Carpenter Bees

By
©1993-2012 Tim Carter

        
Summary: Carpenter bees rarely sting, but they do drill holes into bare or unpainted wood regularly to deposit their young. Pest control methods are primarily to get rid of the larvae by spraying insecticidal dust inside the holes. Another method to kill carpenter bees is to keep susceptible wood painted or apply chemical repellents every 2-4 weeks.

DEAR TIM: Every spring my house seems to attract large menacing bees or hornets. They show up out of nowhere and actually drill holes into the sides and other parts of my house. To make it worse, they keep me awake at night with their constant munching and crunching. What can be done to make these pest go away? What is the best way to repair the damage? Is there something I can do to repel these buzzing devils? Marie H., Philpot, KY

DEAR MARIE: I've got news for you. The insects you are talking about don't just stop by each spring, they are probably permanent residents. It sounds to me like you have an infestation of carpenter bees. The small holes that you see in your siding, soffits, window frames, etc. are actually the entryway to the nests where the bees raise their young. These bees love to drill into bare or unpainted softwoods. Redwood, pine, cypress and cedar seem to be their favorite wood species.

Look what those devils did to my gutter board! This channel was done by a carpenter bee in just a few days.
Look what those devils did to my gutter board! This channel was done by a carpenter bee in just a few days.
Carpenter bees are often confused with their cousins, regular bumble bees. A carpenter bee is usually 2/3 to one inch long and has a shiny black abdomen. A bumble bee is often slightly smaller and has a fuzzy abdomen with yellow markings. Bumble bees can and do sting with a vengeance. Male carpenter bees often frighten people because they fly close to their heads and hover as if they are going to attack. This activity is their only method of defense because Mother Nature failed to equip them with a stinger. Female carpenter bees can sting but they often only do so if you provoke them at or near their nesting sites.

Every spring male and female carpenter bees mate. The females then begin to build nests. They can drill new ones or remodel existing nest chambers from the previous year. The nesting chambers that extend from the entry holes can be extensive ranging from 6 inches to several feet long. The female carpenter bee is actually very resourceful and creates a maze like structure with twists and turns within the wood. There are small dead end branches off the main tunnels where a single egg is laid. The mama bee stores a glob of pollen next to the freshly laid egg. She then seals off this chamber. The baby carpenter bees develop into adults by the end of the summer but stay put in your wood siding, windows, trim, etc. until the following spring when they finally emerge to drill additional holes in your house.

Killing adult carpenter bees is not the best way to solve the problem. By the time you react to the bees presence, they have possibly already laid their eggs. The long term solution is to kill the developing larvae. Professional pest control people have found that blowing an insecticidal dust into the nest chambers seems to work best. If you do this early in the nesting process, the female carpenter bee carries the dust back to each egg site as she deposits the pollen food store for each egg. Look for a dust that contains a 5 percent carbaryl content. Use a sprayer or duster that has a long snout that can inject the dust deep into the wood.

Once the nests have been treated with dust, leave them alone for a week or so. This will allow the female bee plenty of time to distribute the dust within the chambers. Use small corks or pieces of wood dowel rod to fill the entry holes. Glue them in place once you have achieved a tight fit. The presence of freshly drilled holes tells you that new nesting activity is happening and that you must continue to dust the new chambers.

The best preventive measures are to keep susceptible wood painted. Semi-transparent stains are not an effective repellent. People who live in log homes or other wood sided structures that are not painted can apply chemical treatments, but these moisture sensitive chemicals often need to be re-applied every 2 to 4 weeks to prevent carpenter bees from boring into wood. This can be a maintenance headache, but is your only choice if you want the natural look of wood.



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Comments:

Welcome! I, Tim Carter, don't answer questions here. If you post a question here in the Comments Area, perhaps another visitor will help you. You need to go to the Ask Tim page if you want a question answered. Once there, look closely at how many weeks behind we are. Please be patient as you use this free service. If you have an emergency and need to talk to me, there is an option there for you.
Jeanette
29 May 2008, 16:01
How to get rid of carpenter bees.
GatorGene
22 Jul 2008, 17:29
NBS 30 added to stain is supposed to last as long as the stain does
Bob
20 Sep 2008, 06:53
Why are some trim boards tastier than others? The bees seem to favor only one board that was added on our house. At the giant home supply store the guy there said that EWP was a target for carpenter bees so I went with the more expensive cedar. Surely the industry has some guidelines on this.
Chad
27 Oct 2008, 07:32
These bees are not the real problem at my house. The birds now come by and pick at their holes to get the larvae out. So I end up with foot long holes in my cedar siding. My cedar has probably 100 holes on a large house. That will be fun to dust.

I had the local pest company spray my whole house with insecticide. This seems to have stopped the activity. I will have to redo it in the Spring and Fall every year for $300 a pop I guess.
matt
06 Jul 2009, 17:53
I have a problem with them too, im going to fill in the holes with little bit of concrete, sans, then paint away
Chad
22 Jul 2009, 13:16
matt,

Just get colored silicone paintable caulk. Color match your siding, and then paint or stain. Looks pretty good on our house.
Frank
16 Apr 2010, 15:37
I heard that 5% Sevin does not work very well compared to the 10% that was taken off the market? Any comments. I have been using it for years. Oh What I do is;
-First, I use a dusting of Sevin
Powder as far back into the chamber as possible.
-Second, I seal the hole and chamber with Liquid Nails,
-Third, I then plug the hole with a dowel rod.

-Fourth, I pray the ---tards don't come back
Jason
08 May 2010, 17:24
Check out <a href="http://www.carpenterbeesolutions.com">Carpenter Bee Solutions</a>. They offer two products that work very well. One is a trap for capturing carpenter bees. They other is a gel type solution that is inserted into existing holes to kill larvae and adults who check out the holes. A friend of mine had carpenter bee problems, but the combination of the traps and butter solved them.
Karen
24 May 2010, 16:56
I have always had some holes in a section of the porch but never thought too much of it. I did insulation work above those holes a year or so ago and thought I could see straight down through them, but don't remember.

I recently put wood putty to cover the holes to make things look nicer, but now I'm seeing at least one male and possibly a second bee hovering around the area.

I've read that covering the nest keeps them from burrowing out, but I'm concerned they'll go up through the insulation into the attic. There's at least 12" of insulation over that area with the kraft face side down. Would they eat through the krafting? Could they eat through insulation?

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