Bee hatch

What to do in case of a carpenter bee infestation

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Q: How to control carpenter bees?

A: If you’re like many homeowners with a question about carpenter bees, you’ve probably noticed round holes about ½ inch in diameter in siding, eaves, deck railings, or other wood, and you worry about the extent of structural damage they cause. . But if you’re also a buzz-loving gardener and appreciate the crucial role pollinators play, you might have been delighted to see large, but mostly black, bees bustling about in your flower beds and vegetable patches. They are carpenter bees in a different role.

Although too large to penetrate tubular flowers, such as penstemons, carpenter bees pollinate many flowers, including those of tomatoes and eggplants. And therein lies one of the problems with how to control them: you need to prevent them from damaging your home, but you don’t want to kill them all – especially now, when so many pollinator populations are in decline.

To find an effective strategy, it helps to understand a little about their lives and the tunnels they have dug. Carpenter bees are about the same size as bumblebees, up to about an inch long. There are many species of both types, but the best way to tell them apart is by their abdomen, the largest part of their body. Carpenter bees have shiny, often black abdomens, while bumblebees have hairy, often yellow abdomens.

Bumblebees usually nest in colonies in the ground and sting if anyone approaches the nest, while carpenter bees nest alone in wood and rarely sting. Male carpenter bees can be very aggressive if you approach their nests, but that’s bravado: they don’t have a stinger. Females have stingers but rarely sting unless attacked.

Because carpenter bees do not form colonies or have a caste system with queens and workers like bees or bumblebees do, they are classified as solitary bees. But they are far from being loners: if you have one, you probably have several, as children tend to hang out in the same place as parents. In the wild, they dig dead but undecomposed trees. In homes, they are often found in siding, deck railings, eaves or fascia boards. Unlike termites, you usually don’t have to worry that they’ve burrowed themselves into framing or floor joists because carpenter bees usually stay in the wood that’s on the outside surface. The holes you see go straight into the wood, but only about an inch, then twist and follow the grain lines of the wood.

Adult males and females overwinter in tunnels that were used for egg laying the previous season. They emerge in the spring and mate. Then, females extend existing tunnels or drill new ones, using their mandibles or mouthparts. The male guarding the hole, the female goes back and forth to supply the end of a tube with a ball of “bee bread”, a mixture of pollen and nectar. Thereupon she lays a single egg, then walls this cell with chewed wood pulp. This process is repeated about five to eight times, with the adults resting in the tube overnight before returning to work the next day.

The eggs hatch and the larvae grow out of sight, feeding on the bee bread. Later in the summer, the new bees emerge and fly around the garden until the weather turns cold and they find an empty tube where they can overwinter and start the process over. Female carpenter bees often live for several years, while males die after about a year.

The first year a tunnel is in use, it may be only four to six inches long, which does not significantly weaken the wood, although the hole may let water in, which may lead to rot. But when a tunnel is used and extended year after year, it can go much further, up to 10 feet, according to a prospectus from Clemson University. These annual additions can weaken the wood, especially if other bees have tunneled into the same piece.

So how do you stop them from doing it? Carpenter bees almost always dig tunnels in bare wood. Painting exterior wood is therefore one of the best long-term solutions. But if bees have already eaten away at your home, you can’t just plug the holes and paint. You must first replace the wood or kill the bees hiding in the tunnels, as any live bees left inside can gnaw their way. If you don’t want to replace the wood or use pesticides, it is possible to trap the bees, plug the holes, then look for new holes and keep trapping and plugging until there are no more. have more holes. But you will need to commit to frequent inspections.

If you opt to try and eliminate the problem with a single sweep, effective pesticides include sprays and powders, which you should apply just where they will target the bees in the tunnels of your home. An aerosol that foams or has a straw tip is much easier to use in a targeted way than a liquid that is diluted and applied with a garden sprayer. Spectracide carpenter bee and ground-nesting yellow jacket killer ($5.47 for a 16-ounce can at Home deposit) is an example of a foam product.

To dust the holes, use a device with a small bellows and a wand, like the Bellows Duster ($14.98 from domyown.com). The site sells a few different powders, as states vary in what is legal to use. Retailers should only sell what is allowed in your state. You can also do a web search for your state and the words “carpenter bees” and “extension,” for advice approved by your state’s land-grant college or university.

After treating a hole, wait 24 hours, then plug the hole with a short length of wood dowel coated in wood glue or steel wool coated in putty. Or you can use snap-on products, such as Trebor’s plastic plugs ($6.08 for a 20 pack of domyown.com).

Treat the holes in the evening, when the bees are in the tunnels. If the holes are hard to reach or your schedule prevents you from plugging the holes 24 hours after treating them, consider calling in a pest control professional. Be sure to talk about their process, though, and make sure they don’t plan on spraying large areas, which could harm other insects. Pesticides labeled for use against carpenter bees can also kill other insects.

You can also buy a trap, like the BeesNThings Outdoor Bee Trap ($19.98 at Lowe’s). Or you can make a trap by building a box about five inches on all sides out of wood. Drill ½ inch diameter holes on two sides that slope slightly upwards. In the bottom, drill a hole sized for the neck of a plastic water bottle. Twist an empty bottle into the hole and hang the trap near where the bees are active. The bees can then enter, fly towards the light passing through the bottle below and not be able to find their way.

A problem at home? Send your questions to localliving@washpost.com. Put “How To” in the subject line, tell us where you live, and try to include a photo.