Powder Post Beetles, Vol. 6, No. 6

Filed Under:

April 14, 2020

Lyctus spp.

Order: Coleoptera
Family: Bostrichidae

We had this floor installed last year and have really been enjoying it. Now some boards have these little brown beetles boring out of them; it started this spring. What are these and where did they come from? Will they continue damaging the floor or will they spread to other wood in the house? Powderpost beetles, a.k.a. lyctus beetles, occasionally occur in newly installed hardwood floors, as well as cabinets and other wooden items made from pecan, hickory, ash and oak, or bamboo. Females lay their eggs in the relatively large pores these woods possess, but they do not attack softwoods, such as pine or spruce, though there are other beetles that do. Because wood declines in suitability as it ages, powderpost beetle infestations are most common in wood less than 10 years old. Wood that is used in hardwood floors and furniture is usually kiln-dried before processing and the temperatures reached in this process kill any insects present. However, re-infestations of powderpost beetles can occur at any time after the wood is removed from the kiln and before the floor is installed and finished. This can occur when the wood or flooring is stacked at the production facility or while the flooring is being installed. Wood with a moisture content above 8 to 10% is much more vulnerable to attack.

Because wood declines in its suitability for larval development as it ages and as moisture content declines, minor infestations may be self-limiting and may not adversely affect the strength of the wood. On the other hand, heavy infestations, such as sometimes occur in wood with high moisture content, can cause such severe damage that floorboards will not support the weight of a chair leg and infested structural timbers will be greatly weakened.

Unless there are other hardwoods with unsealed/unfinished surfaces in the building, the potential for infestations of powderpost beetles to spread to other areas of a building is relatively low. This is because powderpost beetles do not attack softwoods and cannot lay eggs into hardwood surfaces that have been finished and sealed. Also, hardwoods become less susceptible to attack as they age and as moisture content declines. But infestations can and will spread to any other suitable wood in the building that has unfinished, exposed surfaces where females can lay eggs.

Control: Response to an infestation of powderpost beetles depends primarily on the severity of the infestation, along with other considerations. In many cases, doing nothing, other than getting and keeping moisture content low, keeping exposed wood surfaces sealed, and being willing to live with a few small holes in a few floorboards is an appropriate response. Treatment of heavier infestations may range from removing and replacing individual floorboards to removing and replacing the entire floor. See the article “Powderpost Beetles in Hardwood Floors” for more detailed information on how to deal with infestations of powderpost beetles. http://extension.msstate.edu/content/powderpost-beetles-hardwood-floors

Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service.
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