Treating carpenter bees

Dr. Cisse Spragins, founder and CEO, Rockwell Labs

Carpenter bees are a problem nationwide and active in warm months.

Unlike many bees, they are solitary insects. Females have stingers but are not aggressive. Males, identified by a yellow spot in the center of the head, do not have stingers.

The females damage structures by drilling into (but not eating) wood, particularly if it is unfinished, or there is significant damage to the finish. While it only looks like a small hole from the outside, the females will make a 90-degree turn once inside the wood and continue — for several inches up to a few feet. Along this main tunnel, female carpenter bees will create chambers to lay eggs. Woodpeckers may peck the holes looking for larvae.

The best prevention is to paint or varnish the wood. A repellent insecticide such as a botanical or a micro-encapsulated pyrethroid, applied in early spring, will deter new nest formation and should be reapplied in early summer. For existing infested holes, dust injection is one of the most effective approaches. A botanical dust will provide fast knockdown and strong repellency to help prevent reinfestation. After bees are killed, existing holes should be sealed to prevent reinfestation.