Termites are prevalent across California, where these wood-destroying insects thrive in nearly all regions. The state’s diverse geography, including humid coastlines, arid valleys, and mountainous regions, creates a unique hotspot for multiple termite species. Vigilance against infestation is a year-round necessity for property owners. Termites are responsible for causing millions of dollars in structural damage annually throughout the state.
The Major Termite Types in California
Subterranean termites, primarily the Western subterranean termite (Reticulitermes hesperus), are the most destructive species in California due to their large colony sizes and rapid consumption rate. These termites require constant contact with the soil to maintain the high moisture levels necessary for their survival. They construct pencil-diameter mud tubes to travel between their underground nest and the cellulose material they consume in a structure. A single mature colony can contain hundreds of thousands of individuals, allowing them to consume wood rapidly and cause extensive damage to a structure’s foundation and framing.
Drywood termites, most commonly the Western drywood termite (Incisitermes minor), are a significant threat. Unlike their subterranean counterparts, these insects do not require contact with the soil and can live entirely within the dry wood they infest, threatening upper-level framing, furniture, and attic spaces. Drywood colonies are much smaller, typically fewer than 1,000 individuals, but they are difficult to detect because they do not leave mud tubes. The most telltale sign of their presence is the characteristic fecal pellets, or frass, which they push out of small “kick-out” holes in the wood.
Dampwood termites are the largest of the three groups, with some soldiers reaching up to three-quarters of an inch in length. This species, which includes the Pacific dampwood termite, requires wood with a very high moisture content, often due to plumbing leaks, poor ventilation, or wood that is in contact with the ground. They do not build mud tubes, and their presence often indicates a significant underlying moisture problem within a structure. Dampwood termites are generally found in cool, humid areas along the coast. While they can cause significant damage to localized areas of wet wood, they are less common structural pests than the other two species.
Geographic Distribution and Risk Factors
The distribution of termites across California is heavily influenced by the state’s varied climate zones, with different species dominating in specific geographic areas. Southern California, including the coastal regions and inland valleys, is a high-risk area, frequently hosting both subterranean and drywood termites. The warmer temperatures and mild winters in these southern and central regions create ideal conditions for year-round activity and swarming. Most of Southern and Central California is classified as having a heavy to moderate risk of infestation.
Coastal areas, stretching from San Diego to the Bay Area and northward, are especially prone to dampwood termites due to the consistent high humidity and cool temperatures. These areas frequently feature the decaying, moist wood that dampwood termites require. In contrast, the more arid inland areas and deserts are generally lower risk. However, they still contain specialized species like desert subterranean termites, which can be found even at elevations above 8,000 feet.
Environmental factors are linked to the risk of infestation, particularly the availability of moisture. Subterranean termites are often found where soil meets a structure, and they thrive in areas with poor drainage or leaky pipes that provide a consistent water source. Drywood termites are drawn to warm, dry environments like attics and upper wood framing, where they establish colonies without any soil or external moisture contact. Any condition that introduces or traps moisture in wood, such as leaky roofs or clogged gutters, increases the likelihood of a localized dampwood or subterranean infestation.
Identifying the Signs of Infestation
Homeowners can look for several visual cues that indicate a termite infestation is active. One of the most noticeable signs is the presence of swarmers, which are winged reproductive termites that emerge from a mature colony to establish a new one. Finding piles of discarded wings near windowsills, doors, or light fixtures is a common indication that a swarm has occurred. Swarming can happen at different times of the year depending on the species, with subterranean termites often swarming after a rain event and drywood termites typically swarming in the late summer or fall.
The fecal pellets, known as frass, are a direct sign of drywood termite activity. These small, hard, six-sided droppings are often wood-colored and accumulate in tiny mounds near the infested wood, sometimes right below a small “kick-out” hole. Finding these pellets in a quiet corner of an attic, garage, or on a window ledge suggests a drywood colony is present. Dampwood termites do not always push frass out, but may use it to plug up tunnels to maintain humidity.
Subterranean termites leave behind a diagnostic sign known as mud tubes. These are pencil-sized tunnels made of soil, wood particles, and termite saliva that run along foundation walls, concrete slabs, or into crawl spaces. The tubes serve as protected runways that allow the subterranean termites to travel from their moist underground nest to the wood source. Wood damage itself may also be evident, often sounding hollow when tapped, as termites consume the interior material while leaving an outer veneer intact.