The 400 sq-ft of flooring was ordered, delivered, installed, sanded and finished. Everyone was happy, you were paid and the check was deposited.  Ten months later the customer calls and reports, “Insect holes are appearing in my floor. The pest control operator was called out and says there are powder post beetles in my floor. The PCO advises me to fumigate the house. It’s going to cost around $10,000 and I expect you to pay, since it’s your wood that was infested.”

A false alarm, these galleries are grade characters. Note the galleries are at an angle and the interior walls are stained.

A similar false alarm with angled and stained galleries.

The 400 sq-ft of flooring was ordered, delivered, installed, sanded and finished. Everyone was happy, you were paid and the check was deposited.  Ten months later the customer calls and reports, “Insect holes are appearing in my floor. The pest control operator was called out and says there are powder post beetles in my floor. The PCO advises me to fumigate the house. It’s going to cost around $10,000 and I expect you to pay, since it’s your wood that was infested.” The consumer has been on the internet and has found where powder post beetle infestations can reduce wood to a powder. They relate the entire house is wood framed and most all the furniture is wood so the fumigation has to be done right away or the home will be destroyed.

Of course there are other wood destroying insects such as termites, carpenter ants, false powder post beetles, long horned beetles, etc. but the most common tech call about insects involves the true powder post beetles. Though there are only a few calls involving insects each year, the mere suspicion that insects are consuming the home elicits fear and very upset home owners.

Another false alarm; the gallery walls are stained and there is no packed dust.

The first response is to be concerned about the issue and listen to the consumer all the way through their explanation. Set up an appointment to look at the floor as soon as possible. This type of concern can’t be ignored. Suggest the consumer review the information on the NOFMA web site about powder post beetles. .

The first steps for dealing with any insect situation will be to determine if the infestation is active. An active true powder post beetle (ppb) infestation, family Lyctidae, will exhibit a newly formed circular hole in the face of the flooring with a ¼” to ½” long connecting gallery that is vertical to the surface of the flooring. The hole can be very small from 1/32” to about 1/8” in diameter. A small mound of fine “wood dust” will surround the hole like a volcano.  This is an exit hole created by the adult beetle. As the adults exit they are drawn toward the light so placing a glass over the hole with a nearby light turned on particularly at night can capture the beetle. This capture is important since positive identification by a professional entomologist is necessary for choosing options of remediation.

An active infestation; the 4 galleries show dust just under the finish just before the adults exit.

It is important to determine if the infestation is active since small “worm holes” are considered allowable characters in any grade of NOFMA certified flooring. These holes can be created by a ppb or any number of insects that either do not infest the lumber below the fiber saturation point or are killed during the kiln drying process. Oak, ash and hickory/pecan are some of the species with an incidence of infestation. Mesquite sapwood, some exotic species and bamboo can contain a very high starch content making them a preferred food source. Maple and cherry with their small pores are not considered good egg laying sites.

I have inspected floors where existing worm holes were packed with dust during sanding and were not filled. The holes were revealed when the finish film broke from foot traffic and the packed dust either was pumped out of the hole or sifted further down. The existing gallery walls were stained with finish materials and the surrounding wood was discolored. Some galleries were at an angle to the face, and extend deep into the board or even completely through. In these cases there was no active infestation and the remedy was to either accept the holes or fill them with appropriate filler.

An adult exit hole and a hole showing just before exit of the adult.

When an active PPB infestation is confirmed by the entomologist, some general facts should be relayed to the consumer. Only the sapwood of porous hardwoods with sufficient starch content is infested. That excludes the heartwood and softwood species. In addition, as sapwood ages the starch breaks down and has less food value, so old sapwood is not a suitable food source. This excludes older furniture. The wood must also have pores that are large enough for egg laying. Finish also seals pores and where applied helps protect the wood by reducing sites for laying eggs. It is true that a sapwood board or the sapwood portion of a board can be infested and reduced to a powder but this will take time and depends on the environment, number of larvae, and the food value.

Topically applied house hold insecticides can be used to kill emerging adults to buy extended time to make informed decisions for remediation. The key item is that the house structure is not in danger like with a termite infestation and the damage from the insects progresses slowly.

The same view as above photo, showing exit hole size in 4” hickory plank.

Determining that the flooring was properly kiln dried is important since kiln drying to the NOFMA standard of 6% to 9% kills all stages of insect activity, the eggs, larvae, pupae, and adults. That is, check the moisture content and size. Pieces with excessive shrinkage and at normal moisture content indicate kiln drying was not appropriate and may not have killed all insects. Kiln drying, however, does not prevent an errant adult insect from laying eggs on a suitable exposed board.  Therefore, a flooring board can be infested any time after manufacture during handling and storage or installation. If the infestation occurred after manufacture it is likely that only a few boards are exposed and the condition is minor. Fumigation in such cases is unnecessary as Dr. Harold Bancroft an entomologist at the University of Memphis relates. He makes an analogy that it is like killing a fly with a 500lb bomb.

A damaged board has been removed. Note the larvae trails on the felt paper.

For the errant adult infestation 30 or so eggs can be deposited in the pores of a few boards. The beetle larvae progress at different rates and emerge at different times. This can create the impression the problem is extensive since numerous holes appear in each of a few boards. But, it is only in these preferred boards. One recommendation is to monitor and kill the adults as they emerge. If the environmental conditions are marginal the activity can cease and the infestation is over.  Another option is to remove the boards that show activity. This removes the preferred boards that were infested and the infestation is over. For a more extensive emergence, say 20 to 30 or more boards treating the flooring with a borax based insecticide targeting ppb’s will kill  the larvae and will permanently treat the wood. Timbor®, BoraCare®, and Shellguard®, are insecticides that target ppb’s. (Check with the manufacturer to confirm recommendations and proper use.) A few adults may emerge after treatment since they do not actually eat the treated wood, but all larvae will be killed.

Three exit holes in a sample board removed during active infestation. Holes are 1/32” +/- in diameter.

Establishing where the flooring was infested can be difficult. The insects have been found in all areas of the continental US and most regions around the world so infestation can occur most anywhere. The typical life cycle of the insect is around one year with adults emerging in the nearest spring or fall. With ideal conditions the cycle can be accelerated to about five months. For adverse conditions, emergence has been reported as long as three or four years after installation. If the flooring is not properly kiln dried with the associated sterilization procedure and insects emerge, the responsibility often rests with the manufacturer.  However, the time line and the chain of custody point to the most at risk location of infestation. The longer a product remains exposed during storage the more at risk the product is for infestation. Old inventory should be avoided along with packaging materials that are not properly kiln dried. If flooring is exposed for long periods at a job site with the typical associated high moisture job site conditions, infestation at the site can be a possibility.

The culprit: a powder post beetle about 1/8” long. This insect produced one of the holes in previous photo.

The best action with insect infestation is to address it promptly and be open and straight forward with the consumer. As a contractor promptly inform your distributor and the manufacturer involved. ID the insect through a professional entomologist. If ppb infestation is confirmed discuss the options for remediation and act on the decision. Burying your head in the sand and blaming every one else does not remedy the situation. And remember, NOFMA Certified flooring is warranted to be properly kiln dried and   free of wood destroying insects when shipped from the manufacturer. If you have an incidence of insect emergence a NOFMA inspection can support common sense remediation.