Effects of Nootkatone and a Borate Compound on Formosan Subterranean Termite (Isoptera: Rhinotermitidae) and Its Symbiont Protozoa

Wood treated with disodium octaborate tetrahydrate, with nootkatone, a natural extract isolated from vetiver oil, or with both nootkatone and disodium octaborate tetrahydrate was tested for effects on Coptotermes formosanus Shiraki and its hindgut flagellates. Results demonstrated that after 7 d disodium octaborate tetrahydrate-treated wood induced high termite mortality and almost complete loss of flagellates, confirming the toxicity of borates to these termites. Wood treated with nootkatone alone or with the nootkatone-borate mix was consumed in significantly lower amounts than the control, and termite survival was comparable to results obtained for starved termites. A significant progressive reduction in the total number of protozoa was observed for all groups, including the controls. We conclude that nootkatone acts as a feeding deterrent, inducing starvation that results in almost a complete loss of Pseudotrichonympha grassii Koidzumi, the most important flagellate species for cellulose digestion in this termite.