PPDL Picture of the Week
June 7, 2021
Carpenter bees: What’s that buzzing around your
Elizabeth Barnes, Exotic Forest Pest Educator, Purdue University
Have you noticed large bees buzzing around your woodpile? Or
maybe near your porch? There’s a good chance you’ve encountered carpenter bees.
Carpenter bees are large, solitary bees that people often notice in the spring
when the bees build their nests. Female bees tunnel into wood using their
strong mandibles. The entrance holes to these tunnels are typically about ½
inch wide (about the size of your pinky finger) and perfectly round (Image 1).
Each tunnel is outfitted with several cells that the females will stuff with
pollen and lay a single egg in (Image 2). Once the eggs hatch, the larval bees
feed on the pollen until they are large enough to pupate and emerge as adults.
Carpenter bees only tunnel into
dead wood. If you find a perfectly round hole in a living or recently living
tree, you may have found evidence of the highly destructive invasive species
Asian longhorned beetle. If you think you’ve found evidence of this beetle, please report it!
How do I know if I’ve seen a carpenter bee?
are often confused with carpenter bees. The quickest way to tell them apart is
to look at their abdomen. Bumble bees typically have fuzzy abdomens (Image 3 a)
whereas carpenter bees have shiny, black abdomens (Image 3 b). If you’re still
unsure if you’ve seen a carpenter bee, we suggest trying out the iNaturalist app or website. This project can
help you to identify all sorts of organisms and your observation will be added
to an international biodiversity project. You can also send a specimen to
Purdue’s Plant and
Pest Diagnostic lab to be identified for a small fee.
Do they sting?
several large bees buzzing around your home can seem quite threatening but
these bees are mostly harmless. Male bees can seem aggressive but can’t sting.
Females can sting, but they rarely do so. In most cases, they will only sting
if held tightly in your hand or if you directly attack their nest. Male bees
can be distinguished from female bees by the yellow square on their face.
How much damage do they cause?
of damage that these bees cause varies widely between locations but, in most cases,
the damage is relatively minor. Carpenter bees like to re-use the same tunnels
year after year rather than building new ones. Once they’ve built a tunnel,
they are unlikely to expand it further. However, in some cases, they can cause
cosmetic or structural issues. The tunnels can also allow moisture to get into
the wood and cause further damage. In addition, woodpeckers occasionally
enlarge carpenter bees’ tunnels to eat the larvae inside.
How can I protect my property?
way to protect your property is to discourage the bees from nesting where you
don’t want them in the first place. Carpenter bees prefer unpainted, soft wood
and will generally avoid painted wood, pressure treated wood, and hard woods.
Taking preemptive measures like painting wood or using hardwood in construction
can discourage the bees from tunneling into areas you don’t want them. However,
this will not always guarantee protection. We have outlined further treatment
methods using a combination of insecticides and filling in the bee’s tunnels in
our bulletin on Carpenter
Do they have positive impacts?
bees, like many native solitary bees, are excellent and important pollinators.
If you have a garden or flowering tree, you might have these bees to thank for
some of your harvest!
Bees and Wasps: Carpenter Bee, Cicada Killer, and Mud Daubers
This article was originally in The Purdue Landscape Report Issue 21-07
Cover image by Jim Baker, North Carolina State University