Hello Fellow Readers,
How about all the carpenters buzzing about – eastern carpenter bees, that is. Xylocopa virginica, the most common species, is wreaking havoc on my neighbor’s deck which is not inspired by their yen to eat wood. Rather, they’re nesting. Please don’t hold their carpentry against them though, they are important pollinators in a world where pollinators are drastically in decline; dangerously so for the future of our food. (Link to a previous column How Can it Bee? )
An exterminator mistook Lucia’s dilemma for termites. Not the case. The explosions of sawdust are from bees emerging from their tunnels called galleries. They overwinter there and surface come spring to mate. Then the females gather nectar and return to build a pollen plug in a chamber of the gallery on which to lay eggs. She’ll lay one egg per chamber often boring new tunnels in the gallery to accommodate her six to ten eggs before closing the tunnel with wood chips for her baby’s protection. Then the mom bee dies. In three months, her larvae become adults who often return to the same gallery to overwinter. That’s when you’ll see woodpeckers pecking for lunch.Carpenter bees are often confused with bumblebees. Both are docile and rarely sting. In fact, only the female carpenter bees have stingers. The stinger-less males merely bombard for protection. Intimidating but harmless. The yellow hair on bumblebees covers most of their bodies, while carpenter bees sport yellow hair only on their upper part. Their lower part is solid black.
Like most things, the best defense is prevention. Seal crevices along your foundation and walls with caulk. Carpenter bees prefer unpainted wood in areas that get the morning sun. So, keeping up with deck maintenance is a deterrent, though oil or latex paint serves as a better restraint than deck stain.
Insecticides can help repel them from starting a new tunnel on the surface but it only lasts until the rain washes it off and won’t kill those in the galleries. That’s where insecticidal dust comes in which can be pumped into the tunnels.
Only plug the entry holes, which are about a half-inch in size, after all the bees are killed or in the early fall before the bees return to the gallery. (Using wood putty is best if you plan to paint.) If you plug the holes too soon, they’ll drill a new hole and you’ll have an explosion of sawdust as Lucia experienced.
As you would guess I’m concerned about using chemicals. Even pyrethrins, a natural insecticide derived from chrysanthemums, are toxic to our important pollinators such as carpenter bees. Given the circumstances though, an organic approach is safer when applied properly during times when pollinators are not active –in the early morning or late evening. Besides, deterring them from tunneling into Lucia’s deck will encourage them to take up residence in downed trees or old logs where they belong. Garden Dilemmas? AskMaryStone@gmail.com
A side note: Lucia learned of a bee trap that resembles a carpenter bees’ nest. The manufacturer touts, “Once the bees start filling the trap, their pheromone will start attracting other carpenter bees.” Sounds promising. I wonder if the outcome will be like the Japanese beetle bag traps that invite the neighborhood of Japanese beetles to your garden. Call me skeptical. I invite you to click through to a previous column that explains why… titled A Jiffy Jar of Japanese Beetles.