Perfectly round holes in your post? You could have carpenter bees.

holes in wood post
Carpenter bee burrows

Have you ever spent a weekend in extreme humid heat trying to put a wood privacy fence up so you could separate your yard from the yard that has a pit bull? Well, we have – and when the fence was completed we stepped back and admired our work… until the next season.

Our fence posts have been invaded by carpenter bees and the image to the left shows their entrance and exit holes (usually perfectly round holes with sawdust near the base), along with what I suspect to be wood pecker holes (the really distorted holes closer to the top). As carpenter bees burrow through the wood they make multiple cavities (galleries) for which to lay their eggs.

May: Adults emerge from their nest to mate (shortly after, the male carpenter bee dies). female carpenter bees will either return to their nest to continue remodeling their home (in this case, my fence post) or create a NEW entrance hole for new galleries so they can lay ten or so eggs. She dies sometime [shortly] after all the housework and baby-making is completed.

June-July: The eggs hatch and the larvae feed on the food sources left in the galleries by the adult female carpenter bee. If timed right, this could be a great opportunity to use an insecticide dust puffed right into their newly constructed holes (the perfectly round ones – looking at the image on the left, that would be the hole near the middle of the post). Be careful though! The females, although docile, do have stingers and will attack is provoked.

August: The larvae have matured and will leave their galleries to buzz around pollinating plants, collecting food to store and annoying homeowners while they are trying to enjoy their lawn.

Winter: The adults that emerged in August will seek shelter again in their previous holes. There, they will hangout until the next spring and the whole cycle starts all over again.

What to do if you have carpenter bees: First off, don’t panic. The females are relatively tame – large, but tame. They will USUALLY only sting if they feel threatened. Males do not have stingers – they too are big and scary, but can’t do any real harm.

Carpenter bees tend to prefer soft woods (though have been known to burrow through hard woods too) and unpainted surfaces. Stained surfaces do not seem to help deter them. If you have carpenter bees annually in one particular area, try painting it.

EARLY spring, I’m talking March here, is possibly the best time to try rid your structure of these pests. Keep in mind that they are still in their wood galleries during this time. You may try insecticide dust, filling the open cavity with sealant or using wood filler to close the entrance/exit holes – or a combination of these. Don’t forget to paint so they don’t come back.


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