Wood Boring Beetle Dust

**Matt Fellman** · 11-19-2010, 09:55 PM

This one always throws me.... 1960s crawl space, no vapor barrier, water presence, minimal ventilation. I'm fully expecting to find wood beetle exit holes all over but all I can come up with is dust from beetles stuck to the beams.

I see this a couple times of year and always recommend correcting the obvious and further evaluation and treatment for bugs. I guess my question is, where does the dust come from?

My best guess is that it comes from the wood scraps, debris and leftover form boards but I'm really just speculating.....

Also, keep in mind this may be a regional thing.... damp, unventilated crawls in Oregon are a breeding ground for bugs..... particularly boring beetles. And this isn't an isolated thing. I found the exact same conditions beneath 4 apartment buildings yesterday.

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**John Kogel** · 11-19-2010, 10:46 PM

I blew the picture up a bit and I think I see water streaks and mud smears over the pale yellow dust? That beam looks like it's in great shape from here.

Could it just be dust from the planer mill? It is weird, but could be man made.
I don't doubt there are bugs in the crawls down your way. Dirt floors are taboo up here now. .

I found powder post beetles in a couple of joists one day. Then farther in, I saw streaks of sawdust on the poly vapor barrier under a couple of joists, older place. I thought I was seeing a massive beetle attack, but there were hardly any holes in those joists. Turned out the streaks of sawdust were from carpenter ants pushing frass past the edges of the insulation batts. So it was actually ants in the subfloor planks, not beetles in the joists.

**Steve Howell** · 11-21-2010, 09:33 PM

The dust looks like it is from a non-decay fungal growth that enjoys the same environment as so called "powder post beetles." Anobiid beetles are the typical wood boring beetles found in overly humid substructure crawlspaces in the west coast states, producing the bird-shot like emergence holes and fine powdered frass. Their frass feels a bit gritty when rubbed between your fingers.
Your recommendations will be to reduce the humidity level as well as suggesting possible chemical treatment.

**Benjamin Gromicko** · 11-22-2010, 09:36 AM

Originally Posted by Steve Howell

The dust looks like it is from a non-decay fungal growth that enjoys the same environment as so called "powder post beetles." Anobiid beetles are the typical wood boring beetles found in overly humid substructure crawlspaces in the west coast states, producing the bird-shot like emergence holes and fine powdered frass. Their frass feels a bit gritty when rubbed between your fingers.
Your recommendations will be to reduce the humidity level as well as suggesting possible chemical treatment.

I agree. From the blurred picture... It could actually be indications of mold/fungal growth.

Ken Bates · 11-22-2010, 07:08 PM

I can think of some reasons how wood dust would get there but that won't solve anything.

If you had scraped away a small amount or just grabbed some with scotch tape you could look at the dust with an 8x or 10 x loupe (magnifying lens) and even identify the maker of the frass if that's what it is. Highly doubtful without exit holes. Each type of borer produces unique frass pellets that can be used for identification in the same way Botanists identify flora by pollen samples.

99% sure its not beetle frass.

**Don Hester** · 11-24-2010, 10:04 AM

Like stated above Anobiid tend to leave shot like exit holes and gritty frass. Did you sound or probe the wood to see if there was any degradation? I carry a rock hammer to test wood (dogs love me when I whack the woody, lol)

If there was no exit holes and no degradation it most likely fungus or wood dust from construction/manufacturing

It was hard to really tell from the pic.

**Matt Fellman** · 11-24-2010, 09:30 PM

I guess I should have said more in my OP.... I see this residue on wood dozens of times a year along with a bunch of exit holes and damage. Most times, I spot it within seconds of entering a crawl and go on to find widespread damage. Every once in awhile I see the EXACT same residue only no holes.... hence my question.

I'm doubtful of the manufacturing thing since the building is 40+ years old and I've never seen it on a dry, well ventilated crawl. It's just frustrating because I know there's been activity, I just can't find evidence.