There are a number of small beetles that attack wood. Most attack wood that is alive (i.e., trees) or green lumber,) but a few will attack seasoned wood, like furniture, flooring, paneling, and stored lumber. Sapwood, the newly formed outer wood, is higher in nutrients and is attacked more frequently than heartwood.
Anobiid beetle damage is done by the larvae that feed and reduce the wood to a fine powder or mass of small pellets. Scientists call this debris frass. The larvae can tunnel in the wood for months or years before they emerge as adult beetles. Since the larvae never come to the surface, the damage can be considerable before it is noticed.
The most commonly encountered wood boring beetle infestation is caused by the anobiid beetle. Although often called a “powder-post” beetle, it is not a true a powder-post or lyctid beetle. One reason for its widespread presence is its ability to infest both hardwoods and softwoods. Since most modern construction uses spruce, pine, and fir softwood species, wood members such as floor joists, beams, sills, and studs are susceptible to attack by anobiid beetles. Most infestations start in crawl spaces or other moist areas then move to other sections of the home. Since most infestations develop rather slowly, damage is usually detected in homes older than ten years.
Fine sawdust or frass coming out of small holes in the wood is typically the first sign of the presence of anobiid beetles. The frass has a gritty feel to it as opposed to the talcum powder consistency of lyctid beetle frass. One of the challenges when dealing with an anobiid beetle infestation is the determination of whether the infestation is active or old. A good method is to cover a six-inch area of suspect wood with one layer of masking tape in early to late spring. If after a couple of weeks there are no small holes in the masking tape the chances are that the infestation is old and inactive.
Anobiid beetles have specific moisture requirements for survival. Since wood moisture levels below 13% (during spring and summer) are generally unsuitable for anobiid development/reinfestation, it’s advisable to install a moisture barrier in the crawl space of infested buildings. Covering the soil with 4-6 mil polyethylene reduces movement of moisture into the substructure and reduces the threat of an infestation spreading upwards into walls and upper portions of the building.
If the infestation appears to be localized (e.g., only a few holes in a board or sheet of paneling), simply replacing the board or sheet of paneling may solve the problem. If additional holes begin to appear in adjacent areas, additional action can then be taken.
Pesticidal formulations containing “borate” (boric acid) are especially effective against anobiid beetles in that they penetrate and kill beetles within wood, as well as those entering or exiting the wood surface.
For borates to penetrate wood, the surface must be unfinished. Therefore, joists, sills, rafters, subflooring, studs, decking, and siding are all excellent candidates for treatment. Although borates will not penetrate paint or varnish, they will penetrate wood surfaces previously treated with a water-repellent stain (e.g., wood siding, decks, or log homes), provided the water-repellency is broken down by pressure washing prior to treatment.
The two borate formulations currently registered for residual surface treatment of wood are Bora-Care® and Tim-Bor®. Both formulations are virtually nontoxic, odorless, and remain effective for as long as 40 years.
When applying borates or other liquid anobiid beetle surface treatments, it is important to consider that the application will only control infestations which are accessible, i.e., wood that is exposed and can be reached for treatment. Infestations which have spread into walls or between floors are candidates for more drastic measures such as fumigation.
Fumigation is an expensive means of ridding a structure of anobiid beetles and should be considered a last resort. However, in the case of severe, widespread infestations, it may be the only option. Instances where structural fumigations are warranted are when infestations have spread into walls, between floors, and other areas where access/wood removal is impractical. The best way to avoid such problems is through early detection and implementation of one or more of the corrective actions mentioned above.
Fumigation of infested furniture, antiques and other manufactured articles can be done at a substantially lower cost than fumigating an entire building by placing the items under tarps, in trailers, or in vaults that maintain gas concentrations at high levels.