Question: Every spring, my deck becomes the battleground with bombarding carpenter bees. Please help?
Answer: Many people report being harassed by bumblebees flying under the eaves of their homes or picnic tables. How-ever, bumblebees are social in-sects and have their nests underground and spend most of their time traveling between the nest and the flowers. Carpenter bees resemble bumblebees but are not social insects and construct their nests in trees or frames of buildings. Homeowners not only complain about the antics of these bees but also the round holes bored into the wood trim.
Carpenter bees are large, 3/4 to 1 inch long, and have a blue-black to black colored body with a green or purplish metallic sheen. The upper body, or thorax, is covered in bright yellow, orange, or white hairs. The males have white markings and fly around aggressively. However, they are harmless and lack a stinger. Females have black heads and are docile and rarely sting.
Bumblebees have a fuzzy yellow abdomen as compared to the black shiny abdomen of carpenter bees. This distinction is important because even though both bees are pollinators, the bumblebee is not an economic pest as the carpenter bee can be.
Both male and female carpenter bees overwinter as adults in their old nest tunnels. In spring, usually April to early May, the adults emerge and mate. The females drill holes 3/4 of an inch in diameter into wood and lay their eggs.
To prevent infestations keep all exposed wood surfaces well painted. Wood stains do not prevent damage. Nail holes, ex-posed saw cuts and unpainted wood are attractive nesting sites. If an infestation occurs, you must treat each individual tunnel opening with an insecticide. During the daytime, locate the tunnel entrances, then after dark, on a cool evening, when the bees are less active, spray or dust the nest entrance. Dust applications are usually more effective than sprays.
Mature bees will emerge through the opening and come in contact with the dust. Treat in the spring when first observed, again in mid-summer and a third time in fall.
Later when adult activity has quieted down or even autumn, plug the tunnels with steel wool, caulk, wood putty or a dowel. If tunnels are plugged before bees are killed, they will chew new openings elsewhere.
The damage to the wood from a single carpenter bee is minimal but subsequent year infestations will expand the tunnels in branching patterns and may cause considerable structural damage.
Mona Bawgus is a certified master gardener and consumer horticulturist with Rutgers Cooperative Extension of Atlantic County. Write to her c/o Rutgers Cooperative Extension, 6260 Old Harding Highway, Mays Landing, NJ 08330. Email: firstname.lastname@example.org