Carpenter bees can be killed using several effective methods, both chemical and natural:

• Insecticidal Dusts: Applying dust insecticides such as Tempo Dust, D-Fense Dust, or diatomaceous earth directly into carpenter bee holes is one of the fastest and most effective ways to kill both adult bees and larvae. Dust insecticides have a longer residual effect compared to liquids, and repeated applications in early spring and throughout the season help ensure control. After treatment, holes can be plugged to prevent re-infestation

• Residual Insecticide Sprays: Spraying residual insecticides containing active ingredients like lambda-cyhalothrin, zeta-cypermethrin, or pyrethroids (e.g., Cyzmic CS, Demon WP) on wood surfaces and into bee holes kills carpenter bees within minutes and provides protection for 2-3 months. Multiple treatments may be necessary for severe infestations

• Natural and Non-Toxic Options: Diatomaceous earth can kill carpenter bees by damaging their exoskeletons, though care must be taken to avoid inhalation. Boric acid diluted with water (3:1 ratio) sprayed into nests kills bees within about an hour. Essential oils like lemongrass and citronella act more as repellents than killers. Citrus juice mixtures may also deter carpenter bees but are less effective for killing

• Mechanical Methods: Bug zapper rackets deliver an electric shock to flying carpenter bees, killing them on contact, though this mainly affects males and does not eliminate nesting females

After killing carpenter bees, it is important to plug and seal the holes to prevent new bees from nesting in the same spots

. In summary, the most reliable ways to kill carpenter bees involve insecticidal dusts and residual insecticide sprays applied directly to nests and wood surfaces, supplemented by natural options like diatomaceous earth and boric acid for safer control