Preventing Insect Infestation in Lumber Production

Pesticides have limited usefulness and significant hazards. Good yard hygeine and application of heat are the more practical choices. February 14, 2006

I am cutting only softwoods - Western Hemlock, Douglas and Grand Fir, and maybe some Western Larch, into 1" boards. Do I need to worry about insect infestation? Should I spray it with Timbor, or something made for spraying on lumber products? I am stacking and stickering it to air dry, and will plane and edge it next year. Kilning is not an option. Any suggestions would be appreciated.

Forum Responses
(Sawing and Drying Forum)
From Dr. Gene Wengert, forum technical advisor:
Insect infestations are seldom a problem. Keep the yard area free of wood debris and you eliminate almost all the risk. Spraying the wood with an insecticide, even Timbor, only protects the outer layer of the wood, so any insects already inside are not controlled. Further, if you dry the wood aggressively, there is little risk. Of course, any insecticide you put on the wood will probably end up in the planer shavings and dust. Is this safe? Maybe you will wear a mask, wash your clothes and hands, etc., but maybe your customer will not. If you sell wood with an insecticide on it, do you need to legally provide the customer with a CIS and appropriate warnings? For many years (probably hundreds) commercial operations have not used insecticides for softwood lumber. Do you want to soak the wood in a product that will diffuse into the wood and so that the wood will contain this chemical for a long time?

Note that spraying the ground is only effective if the insects are out when you spray. Using a long-lasting insecticide is not safe, legal, environmentally responsible, or suggested. Always keep your lumber isolated from lumber sawn by someone else that may not be insect-free. This is especially true for any foreign lumber. There are fungicide and insecticide chemicals sold by several companies that are approved for lumber. They have a very short (30 days) life span, so they will safe when you get to processing the wood in a few months. However, if you are going to air dry for 6 months, you only have 1 month of protection and cannot reapply the products as they are all waterbased and you would be rewetting the wood.

From contributor A:
To Dr. Gene Wengert, forum technical advisor: Are logs for log homes that have been dipped in borate solutions safe to use, and does this process help to eliminate bug problems in the future? Could you give us some insight concerning commercial log home sales and proper treatment of the logs if any?

From Dr. Gene Wengert, forum technical advisor:
To contributor A: To be effective, borates must diffuse into the wood. This means that the borate solution (borates in water) must be in contact with the wood for a long time. Further, the wood must be fairly porous, so it would not work with white oak, heart maple, coastal Douglas-fir, wetwood hemlock, aspen, etc. A short dip will not allow the borates to penetrate into the wood deep enough and at a high enough concentration.

Borates remain water soluble, so that the logs, if they get rained on, will have the borates in these wet outer layers wash or leach out, and then provide no protection. Perhaps the best advice is to keep the logs dry, which means applying a water repellent finish to the outside and use appropriate construction techniques, including foundation ventilation, no shrubs against the walls, good roof overhang, etc.

From contributor B:
I'd recommend listening closely to what Dr. Wengert has to say on this. I needed short term protection for wood that I will be using myself and not selling. I have tried mint oil and pyretherins. Mint oil is the active ingredient in some sprays for ants and other bugs. I have bought it at some of the Big Box stores in aerosol cans. It smells good too. Pyretherins are harvested from flowers and break down in a matter of days to weeks depending on exposure to sunlight. Pyretherins can also make you sick so don't inhale it. There are synthetic versions of it too and the spelling is a little different. The synthetics are much stronger and don't break down as quickly and can make you really sick. The reason I mention this is that stores sell this stuff too for home use. The labels say they will kill PPBs and other wood boring insects. But remember, you are just treating the surface. The eggs are still in the wood and will hatch in the next year or two and then be in your home. Before you spray anything, just use the internet and search on a particular active ingredient before you treat anything, including your house. Some guys have had serious health problems from spraying things that they thought were safe.

My point is that you can find products that will deter wood boring insects without having to poison yourself. One idea I have is to try cedar oil but I'm not sure how well it will works or how to get it. Another idea that seems to be working is to surface the lumber. Some bugs like the rough surfaces and stay away from smooth surfaces. Believe it or not, it seems to be working. I have samples I am watching of boards cut from the same log lying next to each other. The bugs are going after rough one and leaving the other ones alone.

Anyone out there have anything they have tried? I'd like to know what worked and what didnít work.

From contributor C:
I've applied a solution yearly of cedarwood oil and neem oil in a distilled turpentine vehicle to totem poles. While this doesn't scare off the carpenter bees, we have never been bothered by PPB or carpenter ants. It even keeps off the paper wasps which like to pull off fibers for their nests. Cedar oil is avail through many chemical companies. What you are getting is probably made in China and is an extract from a juniper, like our ERC or aromatic cedar. I've also used boric acid applied with water and a roller as a vain attempt to forestall green stain in holly. It didn't work on the stain fungus, but insects hate it so it would probably deter any egglayers. I think as far as the beetles are concerned, good housekeeping is the key, and you should also keep an eye on the wood and look for frass (the dust that piles up outside a grub hole). If you find them, blast them quick with heat.

From Dr. Gene Wengert, forum technical advisor:
The lyctic PPB only affects hardwoods and mainly the grainy hardwoods like oak and ash. Are your totems softwoods? If so, that is why you do not see the lyctid PPB.