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Wood Boring Beetles How do you know if you have an infestation of Wood Boring Beetles? You really cannot tell with a visual inspection of the wood. If there are holes in the wood, they have come from previous generations of exiting beetles. Once beetles exit, they may or may not re-infest the affected wood depending on the beetle species.
Wood boring beetles fall into two major categories, those that infest only live trees or recently harvested wood and those that infest dry, seasoned wood. For all practical purposes, it is not necessary to treat wood for beetles such as round head borers, flat head borers, ambrosia beetles, or bark beetles since they will not re-infest dead wood. However, emergence holes on exterior surfaces should be filled to prevent water from penetrating into the wood, causing decay.
Anobiid Beetles
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.
Treatments for anobiid beetles should always start with moisture control. Anobiid beetles prefer moist wood and high moisture levels shorten their life cycle and speed the development of the infestation.
The most effective chemical treatment is the application of borates. Borates make the wood toxic to the developing beetle larvae and prevent newly laid eggs from hatching. Usually it takes from two to three months to eliminate an anobiid beetle infestation.
Lyctid Beetles
The true powder-post or lyctid beetle attacks only hardwoods such as oak, ash, hickory, walnut, and mahogany. Infestations are most likely to occur in hardwood flooring and paneling. Other common infestation sites include bamboo furniture and trim and picture frames made from tropical hardwoods. Like anobiid beetles, the first sign of an infestation is usually fine talcum powder-like frass coming out of tiny round holes in the wood.
Another indicator is the presence of small, elongated black beetles on windowsills and other surfaces.
Lyctid beetles are typically introduced into a home as eggs or larvae in firewood or in new molding that has been improperly stored or dried. They have a relatively short life cycle and an infestation can spread to unpainted wood surfaces within a year or two. The female lays her eggs in the pores of the wood, so if these pores are filled with a paint or stain, the wood will not be susceptible to infestation.
Treating for lyctid beetles is similar to treating an anobiid beetle infestation. Lyctid beetles are particularly sensitive to borates. However, an infestation of lyctid beetles often becomes evident after the infested wood has been coated with a finish. For example, infested wood flooring may show no signs of an infestation until a year or so after it has been installed and finished.
In order to properly treat the floor with a borate it will be necessary to entirely remove the finish by coarse sanding. Once the floor has sanded and cleaned the borate (in this case we recommend Shell-Guard because of its penetrating ability) may be applied. Once dry, the floor may then be fine sanded and the finish reapplied.
Old House Borers
Old house borers present the greatest control challenge to the pest management professional. They are large insects with a life cycle that can extend to 10 or more years. The old house borer attacks only softwoods and the initial introduction typically occurs while lumber is being stored in a lumberyard. Although named the old house borer, the first emergence of these beetles in a home usually appears within five to seven years after construction.
The earliest indication of an old house borer infestation is usually the noise made by older larvae chewing in the wood. This can be very disconcerting to the homeowner, especially in the middle of the night when larvae are most active.
The appearance of oval emergence holes is the next step in the process. The frass consists of fine powder and small tightly packed pellets. Like an anobiid beetle infestation, most structural damage is caused by water infiltrating into exterior emergence holes, thus promoting decay.
Treating a home for old house borers takes some patience on the part of the homeowner. The only quick remedy is a structural fumigation. However, few homeowners are willing to bear the cost of a fumigation or the inconvenience of leaving their home for a few days.
Borate treatments work but they take time, sometimes lots of time before total control is achieved. It is not uncommon for old house borer activity to continue for up to a year and a half after a borate treatment.
Additional borate treatments will not speed the control process. Since older beetle larvae are large insects and at that stage of their lives eat little wood, their tolerance to borates is quite high. They will probably complete their life cycle and emerge as adult beetles.
The presence of borate in the wood does two things; first it kills younger beetle larvae that are feeding in the wood, and second it prevents any old house borer eggs from hatching. Thus, the borate treatment interrupts the beetle’s life cycle and eventually the infestation will end.
Best of all, a properly applied borate treatment is PERMANENT. As long as the exterior finish is properly maintained, the borates will remain in the wood doing their job for the life of your home.
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