Expulsion of carpenter bees from horse stables – The horse

Q.Carpenter bees have settled in my horse stable. I am trying to find the best way to get rid of the bees without harming my horse if it comes in contact with the insecticide used. The insecticides that I have seen most effective against carpenter bees are Drione Dust, Tempo 1% Dust, and Delta Dust. The labels say “For use near horse stables,” but then warn against 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 drilling holes in the wood in search of carpenter bee larvae.

The weathered, slightly roughened surfaces of softwood in barns and stables offer ideal nesting places for carpenter bees. Every spring carpenter bees appear, who have spent the winter in their tunnels to expand existing tunnels or to chew new ones, often nearby. These bees fill their tunnels with pollen as food for their developing larvae. Over time, large clusters of carpenter bees can build up in a structure.

Structures with exposed softwood always attract carpenter bees, so management will be an ongoing process. There are three main control options that can be used individually or in combination.

  1. When bees become active, treat entry holes by blowing labeled insecticidal dust (like the one you mentioned) into the openings. Read and follow the directions on the label and all precautions that should be taken when using these products around animals. Seal the holes with sections of the dowel rod about two days after treatment.
  2. Try carpenter bee traps (different types are available on the internet). Lay these out when the bees are first active and looking for nesting sites.
  3. Carpenter bees are very unlikely to attack smooth, hard surfaces. Sanding and painting surfaces can put these insects off, although it’s not always practical. However, stains and preservatives are less effective.

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