The most common urban pest beetle problems are caused by anobiids (furniture beetles, deathwatch beetles) and lyctines (true powderpost beetles). Lyctines were known as lyctids until recently, when they were demoted to subfamily status in the family Bostrichidae. Anobiids and lyctines are commonly found in flooring, furniture and structural wood.
I find that many pest management professionals have difficulty analyzing infestations of these two beetle types — and, therefore, what to do about them. Common questions include:
1. What is it?
The beetles themselves are seldom found, because they are small and active mainly at night. Only the round exit holes and frass are the usual evidence of an infestation. Although lyctine exit holes tend to be smaller than those of anobiids, they overlap in size.
The frass consistency tells you immediately which group caused the problem. If you rub the frass between your thumb and forefinger, lyctine frass will be very fine and smooth, like talcum powder. Anobiid frass will feel gritty, with “lumps” in it. You can really impress a customer if you pick up frass, rub it and announce the cause of the problem. It is important to determine which group caused the problem, because solutions may be different.
2. Is it active?
If the customer just noticed the frass or exit holes, the infestation is most likely active. However, frass may fall from exit holes for years after insect activity has ceased. New frass is light in color. Old frass is darker than the wood it came from. This indicates the frass has aged, and the infestation probably is inactive.
Marking exit holes and then examining the area later can determine activity. If new holes appear, then it is active. This is where taking photos with a smartphone, which records the date it was taken, can be helpful.
3. Where did it come from?
Both anobiids and lyctines usually require a year to complete a life cycle. However, as the wood dries or ages, life cycles can be extended for another two to three years. Consumers often think about suing builders or suppliers of hardwood flooring, cabinets or furniture. Of course, the suppliers will argue that it wasn’t their fault.
If exit holes appear within the first year, you can be sure the wood was infested before it was placed in the home. If exit holes appear several years after being installed in the home, your job is not so easy.
If it is a lyctine infestation and the wood is finished with lacquer, paint or polyurethane, the infestation had to have occurred before the wood was sealed. Also note that lyctines lay eggs in the pores of wood. If the wood has a finish of some sort on it, lyctines cannot infest it because the pores are sealed.
If it is an anobiid infestation and the moisture content of the wood is below 14 percent, the infestation had to have begun before the wood dried because this group requires wood with more than 14 percent moisture content. “New” wood often has moisture content high enough for infestation to begin, but as it dries, there is no reinfestation.
Keep in mind that many new “hardwood” floors are engineered. This means they have a soft wood interior and a hardwood veneer on top. Lyctines can’t infest them because they are sealed — but anobiids can.
4. What can I do about such infestations?
The easiest way to discuss this is, in my opinion, by the artifact or substrate that is infested as follows:
- Furniture: Because the customer likely does not want more exit holes, fumigation is the best way to correct the problem.
- Cabinets: Frequently, cabinet doors are infested by lyctines. Because the doors are usually finished, lyctines can’t reinfest, so the problem will solve itself. However, removing the doors and fumigating them is an immediate solution. The “box” of such cabinets usually is made of softwood, and lyctines can’t infest it.
- Hardwood floors: These can be infested by both lyctines and anobiids. Lyctines can’t reinfest because the floors are sealed. Anobiids can’t reinfest because the wood usually is below 14 percent moisture content. Your options are to wait for the infestation to resolve itself, fumigate the house, or replace the flooring. Some have considered applying borates, but the finish must first be removed, which usually is not practical. Flooring problems can become contentious between suppliers and homeowners, so be careful of the conclusions you make.
- Structural wood in crawlspaces and attics: In modern structures, softwoods like pine or fir are used. Only anobiids can infest them. Permanent control can be achieved by drying out the wood with ventilation, moisture barriers, etc. Borates are also a solution for these problems.
Older structures may have hand-hewn hardwood beams, which can be infested by both anobiids and lyctines. However, such beams are usually heartwood (the densest part of the timber), which is highly resistant to beetle infestation. Only the edges of the beam are damaged. Therefore, no control is usually indicated as the infestation died out long ago. If there is any question about current beetle activity, though, borates are an option.
Bostrichids and borers
Beyond anobiids and lyctines, there are a few other non-termite, wood-destroying insects that a pest management professional might encounter. False powderpost beetles (bostrichids), for example, can be found in bamboo or rattan products.
Occasionally, cerambycids (round-headed borers, long-horned borers and sawyers) are associated with damage to wood. In any case, a cerambycid infestation had to have begun before the wood was milled and the infestation is no longer active. No control is necessary.
One cerambycid species is a particular problem, however: the old house borer (Hylotrupes bajulus). With a distribution from Maine to Florida, and west to Michigan and Texas, it has a voracious appetite for unfinished (and in some cases, finished) wood. Such infestations must be identified correctly and then dealt with using a variety of tools for control.
Dr. Doug Mampe, a 2003 PMP Hall of Famer, can be reached at email@example.com.