Controlling the friendly Carpenter Bee

Jim Seymour
Carroll County Master Gardener

They are back. A week ago I stepped off our screened back deck and it was eyeball to eyeball with me. Hovering, looking, waiting. They are black and yellow and very quick. They are the Carpenter Bees.

These bumblebee-sized bees are borers. The drill holes in your wooden porch, garage, railings, outdoor wooden furniture and dead tree limbs. Their holes are almost perfectly round and range in size from a dime to a nickel.

Once inside they make a right angle turn and continue to bore down the grain of the wood forming a series of cells. The female carpenter bee deposits the pollen and nectar collected from flowers into each cell and then places an egg on these food masses. Once the larva has finished feeding it pupates into an adult carpenter bee before cold weather sets in.

Male and female bees that survive the winter mate and bore nests the following spring, usually April through June selecting the same sites from year to year.

The female does all the work in the nest-gallery. She makes as many as six sealed cells in a four to six inch tunnel. Development time from egg to adult is between one and three months. This boring can weaken wooden structures and make them unsafe. The yellow sawdust and waste matter may soil vehicles, furniture, deck surfaces and clothing, and is a good indicator of active nesting sites.

The female bee like any wasp or bee can sting but it is uncommon. On the other hand the yellow-faced male carpenter bee has no stinger and establishes a territory over several active tunnels by aggressively flying at whatever threatens his territory. The yellow marking on the males "forehead" almost forms a perfect square pattern. This marking helps to make identification quite easy. The male is harmless.

The most effective deterrent to these winged saw mills is a well painted structure. If tunnels are evident, treatment with an insecticide and sealing of the tunnel is recommend. Any wasp, hornet and bee aerosols are effective and most likely the easiest control materials to use.

Apply the aerosol material into the tunnel entrances and along exposed surfaces. After 2 days close the tunnel with a deep plug of putty or caulking compound. I recommend applying insecticides after dark to avoid possible stings by the female. Reinspection should confirm that activities have ended.

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