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It's not enough to merely kill the adult bees or the reproducing females; you need to kill the bee larvae in their nests in order to keep them from reproducing. Apply insecticidal dust to the holes burrowed by the carpenter bees to ensure that larvae that are hatched will be killed.  Make sure you use dust to stop the reproduction cycle; other insecticides can become absorbed into the wood or wear off before the larvae are hatched. Do not seal up the hole when first applying the insecticide dust. This forces the carpenter bees to burrow new holes, meaning there's a chance they won't pass through the insecticide. After the bees have all been removed from existing burrows, seal the holes with plugs, puddy, or caulking compound to prevent their future use by other bees.  Make sure all the bees are dead before plugging the existing holes. Any carpenter bees that become trapped by the plugs will simply drill new tunnels into the wood around them. The best time to fill in these holes is in the fall months. Although carpenter bees can attack all wood surfaces, they tend to prefer untreated wood. Paint or stain with varnish any untreated wooden surfaces outside that may attract carpenter bees. Painted wood is slightly better at discouraging infestation than stained wood, but the difference is effectively marginal. The final step to preventing carpenter bee infestation is to spray insecticide on outdoor wooden surfaces that may attract carpenter bees. If you'd prefer not to use insecticide, hanging bee traps near wooden surfaces is also an effective deterrent.  Particularly vulnerable areas include underneath rail sidings, under decks, and around window sills. Untreated wood is especially vulnerable to infestation and should be treated with insecticide if it hasn't been painted or stained.
Use insecticidal dust to stop the cycle of reproduction. Plug the carpenter bee holes after all the bees have been killed. Stain or paint outdoor wooden surfaces to discourage bee infestation. Spray wooden surfaces with insecticide in the spring.