Wood Destroying Insects (WDIs): Inspection, Prevention, and Treatment

Wood Destroying Insects (WDIs), if not managed, can cause significant damage to homes over time. Nearly all homes are at risk from these pests. The main culprits are termites, carpenter ants, carpenter bees, and wood boring beetles.

Some states or lenders, like in Pennsylvania, require inspectors to be licensed in chemical application in order to perform a Wood Destroying Insect (WDI) Inspection. While some home inspectors hold licenses for pesticide application, they may not use pesticides professionally but must be insured for it. In many cases, the state’s Department of Agriculture is the licensing authority for pesticide applicators. Inspections should be documented, as commonly requested by lenders, and inspectors should provide their license number. Performing both inspection and treatment for WDIs on the same property might be seen as a conflict of interest.

WDI inspections, which can also include checks for fungus and mold, are not typically included in a standard home inspection, though you should check with your local home inspector as some inspectors include them or offer them as additional services.

A WDO/WDI or Termite Inspection may also be referred to as a ‘wood infestation’ or ‘pest’ inspection. The goal is to identify any visible signs of current or past infestation by looking for typical indicators left by these insects. Similar to home inspections, WDI inspections are non-invasive and don't involve moving household items or structural components.

Annually, over $3 billion is spent on treating WDIs and termites; however, with regular maintenance by homeowners, the prevalence and severity of WDI infestations could significantly reduce. These insects typically seek wood either for consumption or nesting, and limiting their access to wood is an effective strategy in preventing these pesky pests from making your home their home.

A common prevention method is to keep vegetation trimmed away from the home and roof. Vegetation like ivy, bushes, or tree branches touching the house can provide easy access for insects. Similarly, maintaining a gap of at least 4” between wooden structures (like siding and trim) and the ground is crucial. This not only deters insects, but also prevents water damage and wood rot. Other prevention strategies include applying mulch near the house carefully (as this can create ideal conditions for insect entry), promptly repairing of any exterior wood rot (it attracts WDIs and provides moisture), and storing firewood off the ground and away from the house.

Poor drainage is another factor attracting WDIs - issues like clogged gutters, downspouts releasing water near the foundation, and improper grading can all contribute. It’s recommended to ensure your gutters and downspouts are clean and send water at least four feet away from the house.

Inspecting for WDIs during colder months (usually October to April) often reveals past infestations or damage rather than active ones, as many WDIs go dormant in cold weather and are less detectable. Now that we’ve laid the groundwork for what WDIs are, what causes them to breach your home, and how to prevent them, let’s take a closer look at each type of pest so you can familiarize yourself in the event you find one of these creepy crawlers in your home.

Termites

Termites, notorious for their ability to significantly damage structures by consuming wood, are the most prevalent wood destroying insects. In contrast to other WDIs, termites tend to eat the wood rather than nest in the wood. Subterranean termites, which are commonly found in south-central Pennsylvania, usually establish their colonies near food and water sources. It often takes years for termites to cause considerable damage to a home, accentuating the importance of regular inspections to prevent this costly damage. Every year, termites are responsible for damaging around 600,000 homes in the U.S., contributing to an estimated $30 billion in damage to buildings and agricultural crops.

It's important to differentiate between termites and carpenter ants. Commonly confused for one another, termites have a uniform, light cream-colored body with straight antennae, whereas carpenter ants are darker (brown or black), have a segmented body, and bent antennae. Both insects swarm during new nesting periods, typically in spring. Finding discarded wings can indicate an infestation, with termites having four wings of equal size and carpenter ants possessing two sets of differently sized wings.

Termites build shelter tubes or mud tubes to move around and protect themselves from air exposure. These light-brown tunnels, about 1/8-1/4” in width, can be short or extend several feet, resembling stalagmites or stalactites.

Severe termite damage can leave wooden structures like joists almost hollow, producing a crinkled paper sound when probed and causing it to lose its structural integrity. However, a wood destroying insect inspection is not a structural assessment. If structural damage is detected, the inspector typically recommends a qualified contractor for evaluation and repair. It’s important to note that WDI inspections are visual and non-invasive, meaning unseen damage may exist. Some lenders may require a structural certification from an engineer for certain loans. Home inspectors, who are not structural engineers, generally do not provide such certifications, and those offered by some may lack credibility.

The inspection process involves examining the home's exterior perimeter and interior visible wood structures. If termite damage is discovered without evidence of prior licensed extermination, the inspector will usually recommend a termite treatment. This often involves liquid treatment around the home's perimeter underground; however, bait stations are another method. Signs of previous treatments, like small concrete patches in a patio, don’t guarantee effectiveness, and the inspector typically can't confirm the treatment date.

Carpenter Ants

Carpenter ants, another prevalent type of wood-destroying insect, are typically about ½” in length and usually black in color. They resemble larger versions of the common 'black ants' often seen on sidewalks. However, unlike termites that consume wood, carpenter ants nest within it. Generally, the damage caused by carpenter ants is less extensive compared to that of a termite colony, but effectively treating a carpenter ant infestation requires skill and sometimes luck.

One of the telltale signs of a carpenter ant infestation is the presence of frass, which resembles small, light brown or grey sawdust particles. As carpenter ants create their nests inside wood, they excavate these particles to make room, often depositing the frass outside the nest. Similar to termites, carpenter ants are drawn to rotted wood, both inside and outside of homes. They are also attracted by moisture sources such as roof and plumbing leaks. Carpenter ants have a diverse diet, consuming almost anything humans do.

When inspecting for carpenter ants, probing exterior wood to locate soft, damaged areas is a common practice. If soft wood and carpenter ants are found together, it likely indicates the presence of a colony. Unlike termite treatments, which are typically applied more broadly, treatments for carpenter ants are usually localized to the area where the colony or nest is discovered.

Carpenter Bees

Similar to carpenter ants, carpenter bees do not eat wood but rather use it for nesting purposes. They commonly target wood siding and trim, boring holes about ½ to ¾ inches in diameter. After entering the wood, they typically turn right or left to follow the wood grain to their nesting site. Carpenter bees are similar in appearance to bumble bees, but they can be distinguished by their black, shiny tail section. They are often observed hovering near wooden structures such as trim, railings, fascia, or soffit boards. Signs of carpenter bee activity include coarse sawdust or droppings found beneath entry holes.

Male carpenter bees are not equipped with stingers, yet they may aggressively approach other insects or people near their nests. Female carpenter bees, while possessing stingers, rarely use them. The damage caused by carpenter bees usually isn't as extensive as that from other wood-destroying insects. Treatment typically involves applying pesticide directly at the nesting or bore holes. Preventing carpenter bee infestations can be challenging, but reducing exposed wood on the exterior of a home and maintaining well-stained or painted surfaces can be effective deterrents. After addressing a carpenter bee infestation, we recommend sealing or screening over the holes, or replacing the affected wood entirely.

Wood Boring Beetles

Wood boring beetles are another category of pests that can infest wood floors, wood furniture, or even trim. These beetles typically range in size from 1/4” to ¾” long. The exit holes they create in wood are usually very small, about the size of a pinhead, and their activity may result in complex galleries within lumber. A common way for these beetles to enter your home is through old furniture, where they nest and lay eggs inside the wood. Most types of wood boring beetles tend not to infest wood that has been painted or varnished. The exit holes may show small amounts of frass (sawdust-like debris), which can vary inside or outside the holes based on the beetle species.

An infestation in homes often originates from larvae already present in lumber before construction. To gauge the recency of a beetle infestation, a professional can take a look at the color of the frass: newer infestations typically have lighter, fresher-looking frass (similar to newly cut sawdust), while older infestations are indicated by darker, aged-looking frass, or in some cases, the absence of frass if it has been cleaned away. Treatment for beetle infestations might involve a localized treatment of the affected lumber, or in more severe cases, full fumigation.

In our experience, homeowners should be vigilant against these wood destroying insects (WDIs).

Termites, carpenter ants, carpenter bees, and wood boring beetles are all attracted to the wood in your home and each cause a distinct form of damage to your home’s structural integrity. Regular inspections and prompt repair of damaged wood are key strategies in preventing and managing these common household pests.