Orange oil can kill termites, including drywood termites, subterranean termites and Formosan termites. Unfortunately, orange oil is not as reliable a method for killing termites as more conventional insecticides.
The ingredient in orange oil extract that kills termites is called d-limonene. It kills termites through direct contact from the termite eating wood coated with orange oil and from the termite breathing in the fumes.
Orange oil is far less toxic to people, pets and wildlife than conventional insecticides. It also has a pleasant odor and is considered to be safer for the environment.
In a study done by the University of California, one brand of orange oil killed less drywood termites in 24 hours than more conventional insecticides. Orange oil is not as effective for heavy infestations, which may require fumigating a home with an insecticide such as sulfuryl fluoride.