Wood that has been damaged by subterranean termites will have a honeycombed or layered appearance when broken open. Termites prefer to eat the softer spring wood, leaving the summer wood. Galleries in the wood usually run parallel to the grain. They are messy, containing a mixture of solid and digested wood, and soil. Gallery walls have a yellowish or grayish-brown, speckled appearance from soft fecal material that termites plaster on the surface.
Subterranean termite galleries do not contain any wood frass, fecal pellets, or sawdust-like material and there is no similar material kicked out of the galleries. If you see sawdust, you are not dealing with termites. There is no sawdust because termites eat the wood that they excavate and they don’t chew exit holes that produce sawdust. If a gallery is active, you may see workers and soldiers in the wood when you break it open. There may be mud tubes in crevices of the infested wood.
Termites may continue to feed until only a thin outer shell of wood remains. Unpainted wood often appears undamaged on the surface, or it may have dark, blistered areas on the surface. These areas can be easily crushed with a knife or screwdriver. Painted wood may also look “blistered” and termites may have consumed the paper from between the gypsum and the paint on plasterboard. Vinyl floor coverings may have irregular sunken areas. Termite-damaged wood will have a hollow sound when tapped. Heavily infested wood splinters and breaks apart easily during probing with a screwdriver or other tool.
Termites will even infest live trees and shrubs, but they don’t just damage wood. They can also damage other materials, especially if the materials are in contact with soil or are damp: composition board, paper, cardboard, fiberboard, insulation, and certain fabrics made from plants like cotton. On carpeted floors, there may be holes where the termites have chewed on the carpet backing, leaving loose, unattached fibers.