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Drywood Termite (Kalotermitidae)

- Nest above ground, away from soil -

Summary: Drywood termites are important structural pests in tropical and warm/dry climates. Unlike most other termites, drywood termites do not need contact with soil moisture. Control of "drywoods" can be more difficult because their colonies are not confined to the soil.

Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)

Drywood termite identification

Unlike subterranean termites which built colonies in the soil, drywood termite colonies do not need contact with soil moisture nor any other water source. As their name suggests, drywood termites occur in dry wood that may be above ground level. Drywood termites build colonies in structural wood (see pictures below), fence and utility posts, furniture, moldings, door and window frames, and so forth. Because termite workers can be difficult to identify, species are often determined based on geographical location, location of colony and/or type of wood damage (see How Are Subterranean Termites Different?).

Drywood termite map

In the US drywood termites are found in regions that do not experience freezing temperatures during most winters (red areas of map, right). Isolated infestations may occasionally be found north of these areas however. Drywood termites also may be transported in wooden articles and start local, indoor infestations anywhere.

drywood termite distribution map

Distribution map for termites in the US. Red = regions where both drywood and subterranean termites occur, green = regions where only subterranean termites, white = little or no significant termite activity. Modified from original drawing in Wood-Inhabiting Insects in Houses by Harry B. Moore, 1979. USDA, Forest Service and HUD.

Detecting drywood termites

Since colonies are usually constructed inside wood, finding these termites can be difficult during routine pest and dry-rot inspections. Therefore, one of the best ways to identify an active infestation is the presence of fecal pellets.

Drywood termite fecal pellets are kicked out of the colony by workers and may accumulate below infestations. Fecal pellets have a distinct ridged shape and are about 1/25" long (about the size of table salt). Subterranean termites do not kick out dry fecal pellets from their colonies and drywood termite fecal pellets are much larger than the boring dust particles of powderpost beetles.

Drywood termite damage

Wood is damaged as the drywood worker termites tunnel to enlarge their colony. Drywood termite galleries cut across the wood's grain (right) thus weakening the wood's internal structure and eventually the wood fails. Fecal pellets may be packed into some of the galleries

Drywood termite damage tends to progress more slowly than damage from subterranean termites but because it is so difficult to detect, considerable damage, extending over a wide area, may be present by the time it is first found (below right).

drywood termite damage cross-section

Cross-section of a 2x4" with drywood termite galleries. Original drawing from Wood-Inhabiting Insects in Houses by Harry B. Moore, 1979. USDA, Forest Service and HUD.

Treatment and control of drywood termites

Drywood termite control is generally not a DIY project for most homeowners. Baiting, which is effective for some other termites, is not an option because drywood termites never leave the protection of their galleries. Perimeter sprays, that are effective for carpenter ants, won't work here either. And, treating the soil under and around the structure with a termiticide, which is used for subterranean termites, does not work because drywood termites may never contact the soil.

Limited control can be achieved by treating individual colonies as they are found during reconstruction or remodeling. These found colonies can be treated by drilling into the wood and injecting insecticides such as Bora Care, Termidor or Premise and/or several foam-type insecticides directly into the tunnels (see this page at DoMyOwnPestControl for more info) and see Bora Care Insecticide and Termidor Insecticide.

Drywood termite infestations can be prevented by the use of pressure treated wood. Wood that has only been surface-treated with borate, copper-arsenate preservative, or paint will stop an initial attack, but new cracks or cuts must be retreated.

drywood termite damage

Drywood termite damage seen in a cut-away wall. Note colonies in floor and ceiling rafters. Original drawing from Wood-Inhabiting Insects in Houses by Harry B. Moore, 1979. USDA, Forest Service and HUD.

If the infestation is widespread it may be necessary to "tent and fumigate" the whole building. This is an expensive and difficult procedure and is definitely not a DIY project. In the final analysis you may need to hire pest control services to deal with an established infestation of drywood termites (see Fumigation for Structural Pests).

Related Article:

Regular Inspections Can Prevent Termite Damage

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