Sowbugs, often confused with insects, are terrestrial crustaceans, making them closer relatives to shrimp and crabs than to garden beetles. These small, oval-shaped creatures, sometimes called woodlice, are typically dark gray or brown and measure between one-quarter and one-half inch in length. They have a segmented, armor-like exoskeleton and two distinct tail-like appendages. Primarily detritivores, they play a beneficial role by feeding on decaying organic matter and helping to recycle nutrients in the soil.
Assessing Sowbug Damage in the Garden
Sowbugs spend most of their time breaking down dead plant material. However, they can quickly become garden pests when their populations grow too large or preferred food sources become scarce. Damage occurs when they shift their diet from decomposing organic matter to soft, live plant tissue, often seen in high-density populations.
The most vulnerable plants are tender seedlings and young transplants, which sowbugs can completely consume overnight. They also target parts of mature plants in direct contact with the damp ground, such as lower leaves, new roots, and soft fruits like strawberries or melons. To confirm sowbugs are the cause of the damage, gardeners should check plants at night with a flashlight, as these creatures are nocturnal and hide during the day.
Eliminating Harborages and Improving Drainage
The most effective, long-term strategy for managing sowbugs involves modifying the garden environment to make it less hospitable. Sowbugs require consistently damp, dark conditions to survive because they lack the waxy cuticle that protects insects from drying out. Therefore, reducing moisture and eliminating hiding spots are the first steps in cultural control.
Improving soil drainage is a significant step, accomplished by amending heavy soils with organic matter to prevent water retention. Adjusting watering practices is also helpful; irrigate early in the morning instead of the evening so the soil surface can dry out before the sowbugs become active. Utilizing drip irrigation rather than overhead sprinklers can further limit surface moisture, making the area less attractive to the pests.
Removing potential daytime hiding places, known as harborages, will significantly reduce the population. This includes clearing away piles of leaf litter, old boards, stones, and excess debris near plant beds. While mulch retains soil moisture, excessive layers provide ideal sowbug habitat, so keep mulch pulled several inches away from the base of plant stems. Using raised beds or planting boxes also helps, as they promote better drainage and aeration, drying out the soil surface more quickly.
Direct Removal Using Traps and Baits
Once cultural controls are in place, direct removal methods can be used to quickly reduce high sowbug populations. Simple traps exploit the sowbugs’ need for moisture and shelter. A common method involves placing scooped-out potato halves, melon rinds, or damp, rolled-up newspapers cut-side down near affected plants. Sowbugs crawl into these dark, moist spaces overnight, allowing the gardener to collect and dispose of the pests in the morning.
Physical barriers can protect vulnerable seedlings. Applying a light dusting of diatomaceous earth (DE) around the base of plants creates a sharp, abrasive barrier that dehydrates the sowbugs’ delicate exoskeletons. This natural product must be reapplied after rain or heavy watering to maintain effectiveness. Another option is using copper strips around the perimeter of garden beds, as the metal reacts with the sowbugs’ bodies to create a mild electric shock, deterring them from crossing.
For severe infestations, baits provide an efficient way to rapidly reduce the overall population. Baits formulated for slugs and snails, often containing iron phosphate, are also effective against sowbugs and are considered low-toxicity options. These pellets should be scattered lightly in the evening around plants or harborages where sowbugs congregate. Sowbugs feed on the bait and retreat to their hiding spots to die, which avoids leaving visible dead pests on the surface.