Carpenters: Good or Bad?

I often receive questions about bugs from readers. Bugs is a really large umbrella for creepy crawly things that most people find distasteful. I am a bit of a cheerleader for these creatures as most are beneficial and very interesting once you get to know them.

A recent inquiry was about one of these little beasties that most of us consider an insect but is, in fact, a land crustacean. Crustaceans include lobster and crab. What, you may ask, do we have crawling around our gardens that are related to these delectable foods? In Newfoundland and Labrador, we call them ‘Carpenter bugs’, ‘Boat Builders’ or ‘Cafners’, the latter being a new one to me. The rest of Canada refers to them as ‘Sowbugs’ although there are many other names for them.

The reader’s question was about how to eliminate them from their hobby greenhouse. Before I answer that question, let’s talk about what these little guys do. 

Sowbugs hang out in damp areas such as basements, composts, soil mulch and any other habitat, such as greenhouses, which provides moisture and food. If you see them on the sidewalk, they are usually dead or hurrying to find a hospitable spot to hold up for a bit. If they dry out, they die, hence, you will not often see them basking about on the beach. That being said, if they are submerged for any length of time, they will drown. They are dependent on that sweet spot that provides just enough but not too much moisture. 

Carpenters feed on decaying matter such as wood, fungi or rotting plant material which is why most composts provide an ideal home for them. If you do the math (put two and two together) you will realize that they provide an indispensable service to us gardeners. These bugs and earthworms are the two most beneficial creatures for breaking down waste and turning it into compost.

I am a bit of a salesman for these little guys, but they do have a downside. They sometimes feed on cultivated plants (although it is rare) and they have a bit of a sweet tooth for strawberries. Can you blame them?

So, to answer the reader’s question, ‘Are these creatures causing damage in your greenhouse or are they in there because there is rotting wood or decaying plant matter to feed on?’ If they are just hanging out doing what they were intended to do, I would leave them alone. 

If they are indeed causing damage, here are a few things you can try to eliminate them.

Get rid of their habitat. Remove any rotting wood or decaying plant matter.

Keep the area outside of the greenhouse free from the two things listed above. If they have reason to hang out on the exterior of your greenhouse, it won’t be long till they find their way inside.

Since they do have a sweet tooth, use half a cantaloupe turned upside down to bait them. Carpenters are nocturnal so they will feed on this at night. In the morning you will likely find throngs of them hiding out and having a feeding frenzy. The murderous side of you may throw this in a bucket of water and watch them drown while the ‘live and let live’ side may opt to relocate to the compost where they belong.

Don’t want to waste a perfectly good cantaloupe? Roll up some damp newspapers with some apple slices inside and you will have the same results. The fruit is the bait, and the damp dark newspaper is the habitat they love.

If you are intent on a magic solution, a bit of diatomaceous earth sprinkled lightly around your young seedlings and strawberry plants should do the trick. Although this is an organic pesticide, exercise caution. Be sure to wear gloves, eye protection and wear a mask over your mouth and nose to prevent inhalation. 

Sowbugs are more beneficial than harmful. They clean up our debris, they don’t bite and they provide food for other insects such as spiders (and, yes, we do like spiders). I would not suggest putting them on the plate for your surf and turf but you can definitely encourage them to accompany the leftovers to the compost!

Janice, I hope I have answered your question.

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