Spraying is one of several methods for killing carpenter bees. The active ingredients and their concentrations determine how effective they are. Some sprays are more effective in certain situations. Sprays that persist in an area are more effective for containing existing infestations, while sprays that kill quickly are better for dealing with bees out in the open. The most effective method for removing carpenter bees is to kill them at their nesting site.
Carbyl is one of the primary ingredients in Sevin Dust. This pesticide comes in a powder form but can be mixed with water for spraying. To remove carpenter bee infestations from wood structures, spray liberal amounts of pesticide into the bee's nesting holes and then seal with putty or a cork.
Bifenthrin is the primary ingredient in bee sprays such as Spectracide. This spray is most effective when sprayed into the bee's nesting sites before sealing them. Bee nesting sites can be sealed with any material that isn't made of wood.
Cyfluthrin is the primary ingredient in the Bayer Advanced brand of bee killers. This spray is most effective against carpenter bee nesting sites. After spraying the nesting holes with cyfluthrin, seal the holes with caulk, wood putty or steel wool.
Deltamethrin is an ingredient in Spectracide, which comes in both sprayable and dust forms. Deltamethrin is used to kill carpenter bees in the nest. After spraying it into the bee's nests, seal them with caulk, putty or steel wool.
Only use insecticidal sprays in accordance with their labeling and with due caution. Insecticidal sprays are toxic, so avoid contact with them whenever possible.