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.
2Department of Biological Sciences, Louisiana State University, 320 Choppin Hall, Baton Rouge, LA 70803, USA.