Thursday, May 06, 2010

Bee Battles, Part Two

So I have these somewhat combative acting but generally sweet-at-heart bees cohabiting our home with us. What's not to like, right?

Well, there's the little issue of the holes that they drill into wood....

Just to be clear, carpenter bees do not eat wood. They eat pollen and nectar, and do an incredible service as native pollinators while they are eating. Carpenter bees do, however, dig their nests, tunnels that are called galleries, into wood.

The females chew these tunnels out of generally soft, unpainted wood. A typical hole is about 1/2" in diameter and is essentially perfectly round. It starts out perpendicular to the grain of the wood for 1-2", then turns 90 degrees to follow the grain of the wood. After the turn, a gallery is usually chewed out to a length of 4-6". (The reason that we inherited the carpenter bees was that the prior owners of our home used cedar for the trim boards and didn't paint it.)

When you think about it, this is a lot of wood chewing for a 1" long bee. Our intrepid female is chewing a tunnel the diameter of her bodythrough solid wood. Her speed averages 1" of tunnel constructed every 6 days, if she's starting from scratch. Not surprisingly, female carpenter bees prefer to reuse old galleries, if they can, rather than have to chew out new ones. I would prefer to reuse old galleries, too, if those were my choices.

Whether it's a new gallery or a refurbished old one, once the gallery is prepared, the female carpenter bee makes a ball of "bee bread," a mix of pollen and regurgitated nectar, which she deposits in the gallery. When the bee bread ball is complete, she lays an egg on top of the ball and then seals off that part of the tunnel with a wall of chewed wood pulp. Each female will make from 6 to 10 of these larval chambers, all in the same gallery, before she dies.

The egg hatches and the larval (baby) carpenter bee commences eating. The bee bread ball provided by his mother is sufficient food for him to complete his growth. He then pupates and finally takes adult form. From egg-laying to adult form is about 7 weeks, depending upon the temperatures. The new adults emerge around the end of August, then hibernate in their natal galleries over the winter. In April they re-emerge, mate, and the cycle starts all over. There is only one generation a year.

A single nest isn't that big a deal, but apparently a nest that's been used year after year after year can be expanded to include multiple tunnels for different females. The eventual length can reach 10'...and now you're definitely talking a structural problem in a building.

So I'm battling myself about what to do. I don't want my house to have structural issues because I've let the carpenter bees continue nesting unchecked...but we've painted the cedar trim now, so no new holes will be constructed. Will leaving the existing galleries really create such a major problem?

Carpenter bees are fantastic native pollinators, and native pollinators are particularly important these days, with all of the problems the honey bees are experiencing. Not to mention that I just love to share my home territory with a wide variety of living creatures.

I don't know. I do know that if I'm going to act, this is the time of year to do it so that I can exclude the bees from our house without chemicals and with minimal numbers of carpenter bees being lost. It's fairly early in the year. The males are still alive and guarding the nest sites, so I think that if I plug the holes thoroughly during the day while the bees are outside, I can force them to find new nesting sites.

My internal battle rages on....


Gardener on Sherlock Street said...

What to do, what to do?? If you can get them to relocate, I think I'd try that. Can they be captured and released in a wooded area?

Gaia Gardener: said...

That's what my husband wants to try. I suppose there is no reason not try that first of all - I have a couple insect nets I could dig out and put to use!