carpenter bees - Ask Extension
Hi, Are there wildlife-friendly approaches to dealing with carpenter bee infestation in my window frames, or alternatives to chemical insecticide and ...
Knowledgebase
carpenter bees #916300
Asked September 03, 2025, 8:27 AM EDT
Hi, Are there wildlife-friendly approaches to dealing with carpenter bee infestation in my window frames, or alternatives to chemical insecticide and caulking their entrances? Thanks so much.
District of Columbia County District of Columbia
Expert Response
Hi Lizzy,
Sorry the carpenter bees have taken a liking to your house. There are some eco-friendly methods of dealing with carpenter bees, but depending on their current attachment to your windows, an insecticide or pesticide may be necessary at least once and then using friendlier methods to prevent future nests.
The University of Maryland recommends the best times to treat and repair damaged wood and minimize the killing of these pollinators would be late summer (after the summer emergence and before hibernation) or early spring before nest building begins. Carpenter bees are usually searching for nest sites in April-May.
Unfortunately most research suggests the most effective option for an infestation is to remove infested wood and replace it with new treated or painted wood or non-wood option.
If it is not that bad yet or replacement is not an option some resources suggest plugging the holes with steel wool and caulk or wooden dowels. Then paint the entire wood surface to deter new nesting. Some resources recommend treating the holes with a pesticide before caulking or any bees trapped inside will chew through the plugs and reemerge.
Most importantly, if the wood surface as a whole is not improved, bees may reinfest the same area. Try maintaining finished wood surfaces with fresh paint or stain because the bees prefer untreated wood or treated surfaces with cracks of nail holes where the can bypass the finishing.
https://extension.umd.edu/resource/carpenter-bees
Coating the wood with almond oil in the spring is another option to deter them from nesting there.
https://marylandgrows.umd.edu/2022/10/10/the-good-and-the-bad-of-carpenter-bees-can-we-get-along/
Crown Bees offers some additional suggestions at the link below, such as making a fake wasp nest (e.g., out of a paper bag), and windchimes for vibration and sound deterrent. They mention almond and citrus oil too and filling holes with steel wool and caulk. They also recommend putting an untreated wood post or old wood somewhere else for the bees to use instead of our homes.
https://crownbees.com/blogs/news/8-simple-ways-to-prevent-carpenter-bees-from-moving-in
If infestation is high or risk of damage to structural integrity is great, insecticides may be necessary. Treat tunnels in early spring before nesting activity has begun, or in late summer/fall after all bees have emerged. It doesn't work to treat active nests (those containing eggs, larvae, or pupae) in late spring to summer, since each brood chamber is sealed with partitions of wood particles at each end that wold block the chemical from reaching all of them. These baby bees can chew their way out after the pesticide loses efficacy. And please follow all instructions for use of any chemicals or call a professional pest management company if you are not comfortable treating the site yourself.
Please let us know if you have any more questions and good luck!
Hollis
UDC Master Gardener Volunteer
Sorry the carpenter bees have taken a liking to your house. There are some eco-friendly methods of dealing with carpenter bees, but depending on their current attachment to your windows, an insecticide or pesticide may be necessary at least once and then using friendlier methods to prevent future nests.
The University of Maryland recommends the best times to treat and repair damaged wood and minimize the killing of these pollinators would be late summer (after the summer emergence and before hibernation) or early spring before nest building begins. Carpenter bees are usually searching for nest sites in April-May.
Unfortunately most research suggests the most effective option for an infestation is to remove infested wood and replace it with new treated or painted wood or non-wood option.
If it is not that bad yet or replacement is not an option some resources suggest plugging the holes with steel wool and caulk or wooden dowels. Then paint the entire wood surface to deter new nesting. Some resources recommend treating the holes with a pesticide before caulking or any bees trapped inside will chew through the plugs and reemerge.
Most importantly, if the wood surface as a whole is not improved, bees may reinfest the same area. Try maintaining finished wood surfaces with fresh paint or stain because the bees prefer untreated wood or treated surfaces with cracks of nail holes where the can bypass the finishing.
https://extension.umd.edu/resource/carpenter-bees
Coating the wood with almond oil in the spring is another option to deter them from nesting there.
https://marylandgrows.umd.edu/2022/10/10/the-good-and-the-bad-of-carpenter-bees-can-we-get-along/
Crown Bees offers some additional suggestions at the link below, such as making a fake wasp nest (e.g., out of a paper bag), and windchimes for vibration and sound deterrent. They mention almond and citrus oil too and filling holes with steel wool and caulk. They also recommend putting an untreated wood post or old wood somewhere else for the bees to use instead of our homes.
https://crownbees.com/blogs/news/8-simple-ways-to-prevent-carpenter-bees-from-moving-in
If infestation is high or risk of damage to structural integrity is great, insecticides may be necessary. Treat tunnels in early spring before nesting activity has begun, or in late summer/fall after all bees have emerged. It doesn't work to treat active nests (those containing eggs, larvae, or pupae) in late spring to summer, since each brood chamber is sealed with partitions of wood particles at each end that wold block the chemical from reaching all of them. These baby bees can chew their way out after the pesticide loses efficacy. And please follow all instructions for use of any chemicals or call a professional pest management company if you are not comfortable treating the site yourself.
Please let us know if you have any more questions and good luck!
Hollis
UDC Master Gardener Volunteer
Thank you, Hollis! This is excellent. I have new strategies for the timing of my intervention and for limiting future infestations. I appreciate the guidance!
Keep us posted!
