Borate-Treating Freshly Sawn Wood

Ideas, thoughts, and tips for using borax and borate solutions to make green lumber bug-resistant. June 12, 2006

We are cutting a lot of mango wood here that is especially prone to attack by powderpost beetles. We'd like to use something less toxic than Malathion to initially treat the wood. I'm looking for a formula to make a borax / boric acid solution in the hopes that it will be less toxic to the applicators and environment, and will be more cost effective than available products. I am also looking for a source of supply for the borax, etc. I'd like to hear from anyone who might have tried this.

Forum Responses
(Sawing and Drying Forum)
From Gene Wengert, technical advisor, Sawing and Drying Forum :
Will the wood get rained on? If so, the borax will not stay in the wood but will leach out.
I am curious - do you have any concerns about the person using the wood still having Malathion chemicals in the wood and planer shavings?

From the original questioner:
No, we store it under tin or tents or in the shed. Yes, we are concerned about using Malathion at all points in the process. That's why we are looking at alternatives, before we get deeper into this. It is usually quite a long time till the wood is used, many months or years, and I understand that the active ingredient breaks down, but that patented smell is still there. It seems to plane off and be gone in the first layer - you can't smell it after initial planning. We haven't seen a reaction to mango that could be linked to the Malathion. Reactions that do happen seem to occur simply because of the wood itself. Some people are sensitive to it.

From contributor A:
Do a web search for Timbor. It is produced by US Borax located in California. My supplier was in Maryland. I have used it to kill powderpost beetles in sawn lumber and to act as a barrier after repairing termite damage. I'm told it as harmless to humans as table salt. It's in eye wash and Boraxo hand soap. I haven't used any wood treated with it but the company says it does not affect the wood's color or machining properties. It will leach out after repeated wetting. It is relatively inexpensive - a 25 lb bag that was as large as a 90 lb Portland cement bag cost a little over $100 with shipping. It yields about 25 gallons at 10% solution.

From Gene Wengert, technical advisor Sawing and Drying Forum:
It sounds to me like borax is a good choice for your situation. It will work indeed. Go to for more info. Note that borax is not designed to kill PPB in sawn lumber. First, the PPB is not in green wood, so it would not be used to kill PPB, but rather to prevent them from getting into the lumber. If the lumber is air-dried, then the borax will leach out and not do much good. If the wood is kiln dried, the heat will kill any PPB, so borax is not needed.

Second, if applied to dried wood, the borax is in a water solution and if applied to dried wood, will not penetrate very far into the wood, yet the PPB will often be quite deep. Wetting a dried wood like oak can increase the risk of serious checking and honeycomb.

From the original questioner:
We're just looking at prevention in fresh sawn wood. We've got 9 varieties here I'm told, and a particularly nasty one (false PPB) that leaves a rather large hole and will grind lumber into nothing. I kept poking around and found a website that offered a couple great formulas. It looks like I can make a Timbor-type product from bulk ingredients.

From contributor A:
The Wood Doc was correct when he said boric acid will not kill PP beetles in sawn lumber, but the statement can be misleading. The treatment does not go in very far, and will eventually leach out only if the wood becomes wet repeatedly, a problem for air dried wood that is exposed to driving rain. If not it will crystallize as the wood dries and remain as a barrier. As beetles emerge and eat the treated wood they will die. Any new larvae which emerge from newly laid eggs on the surface will die as they eat their way into the wood. Either way the life cycle is stopped effectively eliminating the infestation.

From contributor B:
Solubor is an unlisted, chemically similar form of DOT to Timbor, for soil boron amendment in tomatoes, peppers etc. We can get it at the farm supply. I've seen it listed in Forest Products Labs papers as the borate source. I've used it at about 1 lb per gal of hot water.

If you look up the MSDS's of Boracare, Shell Guard, you’ll see they use glycols to help maintain a wet edge, glycols dry slowly. They use variously, ethylene glycol (anti-freeze) propylene glycol (RV antifreeze) and PEG Polyethylene glycol. Somewhere in the FP Labs literature is a description of dipping fresh off the mill for 3 minutes and wrapping the tight stacked pile in poly for I think a week to let the borates diffuse in. Then sticker and dry as normal. I've read several anecdotes of the glycol mixtures reducing checking. I can only think that they might be lowering the drying stresses by keeping the surface bulked and drying slowly while the core dries normally, just a guess.

From Gene Wengert, technical advisor Sawing and Drying Forum:
The US Forest Products Lab did a study about the effects of polyethylene glycol dips on surface checking and found no benefit. Has anyone found any specific information about the safety (or lack of safety) in machining and sanding borate treated wood, and then breathing this dust? Is it OK to burn borate treated wood in a fireplace without any risk of unhealthy vapors?

Remeber that the larvae inside the wood can do a lot of damage before they exit, and borates applied to the surface (as described earlier) and not allowed to diffuse inward for weeks, will not affect the exisiting PPBs. The good news however is that the lyctid PPB does not like really wet wood. I wonder if constant sprinkling would control them in logs.

From contributor C:
By law we have to treat our specie that is susceptible to borers before it can be sold. We use borax in a vacuum chamber to impregnate the sapwood. I am not sure about the laws in the USA but in Australia we have to have a minimum retention rate in the sapwood to satisfy our laws

From contributor D:
Here in Maine you would need a pesticide applicators license and use approved pesticides according to their labels. Borax contains high levels of boron that if washed off a stickered pile of lumber may poison the immediate area. Interesting that Malathion is a quick acting pesticide and its toxicity disappears quickly, within a few hours. It may kill some pests in wood but a better bet, if fumigation is not needed, would be to use a repellent of which there are many on the market.

From the original questioner:
I thought that the borates were relatively inert. I had not thought of repellants. I'm looking for something that is relatively safe to handle. Our main problem is with the freshly sawn woods as the bugs don't bother it when the MC drops, so a repellant that would get us through the air dry phase would be great.

From contributor D:
Repellents are being used to a much greater extent in agriculture now. Many are considered organic and do not fall under pesticide laws. Some of those are garlic oil, lemon oil, hot pepper wax, etc. If you consider that pests are attracted to the scent of the new wood then anything that temporarily covers up that smell then becomes an effective block. Even though these aromatics are oils they are very light and do not penetrate the wood and stain or harm it in any way. They are highly volatile and last only a few days. Even spraying around the lumber stack or area might be effective. Insects react like people avoiding an area where a skunk has been. You can make your own from a cheap jar of chopped garlic which I do to spray on my garden and fruit trees. Borax is very good in the garden but it is just the slightest pinch needed to supply the boron used by plants. Many farmers and gardeners use just a pinch around cabbage family plants. More than that is asking for serious trouble. A teaspoon of it is enough for three years around a fruit tree!

From contributor E:
I found a recipe that worked great for me:
Bring a gallon of anti-freeze to boil (please don't sniff the fumes).

Add 2 lb. of Boric acid (roach powder).
Add box of 20 mule team borax.
Stir and dissolve all powder for say 30 min.
This stuff is best used on green lumber because of the “agrocisity” of the glycol in the antifreeze.
I actually add about a quart of water as it boils to help with dissolving.
I used red antifreeze and it actually left my SYP lumber with a warm (reddish) glow. Yes, green antifreeze left a greenish tint.
I used a paint roller to cover the wood (both sides).
I did this in a humid part of the country, air drying only freshly cut 1 x 6, 1 x 8, 1 x 10 of SYP, cut in the middle of summer, and the wood did not stain, the bugs stayed out, and I will use it again. A note on planing and finishing - as the Doc said, the vapors will not be good for you with this mixture either.

From contributor F:
I may be a little late reading this string as I live in Hawaii as well and have been dealing with all this rain. When I cut mango I treat it with Timbor that I get for about 8 dollars a 1# bag (makes 1 gallon at 10%) from Brewer Chemical here on Kauai. It seems to work well, but I do see that for the first week or two after the wood has been cut the PPBs still go after it, and do manage to get in the wood, but with no ongoing sawdust piles. The next batch I think I will try wrapping the wood in 6mil poly with a small dehumidifier so the bugs can not even get at the wood. There is someone over here who dries koa that way and it only takes about 6 weeks for a stack of 2" boards.