Drywood vs. Subterranean Termites

Drywood termites: the colony inside the board

A drywood colony needs no soil and no water source. It never touches the ground. The whole colony lives inside the piece of wood it’s eating. That means the king, the queen, and a few thousand workers, all sealed in one board. They pull the water they need from the wood itself. That’s why drywood termites turn up in attic rafters, fascia boards, window frames, and garage framing. They even live in furniture. One infested antique can start a problem in a house that never had one.

Since the colony is sealed inside, the evidence is whatever escapes. Drywood termites keep their tunnels clean by pushing droppings out through pinholes called kick-out holes. Those droppings are frass. The pellets are hard, dry, and six-sided, like coarse ground pepper. Find a fresh pile and there’s an active colony within a few feet of it. The upside is pace. A drywood colony holds thousands of members, not hundreds of thousands. Damage builds slowly, board by board. Read the evidence early and you have time to act. No-tent local treatment can handle small, contained cases. Infestations spread across the house push toward whole-structure methods. That choice gets its own guide.

Subterranean termites: the colony under the yard

The western subterranean termite is Fresno’s main termite by a wide margin. It works the opposite way from drywood. The colony lives in the soil, where the moisture is. It can hold hundreds of thousands of workers. Those workers tunnel through the ground to reach wood. When they have to cross open air, they build mud tubes. These are covered dirt tunnels that give them away. Look for them running up stem walls, piers, and around pipes. Break one open. Live workers inside mean an active colony is commuting through it.

Moisture is their one big need, and Fresno hands it to them. Summer here should bake the ground dry. Instead, lawns and drip lines keep the soil damp right against foundations. That’s why subterranean pressure stays steady all year instead of coming and going. They’re also the bigger structural threat. A large soil colony feeding on sill plates and floor framing eats far more wood per year than a drywood colony sealed in one board.

Swarm timing splits the species too. Subterranean swarmers fly on warm days after the first soaking fall rains. Some fly again in spring. Drywood swarmers pick hot, still afternoons in late summer. Either way, treatment goes where the colony lives. For this species, that means at the soil, not in the wood alone.