The examination of the home for evidence of wood-destroying insects and wood-destroying fungi (rot) is an important aspect of a complete home inspection, and   WARREN HOME INSPECTION COMPANY is fully licensed by the Oregon Department of Agriculture to perform this service.  We do not charge an additional fee for this inspection, however a stand-alone WDI/WDO inspection is available.   Some mortgage lenders (including FHA, VA and some conventional sources) require an NPCA-1 form which attests to the presence or absence of infestation, rot, or "conditions conducive" to either.   We will provide this report, and will also discuss any findings with the lender at the request of the client.

There are many invasive organisms and insects that do not present a meaningful problem in our area.  We describe below the primary culprits in the Northwest.   Topics included in this summary are:   Wood Destroying Fungi, Carpenter Ants, Wood Boring Beetles, Subterranean Termites, and Dampwood Termites. 

For additional information, check out the links related to pest control on our Resources & Links page.

Wood destroying fungi, commonly misnamed "dryrot" (since it takes moisture to cause the fungi to grow), is the only wood destroying pest in our part of the world that is plant life and not animal. Yet, wood destroying fungi is the most structurally destructive pest of all organisms that we are confronted with. Each year, over $17 billion worth of damage is caused by fungi rot in the United States. In western Oregon and Washington, fungi rot causes more damage than all other pests combined.

Four major categories of wood destroying fungi affect structures in the Pacific Northwest:

Brown rot: Generally the most common. Damage appears darker than the surrounding wood, with cracks across the grain, appearing cubical in shape. Damage often progresses from the interior of the wood member out toward the surface

Soft rot: Similar in nature to brown rot except that damage is not as accelerated, damage progresses from the surface inward

White rot: Leaves a bleached appearance, requires a higher moisture content than brown rot in the wood to survive, damage often progresses from the surface inward

Poria incrassata: Water-conducting fungi, needs a source of moisture (wet ground contact, plumbing or roof leak, etc.) to become established, damage can be greater in sound wood some distance from the moisture source. This pathogen spreads very rapidly and damage can occur in a matter of weeks or months from the initial establishment of the fungi.

Corrective measures: Control of any wood destroying fungi requires addressing the moisture problem contributing to its growth. Such corrective measures may include one of more of the following:

Substructure: Proper and adequate ventilation of the crawl space, installation of a six mil black polyethylene vapor barrier atop the entire subarea grade, installation of a system to remove excessive moisture (standing water) from the crawl space, repairing plumbing leaks.

Interior: Repairing plumbing leaks and roof leaks, ensuring adequate ventilation in the attic, kitchen, bathroom, and other moisture generating areas of the structure.

Exterior: Sealing uninfected wood thoroughly with a high-quality paint or waterproofing material, caulking/sealing to prevent moisture intrusion into or behind siding material, ensuring that roof drainage systems are working properly.

In all cases, wood that is damaged from wood destroying fungi must be removed to prevent the spread of damage. Reducing the ambient humidity or moisture content of rot damaged wood will not restore its structural integrity or original load-bearing strength. Scabbing new wood onto rot damaged wood will simply allow the existing fungi and damage to spread into the new wood. In cases where limited infection from fungi in its early stages has occurred (where damage has not yet taken place), wood can be professionally treated with a borate fungicide to kill the fungi before damage takes place.

The above preventative measures can also be applied to non-wood destroying molds and mildews that also frequent structures in the Northwest.

Carpenter ants are the most visible—and perhaps the most intimidating—of the structural pests encountered in the Pacific Northwest. Anyone who has witnessed a spring swarm of Camponotus modoc reproductives emerging from a window sill in their living room or flying throughout the interior of their home can likely attest to imagining visions of their house about to collapse from the shear number of these insects.

Carpenter ants can indeed do serious damage to structural members. Their primary interest in locating in a structure, however, is to use it as a nesting site. Carpenter ants do not eat wood, as termites or other wood destroying insects do. Instead they bore or mine wood out to create galleries to nest in and promulgate the colony. In fact, oftentimes a structural carpenter ant infestation may exist in or adjacent to the insulation of a structure rather than wood. They do not always seem to care what kind of material they nest in as long as it gives them the protection they need to survive and a relatively close proximity to a food and moisture source. The danger in their presence, no matter where in the structure they presently nest, is the risk of these ants moving into the adjacent wood where they can proceed to cause extensive damage as they expand their nest into wood members.

Nearly a dozen different species of carpenter ants reside in the Pacific Northwest. They range in size from the small Camponotus essigi, (sometimes confused with other kinds of ants because of their small size) to the large Camponotus modoc and Camponotus vicinus; the reproductives sometimes found in excess of an inch in length. They can infest a structure by a singular fertile reproductive establishing a colony, which can take three to six years for the colony to mature. They can also infest a structure by an entire colony—whether a parent colony or a ‘satellite’ colony—moving from one location to another (much as a swarm of bees might move from one place to another). They can be imported onto a property by delivery of landscape bark material from an infested site elsewhere or from firewood delivered from another area.

Click here for additional information on carpenter ants. 

Wood Boring Beetles

The Pacific Northwest is host to numerous species of wood boring beetles. The majority of these pests are more of a primary concern to agricultural or forestry interests rather than to the homeowner. However, some species greatly impact existing structures and should be addressed when infestation or damage is found. Wood borers go through a complete metamorphosis during their life cycle (egg, larva, pupa, adult). With most wood borers (except for ambrosia beetles, which do not infest seasoned wood), damage is caused by the larva.

For identification purposes, wood boring beetles are biologically grouped into families that share common characteristics, including habits of infestation.:

Lyctids: Infest only hardwoods (oak, walnut, mahogany, etc.) and not softwoods (pine, fir, Douglas-fir, hemlock, etc.). When emerging from wood, the adults leave behind round exit holes 1/32-1/16^th inch in size. Most commonly found in hardwood flooring and trimwork, lyctids will reinfest hardwood that is unfinished (not sealed with paint, varnish, etc.)

Corrective measures: Depending upon extent of infestation, it may require removal of the infested material, sealing uninfested wood, or having a professional perform local borate treatments or fumigation to arrest the problem.

Bostrichids: Generally infest only hardwoods, with a few exceptions. Prefer infesting standing timber, so infestation in structures is rare; most instances occur in newly constructed buildings where lumber was already infested. Once the adults emerge (one to five years, depending on species), they do not reinfest but move on to live wood. Examples include the large (1/2-7/8") black polycaon (Polycaon stouti), the lead cable borer (Scobicia declivis), and the bamboo borer (Dinoderus minutus) that can infest imported wood items.

Corrective measures: In a structure, once the adult has emerged no additional corrective measures are generally necessary since they tend not to reinfest seasoned wood. Regarding the bamboo borer, small items can be placed in plastic bags and put in a freezer (at least 0° F. or colder) for several days to kill the larva causing damage.

Cerambycids: Longhorned wood borers and round headed wood borers are included in this family. Species of this family that reside in the Northwest generally infest only standing timber or green lumber. The one general exception in the United States, the old house borer, is not found in the Pacific Northwest.

Corrective measures: Generally not required as these will not reinfest seasoned wood.

Buprestids: Examples of insects include short-headed wood borers, metallic wood borers, shot-hole borers, and the western cedar borer. These beetles infest softwoods, generally timber with bark on it that has been lightning struck, recently felled, or that is standing in fire swept areas. They generally do not reinfest seasoned wood.

One of the most commonly identified buprestids in the Pacific Northwest is the Golden Buprestid (Buprestis aurulenta). Though they infest only unseasoned wood as noted above, infested wood that has been milled and put into service has had these beetles emerge as late as 50 or more years after construction. When the timber is milled, the existing larva go into a state called diapause, which dramatically lengthens their life cycle. Generally it is not possible to detect infestation of these beetles until they emerge as adults (they leave an oval shaped exit hole up to 1/2 inch in size). Once they emerge, they seek out green timber so no corrective measures are required to protect a structure from reinfestation.

Anobiid beetles: Wood borers in this beetle family infest hardwood and softwood, green and seasoned wood. The anobiid of greatest structural economic importance in the Pacific Northwest is the Pacific powder-post beetle (Hemicoelus gibbicollis), also known as the California deathwatch beetle. Most common occurrences of infestation are in substructures with moisture problems. Anobiids need a moisture content in the wood of at 15% by weight to survive adequately. Unheated crawl spaces with damp exposed grades or seasonal standing water are at greatest risk of infestation. Once established, the adults will emerge from infested wood and lay eggs in the same or adjacent wood members, thus renewing the life cycle.

Anobiids leave exit holes that are round in shape, averaging 1/16-1/8" in size. The larva can spend one to three years burrowing in and consuming the wood before they pupate, leaving behind frass consisting of bun shaped pellets and loosely packed fine powder.

Click here for additional information on wood boring beetles.

Corrective measures: The moisture content of the environment where the infestation exists must be reduced to obtain control. Similar to reducing the risk of wood destroying fungi infection, vapor barriers, removal of standing water in a crawl space, and adequate ventilation are mandatory. Infested wood should be removed and replaced. Treatment by a licensed pest control operator of the undamaged wood and adjacent areas with a borate product can effectively ‘poison’ the wood and kill larva trying to consume it. In extreme cases, it may be necessary to consider space fumigation of the structure to eradicate a widespread infestation.

Subterranean Termites

Subterranean termites nest in the ground and infest wood directly in contact with the soil or by construction of mud tubes within which they travel to and from their nest. Though termites consume wood, they are unable to digest it but instead possess one-celled protozoa in their gut that breaks down the wood cellulose into a form that the termite can then consume.

Subterranean termites are social insects (much as honeybees, carpenter ants, and yellow jackets are social insects). Four ‘castes’ make up the framework of the colony: Primary and secondary reproductives, soldiers, and workers. In large colonies, the secondary reproductives produce the greatest share of offspring. Soldiers have large heads and mandibles; their sole purpose is to defend the nest from invaders. The workers, a cream-colored wingless creature, provide the food for the nest.

The species of primary economic importance in the Pacific Northwest is the Western subterranean termite (Reticulitermes hesperus) which is found from south-central British Columbia to northern Mexico. The workers and soldiers tend to be about 3/8 inch long; the winged reproductives are black and about 1/2 inch long excluding wings. Reproductives typically swarm either in the spring or early fall, depending on the individual colony.

Subterranean termites like moisture, but are discouraged by water saturated soil. They can travel up to 100 yards away from a nest to their food source. This often means that the point of infestation where termites are found in a structure does not necessarily indicate that the nest is in close proximity. Colony sizes can exceed 60,000 in number.

The most common sources where Western subterranean termites are found include earth-wood contact outside and under a structure, wood debris and form boards left under a structure, damp or poorly ventilated areas, cracks in continuous concrete foundations and slabs, and concrete slab locations where a heat source (furnace, hot water heater, or appliance) is in place.

Click here for additional information on termites.

Corrective measures: Eliminating moisture problems, eliminating earth-wood contact, and form board/wood debris removal are all vital. Because colony locations generally cannot be determined with certainty, synthetic pyrethroid products are generally applied to the soil either along the foundation, substructure pier pads, and/or under concrete slabs to create a barrier that termites cannot cross. Localized infestations may be controlled with other methods that are also effective.

Dampwood Termites

The Pacific dampwood termite (Zootermopsis angusticollis) is the largest of all native termites in North America. Workers and soldiers can be up to 3/4 inch in size, the reddish-brown reproductives can be up to 1 1/4 inches in length. The reproductives typically swarm in the late summer-early fall months.

Unlike subterranean termites, dampwood termites must have a wet environment to live. Generally they are found nesting above ground in damp or decaying wood. In structures they can infest wood in proximity to roof and plumbing leaks or wood in contact with damp earth. They can also invade sound, dry wood as long as damp wood is adjacent to the infested area (generally within 10-12 feet). Without a high moisture content in their nesting area these species of termites cannot survive. Dampwood termites leave behind a six-sided oval shaped fecal pellet in their galleries (subterranean termites do not).

Click here for additional information on termites.

Corrective measures: The most common measure of eradication is elimination of the moisture source promoting the development of dampwood termites. Repairing plumbing and roof leaks and replacing wet, damaged wood with new, dry wood will generally spell doom for a dampwood colony. Treatment of the affected and adjacent areas with a borate product will provide added insurance against reinfestation.