Chemical Sprays for Controlling Mold on Green Lumber

By and large, chemical treatments are ineffective for preventing mold or bluestain. Quick drying is your best bet. March 31, 2008

I have several jobs coming up involving old pine logs. Mold was a real problem for me on some similar logs recently. Even with prompt (immediate) sticker stacking, the mold took over! What do you use and what does the concentrate cost?

Forum Responses
(Sawing and Drying Forum)
From contributor C:
I've never fooled around with spraying logs with anything, but Home Depot in the rental division carries a product called Concrombium that is a pretreatment for building materials that may work. It also works wonders in moldy basements and crawl spaces.

From Professor Gene Wengert, forum technical advisor:
Concorbium is the product mentioned. It can be used on dry lumber, but I could not find that it was approved or safe for use on green lumber. It may not work on green lumber either, as it is designed for dry products.

The concern with chemicals put on green lumber is that they will carry over. That is, that after drying they will still be in or on the lumber and therefore will be in the planer shavings and sawdust, and potentially in the wood itself that is used for baby cribs, toys, cutting boards, etc.

There are a few chemicals that are approved, such as NP-1, and these have very short lives. But because they are weak, most of these approved chemicals do not control mold, especially penicillum mold, which is common on green lumber. (I say "most" as I am not certain if there are any that will control mold.)

Mold control is achieved either by going directly to temperatures in excess of 130 F, or by immediate stacking (3/4" thick stickers) and drying at low RH and high air velocity.

Old logs present special problems as the blue stain fungus will already be deep within the wood. Chemicals do not control fungi that are within the wood. Although both are fungal in origin, blue stain and mold are quite different; mold is only on the surface while blue stain goes into the wood.

From contributor P:
The products which I have seen for stopping mold contain either Didecyl Dimethyl Ammonium Chloride, or a carbamate compound which has another long name (which is eluding me right this moment). Another component can be Dimethyl Benzyl Ammonium Chloride. Some products use these in combination with plant extracts or in combination with borates. The borates are intended to buffer the moldicides, making their effectiveness hang on a little longer, and add more fungal protection to boot.

From Professor Gene Wengert, forum technical advisor:
The popular chemical for sapstain is NP-1 and it contains:
Didecyl dimethyl ammonium chloride
3-iodo-2-propynyl butyl carbamate.

Neither of these is extremely effective for controlling wood mold in drying. The reason is that the mold is not eating stuff in the wood which contains the poison. Rather, the mold is merely using the wood as a damp substrate to grow on. So, forget about mold control. (I have seen less mold occurring with Busan 1009 than with other chemicals; this is an observation and not the results of a test.)

Other approved wood dips include
Copper 8-quinolinoleate
Methylene bis (thiocyanate)

For those not familiar with chemical dips, you do need a stainless steel tank. Spraying is not acceptable as the chemical ends up everywhere. You also must keep a chemical log (employee's name, chemical concentration, volume of wood treated and so on for each shift). You also must lift the bundle of lumber out of the treating solution and let the excess drip off back into the tank. These are just a few items that must be attended to when using these fungicides and insecticides. Because we do not sell the wood as having been treated, we do not need a license to apply. Nevertheless, it would be prudent to attend a pesticide class to learn how to handle these chemicals safely.

From Professor Gene Wengert, forum technical advisor:
TCMTB is another approved chemical. It got lost in my previous posting.