer: Pill bugs, also called roly polys, are usually minor pests, but in damp beds rich in organic matter they can chew cannabis seedlings, new roots and leaves touching the soil. They aren’t insects but small crustaceans that feed mainly on decaying plant matter. Drying the soil surface and clearing debris are the main fixes.

What Are Pill Bugs?

Diagram of a pill bug with four facts: seven pairs of legs, 1/3 to 3/4 inch, shell-like covering, curls into a ball

Pill bugs (family Armadillididae) and sowbugs (family Porcellionidae) are not insects or true bugs. The UC Statewide IPM Program describes them as soil-dwelling crustaceans in the order Isopoda. They’re also called roly polys, potato bugs or woodlice, and the name pillbugs is often written as one word.

Adults have seven pairs of legs, while insects have three pairs. They have a hard, shell-like covering made of segmented plates, an arched back, and antennae about one-quarter the body length. The adult body is about 1/3 to 3/4 inch long.

Color changes with age. The young are pale yellow to whitish and about 1/12 inch long when they leave their mother’s brood sac, while older ones are brown to dark gray.

Photo-style illustration of a gray pill bug curled into a ball on damp dark soil beside a piece of decaying leaf — Illustration

Pill Bugs vs. Sowbugs

Diagram comparing a pill bug that curls into a ball with a flatter sowbug that has two rear appendages

When disturbed, pill bugs commonly curl into a ball resembling a pill, hence the name. Sowbugs cannot roll into a ball and commonly scurry away. Pill bugs have a smooth rounded rear end, while sowbugs have distinct appendages protruding from their rear, and the top of a sowbug is flatter. Both are handled the same way in the garden.

Pill Bug Life Cycle

Females carry their eggs in a brood sac on the underside of the body. Eggs hatch about 1 month after being produced, and the young remain in the brood sac for about 2 weeks before they emerge. The young molt about every 1 to 2 weeks over a several month period as they grow into adults. Adults can live for 2 to 5 years.

Pill bugs and sowbugs overwinter as adults and emerge to breed in the spring. In Utah, they generally have 1 to 2 generations per year.

Do Pill Bugs Eat Cannabis Plants?

Diagram of what pill bugs eat: mostly decaying plant material, sometimes seedlings, new roots and lower leaves

Mostly, they eat dead plant matter. The UC Statewide IPM Program says sowbugs and pill bugs feed primarily on decaying plant material and are important decomposers of organic matter. However, they occasionally feed on seedlings, new roots, lower leaves and fruits or vegetables touching the soil.

Utah State University calls them usually minor pests that occasionally become numerous enough to damage roots, seedlings and foliage. They’re also opportunistic feeders following disease, slug, and other pest damage, so check for a second problem when you find them on a damaged plant.

What Pill Bug Damage Looks Like

Pill bug and sowbug feeding damage looks similar to slug damage, according to Utah State University. Look for ragged holes chewed between leaf veins, with damage concentrated around the soil level. Feeding at the base of seedlings can cause stunting or death.

Photo-style illustration of a cannabis seedling with ragged holes chewed in its first pair of serrated leaves, on damp soil — Illustration

Greenhouses and Potted Plants

Texas A&M AgriLife notes that pill bugs and sowbugs are seldom damaging under field conditions but can cause severe damage in greenhouses. They sometimes come indoors, which can be a nuisance, and in greenhouses Utah State suggests sealing off openings to prevent entry. If your seedlings are failing for no clear reason, also rule out the problems in 8 common diseases for weed seedlings.

Why Pill Bugs Show Up Around Cannabis

Diagram of a garden bed with four conditions that build up pill bugs: moisture, organic matter, little tillage, pH

Moisture and food bring them in. Utah State University says pill bug and sowbug populations increase in soils that are consistently moist, rich in organic matter, infrequently tilled, and neutral to alkaline in pH.

They hide by day. Pill bugs are nocturnal to avoid drying out, and spend the day in dark, damp places such as debris, mulch, decaying vegetation, wood or rocks. The UC Statewide IPM Program adds that they occur mostly hidden under organic litter or other debris on the ground and beneath low-growing plant parts. Moisture is the common thread, and overwatering cannabis covers the signs.

Photo-style illustration of an old wooden board lying flat on damp soil, with a cluster of gray pill bugs along its edge — Illustration

How to Check for Pill Bugs

Numbered diagram of three ways to check for pill bugs: look at night, lift debris, and set a halved potato flesh-side down

Look after dark. Adults and young are most active at night when humidity is up and temperatures are low.
Lift debris. Pill bugs and sowbugs hide under plant debris when temperatures are warm.
Set a trap. Place halved potatoes, or fruits such as apple, flesh-side down on the soil near seedlings, then check them every morning.

Utah State suggests starting to scout in spring, since adult isopods begin to emerge from the soil then, and using traps near susceptible seedlings to reduce numbers over time.

Photo-style illustration of one hand lifting half a potato from damp soil to reveal gray pill bugs on the cut side — Illustration

How to Keep Pill Bugs Off Cannabis

Diagram of six ways to keep pill bugs off cannabis, from drying the soil surface to cup collars around seedlings

Cultural steps usually work best. Utah State University says cultural management practices are generally most effective in preventing pill bugs and sowbugs from becoming a problem. The UC Statewide IPM Program recommends that you reduce the amount of decaying organic matter on soil and minimize wetness of the soil surface.

Water less often, to the extent that still keeps plants growing well.
Irrigate early in the day so surfaces are drier by evening.
Keep compost and mulch back from plants.
Use raised beds, plastic mulch instead of organic material, and drip or furrow irrigation instead of sprinklers. Black plastic mulch may be more effective at discouraging them than white or clear plastic.
Remove damp sheltering sites, such as piles of plant debris, boards or wood.
Protect young plants with a barrier, such as a cup with the bottom cut out placed around the seedling, and plant extra seedlings where numbers are heavy.

Natural enemies help too. Utah State lists the woodlouse spider, lizards, centipedes, ground beetles and nematodes as predators of pill bugs and sowbugs. Slugs and snails are a separate problem, with their own section in protect marijuana plants from pests and bugs.

Frequently Asked Questions

Pill bug fact card: seven pairs of legs, about 1/3 to 3/4 inch long, 2 to 5 years, and most active at night

Are Pill Bugs Bad for Cannabis Plants?

Usually not. The UC Statewide IPM Program says pill bugs feed primarily on decaying plant material and are important decomposers. They occasionally feed on seedlings, new roots and lower leaves, and Utah State University calls them usually minor pests. Texas A&M AgriLife notes that they can cause severe damage in greenhouses.

Do Roly Polys Eat Cannabis Roots?

Sometimes, but roots aren’t their main food. The UC Statewide IPM Program says pill bugs feed primarily on decaying plant material and occasionally feed on new roots and seedlings. Utah State University adds that they can become numerous enough to damage roots when soil stays consistently moist and rich in organic matter.

Are Pill Bugs Insects?

No. Pill bugs and sowbugs are soil-dwelling crustaceans in the order Isopoda, not insects or true bugs. The UC Statewide IPM Program points out that adults have seven pairs of legs, while adult insects have three pairs. They also have a hard, shell-like covering made of segmented plates rather than insect body segments.

What Is the Difference Between Pill Bugs and Sowbugs?

Pill bugs can roll into a ball and have a smooth, rounded rear end. Sowbugs cannot roll into a ball, commonly scurry away when disturbed, and have two distinct appendages protruding from the rear. The top of a sowbug is also flatter, according to the UC Statewide IPM Program. Both are managed the same way.

Why Are There Pill Bugs in My Cannabis Pots?

Damp mix and decaying plant matter attract them. Utah State University says populations build up in soil that’s consistently moist and rich in organic matter. Reduce decaying organic matter on the soil and minimize surface wetness. Water less often while still keeping plants growing well, and keep compost and mulch back from plants.

How Long Do Pill Bugs Live?

Adults can live for 2 to 5 years, according to the UC Statewide IPM Program. Eggs hatch about 1 month after being produced, the young stay in the mother’s brood sac for about 2 weeks, and they molt about every 1 to 2 weeks for several months before becoming adults. In Utah they have 1 to 2 generations per year.