Fumigant Toxicity of Essential Oils to Reticulitermes flavipes

Subterranean termite infestations occur in every state in the contiguous United States and are responsible for damage to wooden structures in excess of two billion dollars (U.S.) annually. Essential oils have historically been used to repel insects. They have relatively low toxicity and some of them are exempt from regulation by the Federal Insecticide Fungicide and Rodenticide Act (FIFRA). Development of environmentally friendly wood protection systems may benefit from supplemental essential oils. Eight essential oils were evaluated for their ability to protect wood from attack by Reticulitermes flavipes (Kollar), either in the fumigant toxicity test or by surface treatment in laboratory tests. In a fumigant toxicity test, 5 ml of dill weed or rosemary oil and 10 μl lemongrass oil per 553 cm3 air caused 100% mortality after 24 h in a closed container. The estimated LD50 for dill weed was 2.93 μl/m3. In the surface treatment test, essential oils tested in concentrated form caused 100% mortality after 24 h. Geranium (Egyptian), lemongrass, and tea tree oils caused 95% to 100% mortality after 24 h when diluted 1:50. In light of fumigant toxicity findings, mortality in surface treatment tests can be attributed to the volatility of essential oils. These results suggest that dill weed, lemongrass, tea tree, rosemary, or geranium (Egyptian) essential oils could be used alone or as a co-termiticide fumigant for wood product applications to protect structures from termite attack.