Keeping wood free of powder post beetles

[Cody Colston]

I'm thinking I need to treat the wood with a boric acid wash. Is it too late, if they have already bored into the wood?

I could be wrong but it's my understanding that treatment with a borate is a preventative, not a cure as it may not penetrate far enough to kill all the existing larvae. (those little holes and frass piles you see are the PPB's exiting the lumber after they mature) Heating the wood to 132 degrees at the core for a minimum of four hours is recommended for reliably killing an existing infestation. After heat treatment, then treat with a borate to prevent re-infestation.

[Scott T Smith]

I could be wrong but it's my understanding that treatment with a borate is a preventative, not a cure as it may not penetrate far enough to kill all the existing larvae. (those little holes and frass piles you see are the PPB's exiting the lumber after they mature) Heating the wood to 132 degrees at the core for a minimum of four hours is recommended for reliably killing an existing infestation. After heat treatment, then treat with a borate to prevent re-infestation.

Cody, the borate is both a preventative and it will also kill the larvae when they hatch and bore out of the wood. Heating is indeed the best way.

The problem with borate treating dry lumber is that the liquid causes the wood cells to expand, and then they will contract after drying - potentially causing surface checking. In some instances (such as a log cabin), you don't have many other options but in the case of furniture wood it is a solution, but not necessarily the best solution.

Yonak, you can build a home sterilization chamber and heat treat the boards yourself for not a lot of cost or hassle. There was an article in FWW a few years back that detailed the process. If you send me a PM with your e-mail address I'll be happy to send you the method.

[Cody Colston]

Scott,

I realize the topical treatment will kill the PPB's as they bore out of the wood but what about the eggs that they leave behind? Also, I believe that PPBs can incubate for years before hatching. How long do borate treatments last?

I treat my lumber with Timbor immediately after sawing, as I sticker and stack it. The lumber is already wet. Can additional wetting of the surface cause surface checking? I've not really noticed it if it can/does.

[Scott T Smith]

Scott,

I realize the topical treatment will kill the PPB's as they bore out of the wood but what about the eggs that they leave behind? Also, I believe that PPBs can incubate for years before hatching. How long do borate treatments last?

I treat my lumber with Timbor immediately after sawing, as I sticker and stack it. The lumber is already wet. Can additional wetting of the surface cause surface checking? I've not really noticed it if it can/does.

The borate won't kill the eggs, but when the larvae hatches (1 - 2 year typical gestation cycle) they will ingest the borate as they bore out of the lumber, killing them and ending the cycle. Unfortunately sometimes they stay inside the wood for several years before they bore to the surface, which is one of the reasons why heat is the best method for PPB treatment. Heat kills everything - eggs, larvae, and adult beetles.

Unless exposed to water, borate treatments will stay in the lumber basically forever (however there is a caveat to this which I will explain in the next paragraph). They can leach out if they are in a stack of lumber that is stored outdoors (or in outdoor furniture), or on posts, RR ties, fence rails, etc that are exposed to rain.

Applying Timbor immediately after sawing is the best application method because the moisture already existing in the lumber helps to wick the borate solution deeper into the wood. It's best if you keep the surface saturated for 10 minutes or so to encourage maximum absorption. Depth of penetration is important since it's the residual effect that you're after. When you spray dry, rough sawn lumber the treatment probably won't go much deeper than 1/16". Unfortunately (and this is the caveat), typically at least 1/8" is planed off of each side of a rough sawn board, effectively removing all of the residual borate treatment and reducing the effectiveness of treatment. Lumber treated green has a deeper penetration rate.

Additional wetting of the lumber can definitely cause surface checking. This is easily observed if you stack and sticker a pile of lumber outdoors w/o cover. Over time you will notice that the upper layer becomes highly surface checked, but the layers underneath are much less so. This is because of rain rewetting the upper layer boards after they have started to dry.

There is an entire chapter in the FPL Air Drying of Lumber manual that addresses decay, including surface checks due to rewetting. The amount of checking is directly proportional to the amount of water absorbed by the lumber.

[Allan Speers]

The borate won't kill the eggs, but when the larvae hatches (1 - 2 year typical gestation cycle) they will ingest the borate as they bore out of the lumber, killing them and ending the cycle. .

End the cycle? Who cares? What you want to end is the life of the eggs & larvae currently inside your wood. They can stay in there for up to (IIRC) FIVE YEARS, during which time they do massive damage. Do you really want to wait until they emerge to kill them?


Bora Care goes fully into the lumber, due to its glycol content, thus killing everything within a day or so. It also is much less prone to leeching out, again due to the glycol's ability to actually penetrate the wood cells. Bora Care costs more, and it's harder to make at home, but it's kind of a no-brainer for already-exposed lumber.

[Kevin Guarnotta]

Thanks for all the tips. It sounds like that fumigation method is the simplest, and probably cheapest method. I just wonder if it gets deep enough into the wood. It sounds like the Bora Care shjould fully penetrate into the wood. What happens when you plane that stuff? Does it put some toxins in the air?
Will I need to unstack my whole pile to apply the bora care to each individual board, or can I just reach in between the stickers with a pump sprayer?

This is such a bummer - with all the research I did into turning the tree in my yard into lumber, having a portable mill come to my house, and stickering it properly - I never thought about an infestation. I have two rather large piles of wood. I have just started to use it more and more. I actually just finished a dining room table. Luckily I had pulled the wood for the table a while ago - and it had been sitting in my shop.

As for the heat treating - that sounds good, but I don't know if there are any kilns around here, and I don't think I have the resources to move all that wood either. Heat treating myself sounds like it could be a good solution. I'll have to look into that option. I also keep honeybees - and their hives are not far from the piles of wood - maybe 50' away? I would worry about any chemical treatment nearby killing my bees.

[Allan Speers]

Thanks for all the tips. It sounds like that fumigation method is the simplest, and probably cheapest method. I just wonder if it gets deep enough into the wood. It sounds like the Bora Care shjould fully penetrate into the wood. What happens when you plane that stuff? Does it put some toxins in the air?
Will I need to unstack my whole pile to apply the bora care to each individual board, or can I just reach in between the stickers with a pump sprayer? .

I have never seen any "borate dust" per se in the air when milling, but if it is there (and it probably is) then it's mixed in with the fine sawdust, and you are going to avoid breathing THAT anyway. The main thing is, in my limited experience, I have not seen lumber treated with the glycol solution cause any problems with finishing.

Must you coat it all? I have no idea. It's certainly a good idea to spray from the top, not the sides, so that gravity helps, though I don't know for certain that this is necessary. Maybe you could just continuously spray from the top of the pile for a long time, figuring the solution will pass through each board & eventually get to the bottom ones? That would probably be very wasteful, though, and the stuff ' aint cheap.

I coated all of my boards on all surfaces, because I had a pretty large problem. (I lost several thousand BF !) What I did was skip plane all 4 surfaces, so I could look for holes and trails, then cut-away the obviously infected sections. THEN I sprayed it all down.

I needed to rebuild my stacks anyway, (Get tarps underneath, and design-in more air flow.) so for me this was a no-brainer.

[Scott T Smith]

End the cycle? Who cares? What you want to end is the life of the eggs & larvae currently inside your wood. They can stay in there for up to (IIRC) FIVE YEARS, during which time they do massive damage. Do you really want to wait until they emerge to kill them?

Allan,

I concur with you that a Bora Care type solution is the best method for treating already dry log cabin logs or timbers, etc that are not practical to place in a kiln, and I really enjoyed your posts about the homemade "boracare" solution and downloaded it for my records. It was extremely informative and well written. Thank you very much for putting that together and sharing it with us.

I think that you are misinterpreting my "explanation" to Cody as a "recommendation" though. Cody and I are both mill operators and work primarily with green lumber (which does not require glycol to wick the Timbor solution into the wood). Cody's post (which I was specifically answering) even references working with green lumber.

If you will go back and reread my posts you will discern that my preferred method of sterilizing lumber is heat. This is the only process approved by every lumber related sanctioning body. Timbor, Boracare, or any other boric acid or fumigation based method is not approved by every org, and as you know there are tradeoffs. I am not a supporter of rewetting already dry lumber, especially fine furniture lumber, due to the potential for surface checking to develop. I am also not a fan of using chemical solutions as the first choice when heat sterilization is well proven and leaves no toxic (or other type of) byproducts. Yes, chemical solutions do have their place.

I personally only use a 15% Timbor solution to treat freshly milled (green) thick slabs and timberframe timbers as an insect retardant during the air drying process. All slabs and most timbers are subsequently heat sterilized in one of my kilns after they have completed the air drying process.

Respectfully,

Scott

[Allan Speers]

Understood, Scott, and yes that all makes sense.

[Cody Colston]

Cody and I are both mill operators...

LOL, that's like saying a Boeing 747 Captain and an ultra-light operator are both pilots!

All, I have an entry-level, fully manual, band sawmill. I saw lumber for my own use, both woodworking and construction projects. I have a 300 bf capacity solar kiln for drying.

Scott saws primarily QS Oak, often in dimensions that my little 30 hp tractor wouldn't even lift. He runs a commercial operation, has equipment and capabilities that I can only dream about and has run a dry kiln for many years. If you can successfully dry Oak, you can dry anything. I certainly defer to him on any wood processing topics.

[Scott T Smith]

LOL, that's like saying a Boeing 747 Captain and an ultra-light operator are both pilots!

All, I have an entry-level, fully manual, band sawmill. I saw lumber for my own use, both woodworking and construction projects. I have a 300 bf capacity solar kiln for drying.

Scott saws primarily QS Oak, often in dimensions that my little 30 hp tractor wouldn't even lift. He runs a commercial operation, has equipment and capabilities that I can only dream about and has run a dry kiln for many years. If you can successfully dry Oak, you can dry anything. I certainly defer to him on any wood processing topics.

<grin> Thanks Cody, but I'm still learning too!

[Jim Andrew]

Says that they immersed the logs in the borate solution. That won't work for me. And putting the logs in a building after immersion will not either. Another thought, if you cut down an ash tree, saw it the same day, will the borers still be in the cambrium layer, so maybe if you cut the tree quickly enough, cut all the bark off, the wood might be clear of the borers. A guy could still spray some borate on the boards as you stack them, or maybe just put the tip of your sprayer in the gap between boards and spray away after you have the boards stickered and stacked.

[robert baccus]

Years ago I had a beautiful Magnavox steroe 8 years old start dribbling sawdust--guess what.