Woodlice prefer dark, damp places: understanding their habits makes field control easier

The woodlouse is a common arthropod belonging to the class Malacostraca, order Isopoda; in folk usage it is often called the damp bug, sowbug, or pill bug. Although its name contains the word "bug," it is not an insect but a crustacean more closely related to shrimp and crabs. Its body is oval, with a back made up of several shell segments, and when disturbed many species curl their bodies into a round ball, which is where the common name "pill bug" comes from.

Woodlice prefer dark, damp environments. During the day they often hide under stones, dead wood, leaf litter, and cracks in wall corners, coming out at night to move about and forage. They breathe through their moist body surface and gill-like structures, and they easily dehydrate and die if kept away from damp conditions for long, so they are very sensitive to changes in humidity. In dry, cold weather they move deeper into the soil or to more sheltered places.

From an ecological point of view, woodlice feed on decaying plant remains and can break organic matter down into fine humus, which is somewhat helpful for soil nutrient cycling. But when fields or greenhouses stay damp for long periods and debris piles up, their numbers may increase noticeably, and they then gnaw on seedlings, tender roots, and fruit close to the ground, causing losses in production.

The key to controlling woodlice is to improve environmental conditions. Promptly clearing crop residues, fallen leaves, and stones from the field and keeping the bed surface dry, thereby reducing their hiding places, is often more effective than using pesticides. When their numbers are large, vegetable leaves or potato pieces can be piled up in the evening as bait for concentrated collection, and combined with management measures such as ventilation and reducing humidity, the damage can generally be kept at a low level.