Rolly pollies, also known as pill bugs or woodlice, are common garden dwellers often mistaken for insects. These creatures are actually terrestrial crustaceans, placing them in the same class as shrimp and crabs. This classification explains their strong reliance on moist environments to survive. They possess seven pairs of legs and a segmented, armor-like exoskeleton. This armor allows the pill bug variety to roll completely into a tight, defensive ball when disturbed, while sowbugs, a related isopod, cannot perform this action and instead scurry away.
The primary diet of these isopods consists of decaying organic matter, such as fallen leaves, rotting wood, and plant debris, making them beneficial decomposers in a healthy soil ecosystem. They help cycle nutrients back into the soil. Problems arise when their population density becomes excessive or when their preferred food sources become scarce, especially during dry periods.
When conditions are unfavorable, the isopods will shift their diet to tender living plants, targeting vulnerable seedlings, new root growth, and soft fruits that lie on the soil, like strawberries. They are primarily nocturnal, meaning most damage occurs overnight. They spend the day hiding in dark, damp locations to conserve the moisture needed for respiration, a behavioral pattern that guides effective management strategies.
Cultural Control: Eliminating Attractants
The most effective long-term strategy for reducing pill bug numbers is modifying the physical environment to make the garden less hospitable. Since these crustaceans must have moisture to breathe, reducing excess dampness is the primary goal. Adjust irrigation by watering garden beds in the morning rather than the evening, allowing the sun to dry the soil surface before the isopods become active at night.
Switching from overhead sprinklers to targeted delivery systems like drip or furrow irrigation minimizes surface saturation, controlling humidity levels at the soil line. Allow the top layer of soil to dry out completely between watering sessions. Improving soil drainage through adding amendments or planting in raised beds can prevent water from pooling and creating damp havens.
Eliminating hiding places and food sources is another high-impact cultural control. Remove piles of decaying wood, leaf litter, grass clippings, and fallen fruit from garden beds and around the foundation of the home. If using mulch, pull it back a minimum of six inches from the base of young, susceptible plants, or switch to a coarser, faster-drying material like shredded bark instead of fine compost.
Non-Toxic Trapping and Removal Strategies
For immediate, localized population reduction, non-toxic trapping and physical barriers provide direct intervention. Passive traps can be set up using common household items that mimic the dark, damp conditions the isopods seek during the day. Place hollowed-out potato halves, melon rinds, or damp, rolled-up newspapers cut-side down on the soil surface overnight.
Check these traps early the following morning, as the nocturnal pill bugs will have retreated inside to hide. The collected pests can be dumped into a container of soapy water for disposal or relocated to a compost bin where they can resume their beneficial role as decomposers. Hand-picking is also effective for small infestations, especially when combined with a night-time search using a flashlight.
Physical barriers can protect individual, vulnerable plants like seedlings. Place a collar made from a cut-off toilet paper roll or the bottom section of a plastic cup around the base of the plant, sinking it slightly into the soil. Crawling pests have difficulty traversing the smooth, vertical sides of these barriers. While copper deters slugs and snails, its effectiveness against isopods is not as well-documented, though it can be used as a general perimeter defense.
Targeted Pesticide Application
When cultural controls and physical trapping methods fail to manage a severe infestation, a targeted application of specific products may be necessary. Food-grade Diatomaceous Earth (DE) is a non-chemical option that works as a mechanical insecticide. It is a fine powder composed of fossilized aquatic organisms whose sharp edges scratch the isopod’s protective exoskeleton, causing fatal dehydration.
Apply this product as a thin, dry dust barrier around the base of affected plants or in hiding areas where the soil is not wet. Since moisture neutralizes its effect, Diatomaceous Earth must be reapplied after any rainfall or watering. Always use food-grade DE and wear a mask during application to avoid inhaling the fine particles.
Pesticide baits are also available, but choose a product specifically labeled for pill bugs or sowbugs. Baits containing only iron phosphate for slug control are often ineffective against isopods. Baits that combine iron phosphate with a secondary active ingredient, such as Spinosad, target a broader range of pests including pill bugs, earwigs, and cutworms. These granular baits should be scattered thinly on the soil surface in the evening, rather than applied in piles, to create a broad feeding area and reduce the risk to pets and wildlife.