Wood Destroying Insects
What Do Wood Destroying Insects Look Like?
The majority of wood-destroying insects are beetles, but other types of insects may consume wood for food, or damage wood when building a nest. Identification of wood-destroying insects is easiest with an actual specimen, but these are rarely available for beetles infesting wood. Therefore, we can learn by examining the size and shape of the exit holes, the texture of sawdust or frass (insect poop) that is left behind, and the type of wood that is infested. For example, is it a hardwood or softwood; new or old?
An important consideration when dealing with potential wood destroying insects is that not all damage represents a new or current infestation. Some wood can have old exit holes, while other pieces of wood can have holes that were internal galleries created before the wood was cut open at the time of milling. These can be confusing for homeowners that notice holes for the first time, even though they were present all along. New damage from wood destroying insects generally includes frass or sawdust, and the inside of the hole is a lighter color than wood that has been exposed to air.
A powder post beetle, Ptilinus ruficornis.
Painting surfaces can determine if wood-boring beetle damage is new. Old holes are painted over, making the new opening and sawdust obvious.
Left: Male carpenter bee; Right: Female carpenter bee
Female carpenter bees excavate long tunnels into wood, but only circular holes are visible. Woodpeckers drilling into eat the bee larvae expose the hidden tunnels.
Carpenter ants are structural pests that nest in rotten or damaged wood which can lead to structural problems.
Winged termites are the reproductive caste that leave the nest, mate and form a new colony.
Subterranean termites make tubes from soil particles, saliva and feces.
A swarm of Eastern subterranean termites. Photo: Curtis Wegener, Urban Pest Control of NY, Inc.
Should I Worry About Wood Destroying Insects?
Longhorned beetle larvae damage inside wood.
Wood destroying insects are a problem when they compromise the structural integrity of wood, especially if damage is not recognized for several years and populations are high. Damaged wood can also create opportunities for other pests to become a problem. For example, carpenter ants will invade wood previously damaged by termites, and carpenter bee populations can attract woodpeckers that further damage wood to feed on bee larvae. Insects accidentally brought indoors, on firewood for example, might be able to infest wooden items in the home if they are not protected by paint, polyurethane or other finishes.
Why Do I Have Wood Destroying Insects?
Wood destroying beetles
Wood destroying beetles can enter the home in a few different ways.
Building materials not properly treated prior to purchase
Wood flooring, structural supports, decorative wood pieces (mantle pieces, disks/coasters, tabletops, etc.)
Infested either as raw materials or during storage and shipment
- Firewood should not be stored near the house.
- If brought indoors and not burned in a timely fashion.
From other parts of the home
Moist crawl spaces, basements or attics with improper ventilation and exposed beams can become infested. Insects can move into the living space from these other parts of the home.
Some insects are attracted to wood for other reasons.
Females chew round holes, but woodpeckers seeking larvae open the galleries creating even more damage.
Attracted to exposed wood (not painted) on exterior portions of a building. This can include overhangs, fascia, window frames and sills, decks and wood siding and even fences. Carpenter bees do not eat wood. Instead they bore into the wood for nesting, and will use the same site over multiple generations. Female offspring may return to the same place they were born to lengthen a tunnel or create new burrows. Repeated nesting over time can lead to structural damage.
This is made worse by woodpeckers that dig into wood attempting to feed on developing bee larvae.
Carpenter ants indicate a moisture problem because they nest in wood weakened by moisture. The solution to most carpenter ant problems is to first identify the location of the nest, address the moisture problem that makes the site appealing to ants, and treat the ants.
In structures, most ant nests are satellite nests, meaning that the primary nest is located somewhere else – typically in a downed log or decaying tree or stump.
Subterranean termites make tubes from soil particles, saliva and feces.
Subterranean termites are the primary termite pest in the northeast. Termite workers, the group that feeds on wood, have a high moisture requirement, forcing them to stay in contact with soil moisture. Therefore, termites must feed on wood in direct contact with the soil, or create mud tubes to connect the soil to suitable wood. As a result, most problems originate in areas where the home contacts the soil: beams, pillars or other structural supports. If these are constructed of wood, then termites can directly infest them. If they are metal, stone or any other type of material, termite tubes will be needed to access the structural wood above. Tubes can be hidden inside support structures such as concrete hollow block and hollow metal supports.
This beetle feeds on moist, buried wood. The name “wharf borer” identifies a common food source: buried wharf piers. However, other wooden construction materials, as well as natural wood, buried in the soil can serve as food for these insects.
How Do I Manage Wood Destroying Insects?
Treatment of wood-destroying insects depends on what pest you have and what type of wood is infested.
Wood Boring Beetles
Larvae of these pests may be located deep inside wood, which is difficult to treat with standard insecticides. Therefore, a professional treatment by a certified pesticide applicator is almost always needed to control wood destroying insects. These treatments can include heat treatments or chemical fumigation that penetrate deep inside the wood to kill insects. Topical treatments with borate products can provide some relief, but only for certain insects that remain near the surface of the wood.
Pest management professionals successfully use dust insecticides to treat each carpenter bee tunnel. The advantage of this treatment is that the products remain active for long periods of time if they stay dry. This can treat multiple generations of bees that attempt to nest in the same location.
An alternative to insecticide treatments may be the use of traps. Preliminary work by the NYS IPM Program shows that traps catch both male and female carpenter bees, but also catch a number of non-target insects that may be considered beneficial.
Another approach that might work to reduce carpenter bee numbers is exclusion to seal current nest openings. More research is needed to determine if this treatment is effective alone or in conjunction with other treatments such as trapping.
Eliminating the moisture problem and treating the nest are critical. Treatment of satellite nests in homes can include physical removal with a vacuum cleaner, or chemical treatment with baits or sprays.
Treatment of these beetles is a challenge due to the breeding site location. Often underground and buried, it is not possible to access and treat the wood that harbors these beetles, and pesticide options are limited due to treatment instructions on the pesticide label. When wharf borers appear in a new location, often the best solution is to reduce their numbers with light traps and prevent their emergence with exclusion. The goal with exclusion is to seal openings where wharf borers can enter the room from the soil below.