The roly poly bug, known as a pill bug or woodlouse, is a familiar sight in gardens and under stones. These small, grayish creatures often prompt the question of whether they pose a threat to cultivated plants. While they are capable of consuming living vegetation, their diet is overwhelmingly focused on dead organic material. Scientifically, the roly poly is classified as a terrestrial crustacean belonging to the order Isopoda, making it more closely related to shrimp and lobsters than to garden insects. They are primarily beneficial members of the ecosystem, which only occasionally become pests.
Understanding Their Primary Diet
Roly polies are categorized as detritivores, meaning their natural function is to feed on decaying matter. Their preferred food sources include rotting wood, fallen leaves, compost, and other dead plant debris. This dietary preference establishes them as natural recyclers, playing a significant part in the decomposition process. They consume this organic material and return the nutrients to the soil in the form of castings. This constant breakdown of debris and subsequent nutrient cycling contributes positively to overall soil health and fertility. By chewing up dead vegetation, they accelerate the process that makes nutrients available for living plants.
When Roly Polies Consume Living Plants
Consumption of living plants occurs when their preferred food sources are scarce or when their population density becomes extremely high. These terrestrial crustaceans require high moisture levels to breathe, so they are often drawn to damp environments like a well-watered garden. When an environment is exceptionally wet, or if there is a deficit of decaying material, roly polies may turn to live plants to meet their nutritional and moisture needs.
They are particularly attracted to tender, soft plant tissues. Young seedlings and emerging sprouts are especially vulnerable because their stems and leaves lack the rigid structure of mature plants. The damage often appears as irregular holes chewed through leaves or as complete severing of the plant stem near the soil line. Soft fruits that rest directly on the ground, such as strawberries and squash, are also a common target, often showing signs of superficial damage or hollowing.
Strategies for Managing Them in the Garden
If roly polies begin to cause noticeable damage, management efforts should focus on cultural and physical controls rather than broad elimination. The most effective strategy involves reducing the moisture and debris that create their ideal habitat.
Cultural Controls
Adjusting watering practices to water less frequently, or earlier in the day, helps the soil surface dry out before night when they are most active. Removing excess mulch, leaf litter, and old plant debris from around vulnerable plants eliminates their primary shelter and food source.
Physical Barriers and Traps
For immediate, targeted control, simple traps can be used. Placing hollowed-out citrus rinds or potato halves face-down on the soil attracts roly polies seeking moisture and dark shelter. These traps can be collected and emptied daily, relocating the crustaceans away from the garden beds.
Physical barriers also deter them. A thin layer of diatomaceous earth sprinkled around seedlings causes desiccation. Placing aluminum foil or paper collars around the stems of young transplants helps prevent them from chewing through the stalks.