Ash, Pine, Bugs, and Borates

More info on the insects that may infest hardwoods and softwoods, and on the use of borate-based controls. December 6, 2009

I have a customer asking me to saw 2" ash from his logs for flooring in a post and beam barn (1200 sq ft upstairs and 1200 sq ft downstairs) he is intending to build on his property. He's using ash because that's what he's got. I am wondering how susceptible it will be to powder post beetles and whether anyone would advise against using ash for this purpose. It doesn't seem like kiln drying the lumber would be of any long term benefit for this use. Are powder post beetles indigenous everywhere or do some lucky persons escape them because of locale? (This is in CT where there are plenty of them.)

Forum Responses
(Sawing and Drying Forum)
From Professor Gene Wengert, forum technical advisor:
I share your concerns. I would also make sure that you tell your customer and have him sign a letter with those concerns so that you are protected in the future.

From contributor B:
Couldn't it be sprayed with Boracare or Timbor after it's down?

From the original questioner:
If not ash, what flooring would one use in a 2-story timber frame barn, built in the Northeast? Aren't red and white oak just as susceptible, and hickory too? What's left besides softwoods?

From contributor T:
I laid hemlock in the upstairs of my barn. Cut full 8/4, and as wide as possible. It has been down 10 years or more and is as good as new. I drive tractors, etc. on it. In our area it is one of the cheaper woods as well (Ontario, Canada).

From contributor D:
Solubor, available at the farm supply in 50 pound bags for about a buck a pound mixed at 1lb/gal water, will work. Chemically it's the same as Timbor. Dip it right off the saw for deepest penetration.

From contributor S:
I have red that birch, maple and softwoods are least likely to be attacked by wood boring insects.

From Professor Gene Wengert, forum technical advisor:
The PPB only infects hardwoods and prefers grainy hardwoods like oak and ash. Hemlock is a good choice. You can use one of the borate wood preservatives, but borate must cover all the surfaces and must penetrate, so you need to apply it soon after sawing (rather than after building) and then let it soak in for a week or so, so soak it or reapply every day - follow directions. Of course, it will not work on white oak very well as white oak is impervious to liquids. Borates are soluble in water so they cannot be used where the wood will get wet, such as from rain.

From contributor D:
They will infest maple, poplar, birch and I've even had them hit pine stickers on hardwoods lightly. If she thinks there is food there and if there are enough in the area they will try about anything.

Boracare is a glycol based borate. Glycols dry slowly so it can be used after construction, but best penetration, cheaper and with fewer chemicals is straight borate on green lumber.

Borates diffuse out of wood the same way they diffuse in - the cell has to be above FSP for it to mobilize. Casual wetting will not remove it in any significant quantity. A water repellant finish will prevent the wood surface from reaching fiber saturation point. I'm curious - can starch be removed or reduced from the cells in any economical way? Will ponding do it?

I took the picture below to show ram's horns, but the red maple is eaten up with PPBs.

Click here for higher quality, full size image

From Professor Gene Wengert, forum technical advisor:
The holes look too big to be the lyctid powderpost beetle. Its holes are 1/32 to 1/16" maximum. So, what you have in the picture is an anobiid beetle which is not active in dry wood (under 15% MC).

I repeat that lyctid PPBs do not infect softwoods, and that includes pine stickers. However, various anobiid beetles do.

Just to clarify, we do not use "straight" borate on wood to get preservative protection. Bora-Care contains 40% disodium octaborate tetrahydrate (not just "straight" borate) and 40% propylene glycol (not just glycol). Also, note that borate based preservatives are intended primarily to control termites, ants and roaches.

Timbor is a dry product that can be mixed with water to create a liquid borate wood spray or can be used in its original, dry form to dust wall voids and attics. When mixing for wood beetle or termite spray, use one pound of Timbor per gallon of water. This gallon of mixed borate solution will cover 200 square feet of wood. It is listed as controlling powderpost beetles. There is no glycol product in it.

From Professor Gene Wengert, forum technical advisor:
Correction: ethylene glycol.

From contributor D:
The trade names of the propylene glycol (RV antifreeze) based products are Shell-Guard and Boracol. Shell Guard also contains polyethylene glycol (PEG). Bora-care uses ethylene glycol (common antifreeze). The glycols simply dry slowly, so aid in deeper penetration in dry wood.

Sorry for the confusion - borate is a generic term for compounds containing boron and oxygen. All of the above products as well as Timbor and Solubor contain DOT, disodium octaborate tetrahydrate. By "straight" I meant Solubor or Timbor (DOT) mixed with water only for use on green lumber. Either of these can be mixed with any of the above glycols and used on dry wood. You can use the "straight" mix on dry wood but it doesn't penetrate as deeply.

The people at US Borax will send an info packet on borate preservatives and related research such as leaching tests, etc. You can also find articles on borate in the National Park Service Preservation Tech Notes.

DOT works on all PPBs, all wood consuming insects that I know of, decay fungi, and at high loadings it is also a fire retardant. It has low mammalian toxicity. Paint would also work as a barrier to egg laying.

From contributor F:
Doc Wengert, I too have bug problems with white pine any time I have lumber with wane with bark left on. Never happens till dry and in use (not kilned). It may take a couple years, but sooner or later you are going to start seeing sawdust under that bark spot and it never will stop till some day the piece of bark will be on the floor, pretty much powder on back side of bark. Just wondering if these critters are related.

From Professor Gene Wengert, forum technical advisor:
The best way to know what insect you have is to take a sample to your county extension office for ID. It is likely that you have the old house borer.