By Brett Miller, NWFA Vice President Technical Standards, Training & Certification
It does not happen all that often, but there are a variety of insects that can infest wood products and either damage or completely destroy the wood. The most common types of insects that can infest wood floors include powderpost beetles and termites.
Almost all wood flooring is kiln-dried. Properly kiln-dried lumber will kill any insects and larvae present in the wood. Wormholes that are visible on the face of wood products, that were present at installation, also can be from pinworms, shot worms, grub worms, flag worms or other wood-boring insects that were in the living tree, but are no longer present or alive and do not represent an active infestation. These wormholes are acceptable within many wood flooring grades and should not be cause for concern. Damage caused by powderpost beetles and termites will require repairs.
Powderpost Beetles (Lyctid/Anobiid Beetles)
Identification
Powderpost beetles are the larvae of wood-eating insects that bore into the wood and feed on the wood fibers, causing damage. They can infest both hardwoods and softwoods. Properly kiln-dried lumber normally will eliminate powderpost beetles, but infestations can occur at any point after the kiln-drying process including during storage, transport or from contact with other wood products that are infested.
Infestation often occurs long before the wood flooring is installed, but also can occur after installation. This occurs when female beetles lay their eggs within the pores of bare, unfinished wood. The larvae feed on the wood, creating tunnels that fill with a powdery substance called frass. Later, when the larvae mature, they exit the wood, creating small pinholes generally measuring 1mm to 3mm (about 1/32” to 1/8”). In active infestations, the holes will be surrounded by this frass, which appears as a small mound of light-colored powder. This frass material is very fine and will feel like talcum powder when rubbed between two fingers. The presence of an actual beetle, beetle larvae or frass is the only way to absolutely confirm an active infestation.
Causes
- Improperly dried or stored lumber.
- Lyctid powderpost beetles usually are brought into the structure in wood products that contains eggs or larvae that may have been in furniture, firewood, untreated reclaimed lumber, joists or framing, moulding, trim, wood paneling, cabinets or even the pallets used to transport items into the structure.
- Anobiid powderpost beetles normally prefer to infest wood that is damp; therefore, infestations usually begin in moist, poorly ventilated areas such as in unconditioned crawl spaces or basements.
Cures
- Treatment should be conducted by a professional. The company should be licensed by the Department of Agriculture or other agency responsible for regulating powderpost beetle control in the state where the affected structure is located.
- As a surface treatment over raw wood, pesticidal formulations containing borate insecticide (disodium octaborate tetrahydrate) may be used by a pest management professional to treat structural wood.
- Removal and replacement of the affected wood.
- In the rare case of severe, widespread infestations when insects have spread into walls, between floors or in other areas where access or wood removal is impractical, structural fumigations may be necessary.
- Reduce and maintain moisture levels below 12% in and below the floor.
Termites
Identification
Termites are attracted to areas where moisture accumulates in and around the structure, including damp basements, laundry rooms, bathrooms and leaky foundation walls. They will eat any kind of wood including mulch, rotting wood, new wood, painted wood and treated wood. Stagnant, moist air in the structure provides the perfect breeding ground for termites. Termite-damaged wood usually is hollowed out along the grain, with bits of dried mud or soil lining the feeding paths. Wood damaged by moisture or other types of insects will not have this appearance. Typically, termite infestations are a site-specific condition.
Causes
- Improperly dried or stored lumber.
- Termites normally prefer to infest wood that is damp; therefore, infestations usually begin in moist, poorly ventilated areas such as in unconditioned crawl spaces or basements.
Cures
- Termite treatment should be conducted by a professional. The company should be licensed by the Department of Agriculture or other agency responsible for regulating termite control in the state where the affected structure is located. The treatment professional may use one of two general categories of termite treatment: liquids or
- Since termites require wood with high moisture content, correction of the moisture source is necessary.
- Structural damage should be repaired. Damaged flooring should be removed and replaced.
The National Wood Flooring Association has detailed information about wood-destroying insects available through NWFA University, an online training platform that is convenient and affordable. More information is available at nwfa.org/nwfa-university.aspx.
