Iowa State University
Horticulture and Home Pest News

Sowbugs in the Landscape and Garden

This article was published originally on 6/7/2013

 Quiz Question:  What animal in your garden is most closely related to lobsters, shrimp, crayfish and crabs?
The answer:  Our common terrestrial crustacean, the sowbug.
That's right.  When most of us think of the crustaceans (lobsters and their relatives) we think of the edible crustaceans that live in the ocean or in fresh water.  But gardeners have a common and frequently-abundant lobster-relative that lives under the mulch in the garden and landscape. 
I’m sure you’ve seen the garden variety sowbug.  You usually find them under mulch, dead leaves, rocks, boards, grass clippings, and other debris on damp ground. 
Sowbugs are flat, elongate-oval in shape and up to 3/4 inch in length.  They vary from brown to slate gray to almost black.  Their distinctive appearance comes from the hard, armor-like, overlapping, plates on the top of each body segment that make them vaguely resemble little armadillos.  Sowbugs have no wings but they do possess well-developed eyes, two pairs of antennae, and seven pairs of legs.
Some sowbugs are called pillbugs or “rolly-pollies.”  These are slate gray in color and owe their name to the ability to roll up into a tight ball when disturbed (making them look like a pill, I suppose).  Sowbugs are incapable of curling up.
Active at night
Sowbugs use several “tricks” to obtain and conserve moisture.  One is they spend almost all their time in damp, dark cracks and crevices where moisture is abundant and where they will be protected from drying winds and sunshine. They generally cluster in masses to reduce water loss.  They stay close to the ground, and finally, they are primarily active at night when the humidity is higher and they can move about without desiccating.
More Beneficial Than Harmful
Sowbugs eat decaying leaf litter and vegetable matter.  Thus they are some of nature’s best “recyclers.”  They break up decaying plant matter and help speed the return of the nutrients to the ecosystem.
On occasion sowbugs may feed on tender transplants and seedlings.  I have also seen them feed on hosta leaves where the leaf rests against a stone wall or flat against the ground.  It appears our wet spring may be contributing to more-than-usual number of calls concerning sowbug damage in the garden.
Check at night to see if sowbugs are the cause of your disappearing seedlings or leaf-edge damage.  If you confirm sowbugs are the problem you might try to thin the herd by removing hiding places such as piles of leaves, grass clippings, fallen fruit, boards, stones and other debris.  Common garden insecticides such as Sevin or permethrin can be applied around the base of plants and to sowbug hiding places to further reduce the population. 
In the end, sowbugs are more interesting and beneficial than they are harmful.  If the weather would just cooperate, most vegetable plants would outgrow sowbug nibbling, and control would not be necessary. If control is warranted, do what you need to do to reduce damage while recognizing the benefit of sowbugs, our terrestrial crustacean.
Look for sowbugs under damp, decaying organic matter during the day.Look for sowbugs under damp, decaying organic matter during the day.