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Drywood Termite (Kalotermitidae)
- Nest above ground, away from soil -
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Summary: Drywood termites are important structural pests in tropical and warm/dry climates. Unlike their subterranean termite cousins, drywood termites do not need contact with soil moisture. Control of drywood termites can be difficult because they may not leave their colony.
Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)
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How to identify drywood termites
 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 Related Articles below).
Where do drywood termites occur?
In the US drywood termites are found in regions that do not experience freezing temperatures 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.
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Distribution map for termites in the US. Red = both drywood and subterranean termites, green = 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.
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How do I detect a drywood termite infestation?
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.
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What does drywood termite damage look like?
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).
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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.
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Treatment & 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 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, for example, reconstruction or remodelling. These found colonies can be treated by drilling into the wood and injecting insecticide such as Bora Care, Termidor or Premise directly into the tunnels.
Drywood termite infestations can be prevented by the use of treated or sealed wood. Wood that has been surface-treated with borate, copper-arsenate preservative ("pressure treated") or painted will stop an initial attack, but cracks or cuts must be retreated.
If the infestation is widespread it may be necessary to "tent and fumigate". 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 Related Articles below for much more detailed information about these control methods.
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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.
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Jack DeAngelis, Ph.D.
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