UC Riverside

Colonies of drywood termites (Blattodea: Kalotermitidae) are difficult to detect and treat due to their cryptic nature. Besides several chemical options, the use of heated air to create lethal temperatures for the termites within the infested wood is considered as a non-chemical treatment option. Even if heat is effective in killing the termites, the presence of hard-to-heat areas and potential risk of heat damage for plastics and other heat-sensitive items are recognized as important drawbacks. To address these challenges, the incorporation of a volatile essential oil constituent was tested as a means to increase the overall efficiency of heat treatments for drywood termites. Using field-collected individuals of the western drywood termite, Incisitermes minor (Hagen), two studies were conducted to evaluate this treatment combination. First, scaled-down wooden arenas were placed in a gas chromatograph oven to simulate several types of heat treatment. A simulated structural heat sink was also included in some experiments. When there was no heat sink, the 2-h treatment at 47.7 °C achieved 100% mortality by day 7. However, when there was a heat sink, 49.5 °C was necessary to achieve 100% mortality. The injection of a small amount of volatile essential oil in the arena increased the overall effectiveness even with the presence of a heat sink, resulting in 100% mortality at only 45.6 °C. Next, a full-size test structure was used to simulate a real heat treatment with and without the essential oil. Larger wooden arenas were used to more accurately simulate infested wood and were placed in the test structure during treatment. In areas of the structure shielded by heat sinks, mortality was significantly higher with the essential oil added (~90%) than without (~40%). The ability to achieve complete control of the termites even at sub-target temperatures could improve the overall efficacy of the heat treatment while reducing the potential risks of heat damage.