Protecting Wood From Beetles

- Difficult to control but fairly easy to prevent -

Summary: Certain small wood boring beetles, called powderpost beetles, attack both hardwoods and softwoods. While it is relatively easy to prevent an infestation it can be very difficult to eliminate one once the infestation gets a foothold.

Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)

Borates protect wood from beetles

Borate insecticides such as Bora Care and Timbor are often the best choice when treating active infestations of wood boring beetles, and for preventing infestations from starting, see Borate Insecticides, Bora Care, and Timbor Insecticide for more information.

Borate insecticides are applied as liquids and form a layer of borate crystals in the wood's surface layer when they dry. Borate is toxic to insects, and fungi, and and thus prevent wood borers from crossing this layer either boring in or out. Borates applied to the surface of wood do not generally control larvae that are already in the wood at the time of application, however.

If you are installing hardwood flooring, for example, here's a suggestion: flooring material is sometimes infested with lyctid powderpost beetles when it arrives on the job site. Despite manufacturer's claims to the contrary, this can occur even if the flooring stock has been kiln-dried. Kiln-dried wood can become infested if stored improperly and exposed to an active beetle infestation.

powderpost beetle emergence holes

Anobiid powderpost beetle emergence holes in fir.

To stop a potential infestation treat the flooring stock with borate before installation. Borate solution should be applied to the unfinished back and tongue/groove edges. Solution can also be applied to the top if this surface is unfinished. Do not apply to finished surfaces because the borate solution must soak in to be effective. Borate solution can be mixed yourself and applied with a small brush or paint roller.

After the solution dries the wood will be impregnated with borate which will prevent beetle larvae from boring into the underside, or edges, once the floor is installed. The top side is protected by the finish applied to this surface. Don't get the wood too wet as the flooring may warp, and allow flooring to dry completely before installation. This procedure won't stop beetles already in the wood floor from emerging but it might stop, or slow, an infestation from growing.

Prevent structural wood damage

Infestations of anobiid powderpost beetles in structural wood like floor joists, wall studs and posts occur mainly in coastal, and other damp, climates where the wood has a relatively high moisture content. Damage can be extensive if left untreated. Weakened timbers should be replaced and remaining wood treated with borate insecticide.

Related Articles

What are Wood Boring Powderpost Beetles?

Powderpost Beetles Guide

anobiid powderpost beetle damage

Anobiid beetle damage in softwood. Damage (arrow) is concentrated near the surface in this side view.

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