Drywood vs Subterranean Termites in Florida Homes
Subterranean termites nest in soil, need soil moisture, and build pencil width mud tubes up foundations and piers to reach wood. Drywood termites live entirely inside the wood with no soil contact and push out hard six sided frass pellets that pile up like coarse pepper. Subterranean work means a soil barrier or bait system. Drywood work means wood treatment or fumigation.
Two termites can chew the same piece of Florida pine and leave completely different evidence behind. That is lucky for homeowners, because the evidence is usually visible from a stepladder and a flashlight, and it decides which treatment is worth paying for.
The split comes down to water. Subterranean termites cannot hold moisture in their bodies, so they live in the soil and carry the soil with them when they travel. Drywood termites extract enough moisture from the wood itself, so they never touch the ground at all. Everything else about the two follows from that one difference.
How do I tell them apart without an entomologist?
Go by what they leave, in this order.
| Clue | Subterranean | Drywood |
|---|---|---|
| Mud tubes | Yes, pencil width, on foundations, piers, slab edges | Never |
| Frass pellets | No visible pellets, waste goes into the tubes | Yes, hard six sided pellets, like coarse pepper |
| Soil contact | Required | None |
| Where damage starts | Low, near ground level, moving up | Anywhere, often high: attic wood, fascia, trim, furniture |
| Colony size | Very large, often in the millions for Formosan | Small, usually hundreds to a few thousand |
| Galleries | Packed with soil and mud | Clean, smooth, sanded looking |
| Typical swarm | Spring, daytime for natives, dusk for Formosan | Later spring into summer |
| Treatment | Soil barrier or in-ground bait system | Local wood treatment or whole structure fumigation |
Mud tubes and frass are the two clues that settle almost every case. If you find hard little pellets on a windowsill under a wooden frame, you are looking at drywood. If you find a mud tube on a block pier, you are looking at subterranean.
What do frass pellets actually look like?
They are smaller than people expect. Each one is roughly a millimeter long, hard, and hexagonal in cross section with six flat sides and rounded ends. Color follows the wood, so they range from cream to dark brown. A drywood colony pushes them out of a kick hole in the surface of the wood, and they land on whatever is underneath.
The pile is the tell. Sweep it up. If it comes back in a few days, the colony above it is active. If it never returns, you may be looking at an old infestation that was already treated or died out, which matters a great deal when you are pricing work.
Frass is sometimes confused with sawdust from carpenter bees or wood boring beetles. Sawdust is loose and irregular. Drywood pellets are uniform and roll under your finger like tiny grains.
Why do mud tubes matter so much?
A mud tube is a covered road. Subterranean termites build them out of soil and saliva to cross an exposed surface without drying out, and they run from the ground up to whatever wood the colony is feeding on. They are the width of a pencil, sometimes wider, and they show up on foundation walls, block piers, the inside of crawl spaces, slab edges, plumbing penetrations and even on the outside of a house where mulch is piled high against the wall.
Break a small piece out of a tube and look. Live workers inside mean an active colony. An empty tube that gets repaired within a few days also means an active colony. A dry, crumbling tube that stays broken may be old.
The Formosan subterranean termite is the one that scares professionals. Its colonies run into the millions and its workers can forage a long way through soil, which means the nest may sit well off your property while the damage happens under your floor. UF/IFAS reports it is now present across almost every major urban area in Florida.
Which one is my house more likely to get?
Both, depending on the house and the block.
The 1920s bungalows in Seminole Heights are a drywood termite favorite. Original heart pine trim, wood windows, exposed rafter tails and decades of small repairs give a drywood colony plenty of untreated wood to work in, and much of it sits high up where nothing ever gets inspected. Attic framing and fascia boards are common finds.
Subterranean pressure is more about the ground. Slab homes with cracks, expansion joints or utility penetrations give colonies a way in. Mulch piled against siding, a downspout that dumps at the foundation, an irrigation head soaking one corner of the house and wood stored against an exterior wall all help. Crawl spaces with poor drainage are the worst case.
Can one house have both?
Yes, and it happens here more than people expect. A subterranean colony working the sill plate at ground level has nothing to do with a drywood colony in the attic rafters twelve feet above it. Neither one competes with the other, and an inspection that finds one should keep looking for the other.
This is also why a single treatment rarely covers a house completely. A liquid soil barrier does nothing for drywood termites in an attic. A drywood fumigation kills what is inside the structure on that day and leaves no residual protection in the soil against the next subterranean colony that shows up.
What does the treatment difference look like in practice?
For subterranean termites there are two routes. A liquid barrier is trenched into the soil around the foundation, with drilling through slabs, patios and garage floors where needed, so that any termite passing through the treated soil picks up the product. An in-ground bait system puts stations in the soil around the house, and workers carry the active ingredient back to the colony. Both are ongoing relationships: the barrier eventually needs renewal, and the stations need checking through the year.
For drywood termites, the choice depends on spread. A localized infestation in one window frame or a run of fascia can be treated in place, by drilling and injecting the galleries. An infestation in multiple areas, or in framing you cannot reach, usually points to whole structure fumigation, where the building is tented and the gas reaches wood no drill can. Fumigation is handled by a licensed fumigation company and priced by cubic foot.
Whatever gets applied, it goes down according to the product label, and you can ask for the product name and label information at any point.
Getting a straight identification
The identification decides the price, so it should come before the quote. Our termite control page sets out what the inspection covers and what each treatment path costs in the Tampa market. If you have wings or pellets in a bag, hold onto them and show us at the visit.