Diagnosing a Beetle Infestation

The Wood Doctor discusses the risk indicated by insect exit holes appearing in wood recently brought indoors. April 30, 2009

Question
I am seeing exit holes, about 1/16" in the end grain and surface (near the ends) of some air dried hard maple that is about 3-4 years old. It has been stored flat stacked indoors with three other species (red oak, white oak and cherry as well as with some nice KD curly maple.)

I see no evidence of exit holes in the three other species or the KD figured maple. I also don't see evidence of 'fresh' frass around the exit holes either. I sliced off an inch at a time from the ends of a couple damaged boards and the tunnels go very far in, (I quit at about 6") and are tightly packed with frass that appears yellow in color.

The lumber has all been piled together for over a year now. Previously the maple was piled with the white oak in my garage and the rest was stored in my detached shop. Does this sound like an active infestation? How can I tell for sure? I have a quantity of white pine with House Borer in it as well but it was easy to tell it had the infestation as OHB larva like to tunnel just below the bark that remains on some pine boards. PPB seem quite different.

Should I be very concerned with the other lumber (the KD figured maple, cherry and QS white oak in particular)? Is there much risk of beetles emerging from the wood going into winter? I'm in the process of moving all the stock to my new house (storing in the garage.)

What about danger of beetles infesting my house! My garage is insulated, with a vapor barrier and drywall. Is there danger of having all this wood (with house borers and potentially PPB) stored in there?

I’m currently working on the ability to heat treat the lumber to rid the infestations. If I store the lumber in the same room (garage) where it was prior to heat treat will the beetles likely be still present in my garage and re-infest?

Forum Responses
(Sawing and Drying Forum)
From Gene Wengert, forum technical advisor:
Exit occurs when the wood warms. The presence of frass is key to determining if the infestation is active. If active, then all the species you listed are at risk.


From the original questioner:

So bringing wood into a heated building will cause them to emerge? What about the storage area (attached garage) is the structure and the attached house at risk? How do I kill them in the garage area assuming they have not infiltrated the house yet?

If I don't see any further evidence of frass and there is no evidence of exit holes in the other species is it fair to assume the holes might have been ambrosia beetle and that they have run their course since the lumber is seasoned?


From Gene Wengert, forum technical advisor:
That is indeed more likely, but not 100%. Indeed, when you bring the wood into a warm environment, we will wee exit holes develop.

From the original questioner:
Is it likely that beetles leaving the wood if brought into a warm shop for instance will infest the building itself?

From Gene Wengert, forum technical advisor:
They prefer grainy hardwoods. The lyctid PPB does not go into softwoods. Most buildings are made of softwoods.

From the original questioner:
Thanks for the help Gene. I did a very close inspection of the wood pile where the contaminated maple was stored. They 'lived' together for over a year and there are no, not even one, exit holes in any of the oak, maple or cherry. When the affected maple was dry about 1-2 years I stacked some green white oak under it to dry as well for about two more years. None of the white oak shows signs of exit holes either.

I’m starting to feel more confident this was not PPB as I read in the archives that Ambrosia won't re-infest wood that's seasoned. It seems the exit holes are mostly in the end grain. I started cutting off 1" slices of one board to see if I could find larvae and stopped as the tunnels packed hard with frass were still going over 6-8" into the board. How far do they typically tunnel up into the wood?


From Gene Wengert, forum technical advisor:
Ambrosia does sound more likely. They can tunnel through and through.

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