By some estimates, termites cause about $40 billion per year in damage globally, and they destroy parts of more than 600,000 homes in the United States alone.

The amount of wood a single colony destroys depends on the type of termite and the type and condition of the wood. For example, the heartwood of some trees contains allelochemicals, which can act as repellents and toxicants to termites.

But which types of wood actually contain enough of these chemicals to have a real impact against termites? In order to find out, entomologists from the USDA’s Agricultural Research Service tested Formosan subterranean termites (Coptotermes formosanus) on a diet of commercial lumber from 10 different species of wood, including redwood, birch, spruce, southern yellow pine, red oak, Brazilian jatoba, Peruvian walnut, Honduran mahogany, teak, and Alaskan yellow cedar.

When termites were given no choice but to consume just one variety of wood for six weeks, six of the woods (redwood, Brazilian jatoba, Peruvian walnut, Honduran mahogany, Alaska yellow cedar, and teak) showed some level of natural resistance and on average caused 75 percent or more of the termites to die.

The termites found southern yellow pine and spruce the most palatable, and teak was the least palatable. The termites had significantly lower survival rates on a diet of teak compared to termites that were not fed any wood at all. This indicates that there is something in teak that actively kills the termites.

“Our ranking could be a guideline when it comes to a choice of lumber in major termite-ridden areas,” said Mary L. Cornelius. “If the specific compounds in the resistant woods are identified, these chemicals could eventually offer the possibility of a natural treatment for wood to protect against termites.”

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– Natural resistance of exotic wood species to the Formosan subterranean termite (Isoptera: Rhinotermitidae)