Carpenter Bees rarely cause structural damage to homes unless they have been drilling and nesting in the same wood for years at a time. More likely damage will happen when woodpeckers hear the Carpenter Bee larvae in the nests and then start to damage the wood in order to get at a tasty meal.
Treatment as related to Carpenter Bees usually means taking control of the nesting areas by eliminating the bees or using products to repel the bees.
When to treat: (1) It is a good idea to treat in the spring, when bees are first observed, (2) again in mid-summer to kill any bees which may not have acquired a sufficient treatment when they emerged, and a third time in early fall to contact any over-wintering bees occupying the tunnels.
Carpenter Bees like many other bees are very effective pollinators. Currently, there is a global shortage of pollinators which is threatening farmers’ livelihoods and our food supply. Due to this concern, please consider pesticide-free alternatives when treating Carpenter Bee nests.
Pesticide Free Treatment and Prevention
Carpenter Bees emerge in early Spring from their nests and start to collect pollen. On sunny, warm days, Carpenter Bees, both male and female, will leave the nesting holes. The females who are the active drillers will collect pollen to bring back to the nest, which will eventually feed the young. At this time, you can safely use a coat hanger to eliminate any larvae in the nesting site by inserting the wire into the nest and breaking up any larval activity. Coat the holes in almond oil or NBS 30. Once that is done plug the holes with a small ball of aluminum foil and caulk the holes with wood caulk or fill in the hole with a wooden dowel.
To further prevent Carpenter Bee nesting, spray NBS 30 Insect Repellent, a mix of plant oils that makes wood smell unpleasant to Carpenter Bees as well as drilling wasps and ladybugs. Apply the repellent after plugging the holes in early Spring. NBS 30 can be mixed with water for a temporary (30-60 day) topical solution or mixed with wood finish (always in the last coat applied) for a longer term repellent solution.
To provide alternative nesting options for Carpenter Bees, drill 1/2″ holes in wood blocks and hang them in sheltered areas around your house and deck. The bees will often decide to nest in these blocks, rather than trying to re-drill nests in the fascia and soffits of your home.
Pesticide Treatment and Prevention
Prevention may be accomplished by an insecticide additive like Bug Juice added to standard paint or log home finishes on new structures or when maintenance coats are needed and will eliminate bees.
Treatment as it relates to elimination of Carpenter bees which have already drilled into a structure, involves steps recommended by entomologists which are effective in reducing future nesting activities.
In early Spring, obtain a pesticide, product containing carbaryl (Sevin), cyfluthrin or resmethrin. Insert this in the nesting hole. Wait for the bees to exit the hole, then plug the hole with aluminum foil and either caulk the hole with wood caulk, or use a wooden dowel. Avoid inhaling the insecticide or contaminating your clothing with the spray. Always stand upwind from the surface you’re treating. Treated tunnels should be sealed with a small ball of aluminum foil and caulked with log caulk, wood putty or filled with a wooden dowel after 24-36 hours.
In conclusion, not everyone has the same level of issues with Carpenter Bees. Unfortunately, when even one hole is evident it should be treated with the full extent of treatment recommended for prevention. Treating one time and forgetting about it does not work! Monitor the situation from year to year in order to stay on top of the issue. An ounce of prevention………