To kill carpenter bees effectively, follow these key methods:
- Apply insecticides directly into the bee holes at dusk when bees are inside. Use residual insecticide sprays like Cyzmic CS, Demon WP, or FenvaStar EcoCap, which can last 2-3 months if protected from rain. Spray twice in spring at 3-4 week intervals for best results. For severe infestations, repeat treatments every two weeks and use insecticidal dusts such as Tempo Dust or D-Fense Dust inside all nests and holes to kill larvae and adults
- Use insecticidal dusts applied deep into the tunnels with a hand duster. Dust treatments are effective at eradicating existing infestations and preventing larvae development
- Non-chemical options include spraying a mixture of boric acid and water (3 parts water to 1 part boric acid) into the nest, which is toxic to carpenter bees
. Diatomaceous earth sprinkled inside the nest can also kill bees and larvae on contact
- Mechanical removal by vacuuming bees at dusk when they are inside the nest can reduce populations, especially if the nest is new and shallow
- After treatment, plug the holes with wood putty or caulk after waiting 24 hours to ensure all bees inside are killed. This prevents re-infestation, but plugging without insecticide may allow bees to reopen the hole
- Additional repellents such as citrus spray, almond oil, or essential oils like peppermint and eucalyptus can discourage bees from nesting but do not kill them
- Replacing or sealing wood surfaces with treated wood, paint, or polyurethane can prevent future infestations, as carpenter bees prefer untreated wood
In summary, the most effective way to kill carpenter bees is to apply insecticidal sprays or dust directly into their nests at dusk, follow up with plugging holes, and consider preventive measures like repellents and wood treatments to avoid future problems
