Borer bees are more commonly known as carpenter bees. They are similar in size and shape to bumblebees, but their upper torsos are black and shiny, while bumblebees are hairy with some yellow. These bees bore holes into wood to create their nests. Borer bees prefer untreated, unpainted wood to drill into. Perfectly round holes approximately 1/2 inch in diameter are a sign of a borer bee infestation. Borer bees tend to return to the same nests year after year, so if you see holes in your home's exterior, chances are that borer bees will return to those nests in the spring.
Treatment for a borer bee infestation differs from treatment for bumblebees, because commercial insecticide sprays are not effective ways to poison a borer bee nest. For best results, treat borer bees just before spring, so that queens and their eggs will be killed.
Put on the face mask and rubber gloves. Diatomaceous earth isn't toxic, but it is a very fine powder that can irritate the lungs and skin of people with allergies or sensitivities.
Remove the bulb from the shaft of the turkey baster. Pour the diatomaceous powder into the bulb. Gently tap the bulb onto a hard surface, to allow the powder to settle. Repeat the fill/settle process until the bulb is completely full. Reattach the shaft to the bulb.
Insert the tip of the turkey baster into one of the holes that the borer bees created. Squeeze the baster's bulb to release some of the diatomaceous earth into the nest. Repeat this process in each of the holes.
Dispose of the mask and gloves. Dispose of the turkey baster or write the words "diatomaceous earth use only" on it, so that it is never used for food.
Leave the holes open, and wait for the borer bees to arrive. The bees usually appear when the weather starts to warm up. In the south, borer bees appear in early spring, while in colder climates they arrive during the summer.
Watch the nest holes to see when the bees enter the holes. Once the bees start climbing in, use plastic wood or a similar putty to seal the holes. When the borer bees are trapped in their nests with the diatomaceous earth, the powder will create tiny slices in their exoskeletons and dry them out. The powder does not poison them, but makes them die from dehydration.