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Blooms benefit from carpenter, bumblebees
MISSISSIPPI STATE – Summertime brings out the flying and sometimes stinging insects in Mississippi, and some of them look a lot alike.
The mostly harmless carpenter bee resembles the sometimes bothersome bumble bee. Both are important pollinators in the Mississippi landscape.
Blake Layton, entomologist with the Mississippi State University Extension Service, said the look-alike carpenter bees and bumblebees are not even in the same entomological family.
“One of the most easily observed physical differences is that the top of the abdomen of carpenter bees is slick and shiny, while bumblebees are covered with black and white or yellow hairs,” Layton said. “Also, carpenter bees nest in above-ground wood galleries, while bumblebees nest in the ground.”
The Eastern carpenter bee is the most common species in Mississippi. They first appear most obviously in the spring when the males fly about energetically and the females bore nesting chambers, known as galleries, in wood. The next generation of carpenter bees emerges in late summer.
“The white-faced males are hard to miss because of their buzzing about, hovering in mid-air and occasionally in one’s face,” Layton said. “Some people feel threatened by this behavior, but the males are harmless because they have no sting. Females can sting, but they are not aggressive and do not sting unless forced to do so.”
Females are easily distinguished from males because their faces are solid black. Males have a distinct white spot in the middle of their faces.
Females bore nesting galleries in soft wood and divide these into individual brood cells, which they provision with pollen. Carpenter bees overwinter in the same brood galleries in which they developed.
“Galleries are a little less than 1/2-inch in diameter, can be a foot or more long and may contain 12 to 15 cells. Galleries are usually made in unpainted, softwood lumber,” Layton said. “They prefer pine, cypress and cedar, but will occasionally bore into other types of lumber.”
The carpenter bees do not eat the wood, but rather bore into it to create nesting spaces. Carpenter bees congregate, and bees will reuse and enlarge old galleries from year to year. In enough numbers, the galleries can weaken timbers, and their presence allows moisture to enter the wood, speeding decay.
“These are minor wood-boring pests, but their cumulative damage can become significant in some situations,” Layton said. “However, carpenter bees are important pollinators and should only be controlled when necessary to prevent structural damage.”
While some gardeners welcome carpenter bees by including split rail fencing in the garden, the best long-term way to keep carpenter bees away is to paint exposed wood surfaces. When painting to keep carpenter bees away, apply enough to cover the wood grain completely.
“Simply staining the wood does not usually work,” Layton said. “The bees will readily bore through paint as long as they can still feel the wood grain.”
Small amounts of insecticide dust can be applied directly into galleries to kill unwanted carpenter bees living there at the time and those that contact it months later. Choose an insecticide that contains deltamethrin or drione dust for carpenter bee control.
“Dust works better and lasts longer than liquid or aerosol treatments because it remains in the gallery, where it will contact the bees, rather than soaking into the wood,” Layton said. “Some gel or paste products with a syringe-like applicator are available so individual holes can be treated. But as long as there is attractive exposed wood, new bees will continue to appear.”
Bumblebees do not bore into wood like carpenter bees, but rather make their nests in the ground in burrows made by other animals such as field rats or moles. They sometimes nest in other ground-level, closed places such as in fallen, deserted birdhouses.
Richard Brown, director of the Mississippi Entomological Museum, said bumblebees can be very aggressive and will sting if their nest is threatened.
“They are docile when they are foraging on a flower, but if you look closely, you can tell if a bumblebee feels threatened when it is on a flower because it will lift one of its middle legs,” Brown said.
Despite their willingness to attack in defense of their homes, Brown said bumblebees are very important pollinators and should be protected.