Termites are small, social insects that function as nature’s recyclers of dead trees but also destroy wooden structures. The primary factor influencing a termite’s diet is not the species of wood itself, but the specific chemical components within the wood fibers. Understanding why some woods are quickly consumed and others are left untouched requires examining the termite’s unique digestive biology and the inherent properties of various timber types.
What Termites Actually Consume
Termites specifically target cellulose, the primary organic polymer that gives wood its structure. Cellulose is a complex carbohydrate that termites cannot break down using only their own digestive enzymes. Wood also includes lignin, a rigid polymer that is difficult to digest, which is why woods with higher lignin content are less appealing.
To access the energy in cellulose, termites rely on a symbiotic relationship with microorganisms living in their hindgut. In lower termites, specialized protozoa perform this digestion, often harboring bacteria that produce the cellulase enzymes necessary to hydrolyze cellulose into simpler sugars. The microorganisms break the complex cellulose chains into usable short-chain fatty acids, primarily acetic acid, which the termite absorbs as nourishment.
Higher termites rely more on bacteria and their own secreted enzymes to process cellulose. This biological dependence explains why termites are drawn to the soft, digestible parts of wood and other cellulose-based materials like drywall paper and cardboard.
Wood Types Termites Prefer
Termites prefer woods with lower density and a higher ratio of accessible cellulose to lignin. Common softwoods like Pine, Fir, and Spruce are vulnerable, making them frequent targets for most termite species. These woods are structurally softer, requiring less effort for termites to chew through and establish feeding galleries.
Moisture content is a significant determinant of wood preference, particularly for subterranean and dampwood termites. Termites seek wood that is damp, decaying, or infested with fungus. Fungal decay softens the wood and predigests some of the cellulose, making the material easier to penetrate and consume.
Subterranean termites live in soil and must maintain a high-moisture environment, using mud tubes to reach wood softened by water damage. Drywood termites infest wood that is dry and above ground, such as furniture or structural beams, but they still prefer less dense woods. Untreated wood in direct contact with soil or exposed to constant moisture becomes an immediate food source.
Wood Types That Resist Termites
Certain types of wood are naturally resistant to termites because they contain specialized chemical compounds called extractives. These compounds are concentrated in the heartwood, the dense, non-living core of the tree, and are often toxic or repellent to wood-destroying insects. Species such as Redwood, Cypress, and Cedar achieve their natural resistance from these extractives.
The outer sapwood of these trees offers little resistance and is susceptible to attack. The effectiveness of naturally resistant wood can also diminish over time as the extractives leach out due to weathering and water exposure. For long-term protection, pressure-treated lumber offers a more reliable defense mechanism.
Pressure-treated wood is infused with chemical preservatives, such as Alkaline Copper Quaternary (ACQ) or Micronized Copper Azole (MCA), forced deep into the wood fibers. These chemicals render the cellulose indigestible or toxic to the termites, creating a chemical barrier within the wood. This process ensures the wood’s resistance is uniform and long-lasting, even when used in environments with high moisture or soil contact.
Protecting Existing Wood Structures
Protecting an existing home involves proactive maintenance focused on eliminating the environmental conditions that attract termites. Since moisture is a primary factor, fixing plumbing leaks, leaky roofs, or air conditioning condensation issues is essential. Ensuring that gutters and downspouts direct water away from the foundation is also important to keep the soil dry.
Homeowners should ensure there is no wood-to-soil contact around the perimeter of the structure. A minimum clearance of six inches between the soil grade and any wooden siding helps prevent subterranean termites from easily accessing the home. Firewood, lumber, and other cellulose debris should be stored off the ground and a distance away from the foundation.
Proper ventilation in crawl spaces and basements is necessary to reduce humidity levels, which deters moisture-seeking termites. Sealing cracks and gaps in the foundation or utility entry points with a durable sealant deprives termites of easy access routes. Regular, professional inspections are the most effective way to detect early signs of infestation, such as mud tubes, before extensive damage occurs.