Evicting Carpenter Bees

Q.Carpenter bees have taken up residence in my horse’s shed. I am trying to find the best way to get rid of the bees without harming my horse if he comes into contact with the insecticide used. The insecticides I have seen most effective against carpenter bees are Drione dust, Tempo 1% Dust, and Delta Dust. The labels say “for use around horse barns,” but then have a warning about coming into contact with animals. Are these products safe to use, or do you have any other suggestions?

—Jennifer Clarke, via email

A.Carpenter bees are important pollinators and do not aggressively defend their galleries, but the large bees are intimidating and, when abundant, can cause extensive structural damage. This can be compounded by woodpeckers that drill holes in the wood in search of carpenter bee larvae.

The weathered, slightly roughened surfaces of soft woods in barns and sheds provide ideal nesting sites for carpenter bees. Every spring, carpenter bees that have spent the winter in their tunnels emerge to expand established tunnels or begin to chew new ones, often nearby. These bees stock their tunnels with pollen as food for their developing larvae. Large aggregations of carpenter bees can accumulate in a structure over time.

Structures with exposed soft wood always attract carpenter bees, so management will be a continuous process. There are three major control options, which can be used singly or in combinations.

  1. When bees become active, treat entry holes by puffing a labeled insecticidal dust (such as those you mentioned) into the openings. Read and follow label directions and any precautions that must be taken when using these products around animals. Seal the holes with sections of dowel rod about two days after treatment.
  2. Try carpenter bee traps (various designs are available on the Internet). Put these out when the bees are first active and searching for nesting sites.
  3. Carpenter bees are very unlikely to attack slick, hard surfaces. Sanding and painting surfaces, though it’s not always pratical to do so, can deter these insects. Stains and preservatives, however, are less likely to be effective.