QUESTION:

We were out to a customers house in March 2011 for holes in the dry wall. Nothing was found except holes about the size of the a tip of a pen, round, and all over her dry wall. No bugs were found and little to no frass was found. She had us come out again because there are more holes. We can not figure out what type of bug (if any) could be causing this. Let me know what you think. Thanks!

ANSWER:

We can skip the suspicions that these holes might be caused by someone maliciously walking around and punching them through the walls with a screwdriver, and assume that it is as you have said - the holes are appearing on their own. If this is the case then it would be an insect emerging through them from the wood inside, and my experience with lots of holes about this size has found the culprits to be wood wasps - horntail wasps in the family Siricidae. These are large non-stinging wasps that can be up to 2 inches long, from the tip of their nose to the end of the long ovipositor on the females, and they scare the heck out of homeowners when the wasps begin flying around inside the home. But, they will not reinfest anything in the home and at that point in the life of the wasp its only desire is to get OUT.

There should be at least some bit of evidence of something having chewed its way through the soft sheetrock - white dust on the floor below perhaps. The exit holes of these wasps are perfectly round and clearly chewed open, with no hanging chads or other evidence of something having been poked through it. With this many holes in this home there must be some of the wasps still inside, so inspect the window sills and other bright spots to see if they made their way to these potential escape routes. It also is possible that this could be from beetles, such as long horned wood boring beetles, but even here you should find the adult beetles in the home somewhere. You are in Pennsylvania, so I suppose it could even be Old House Borers which would have some potential to reinfest.

More commonly though, wood is salvaged from a dead tree and milled into 2x4's that are then used as studs in the walls. Ask if this home is less than 2 years old, and this could be another clue that it is from non-reinfesting wasps or beetles. If a tree is killed by fire or bark beetles it still may be cut down by logging companies and used for lumber, but before it gets cut down the adult wasps and beetles have found it and laid eggs in the bark. The larvae then burrow down and into the sound wood to feed, and often survive any treatments such as kiln drying. They then get built into the home and emerge a year or two later. To verify this you should try hard to find some adult insects. There is very little you can do to stop the emergence of these insects other than waiting for it to run its course. Except for the Old House Borer they will not reinfest, and once all the emerging is completed the holes can be filled with spackle or filler and painted over.

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