QUESTION:

I have a log home that has some sort of reinfesting beetle. The exit holes are 1/16th inch in diameter and round, and appear for the most part on the exterior in various places on all sides of the home. This problem has gone on for several years. The house has a stain finish on the outside and a urethane finish on the inside. It seems that with both sides of the wood having a finish the beetles would emerge but not reinfest becuase of the finish on the wood. Am I wrong in thinking this? If I need to use a product such as Bora-Care to prevent reinfestaion, according to the label the wood needs to have no finish on it. What do you think I can do for this customer?

ANSWER:

There may not be an easy answer to this one. First, surface coverings such as paint, varnish, or stain could be "deterrents" to wood infesting insects, but they are not perfect barriers. This is particularly true of some of the small beetles that reinfest structural wood, as the female deposits her eggs either by inserting her ovipositor into tiny cracks and gaps in the wood or by crawling down into old exit holes. In either case that surface covering is bypassed. Your description of the size of these holes suggests it could be one of the "false" powderpost beetles such as deathwatch or furniture beetle in the family Anobiidae, or even perhaps a small species in the Bostrichidae. Since the holes continue to appear now, years after the home was constructed, it should rule out something that was built in with the construction, so we could assume this is a potential re-infesting species.

I happened to have the opportunity just now to speak directly with an excellent representative of Nisus, and asked him about the use of BoraCare over even just a stain. He said that a stain alone is a barrier to the borate penetration, so either stain or clear finish prevents the use of the borate. What would have to be done to use BoraCare, which probably is the best product for getting penetration deeply into the wood, is to sand the wood on the outside down to bare wood. Then the BoraCare can be applied and by label directions a new finish applied over it at the appropriate time.

As far as I know, the only other treatment that would provide penetration into the wood deeply enough to kill larvae on the inside would be a fumigation using Vikane, and the cost to the homeowner can be quite high for this. Another consideration with fumigation is that it leaves ZERO protection for the future, so if there is a presence of these beetles in this area it would be possible that they could begin a new problem even if all the current infestation is eliminated. That is the benefit of using borates - they last for many years to prevent future problems.

It may be possible to use other insecticides that are labeled for these kinds of wood infesting beetles, but they would be surface applications only, and would affect only the adult insects as they exit the wood, or perhaps as the females attempt to oviposit back on the wood. Since these would be synthetic active ingredients it could mean multiple applications over the season that the adult beetles are active, and for several years to ensure you affect any emerging later. This might be one of those awful decisions that paying the price to do it right the first time (sand, BoraCare, reapply the finish) would be the better thing in the long run.

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