Although boric acid and other boron compounds have been used since the 1800s as insecticides, their mode of action is not well understood. Borate salts, in particular sodium and zinc formulations, are effective wood preservatives and are used extensively in Hawai’i to protect building materials from both drywood (Kalotermitidae) and subterranean (Rhinotermitidae) termites. The Formosan subterranean termite, Coptotermes formosanus Shiraki, is the most important insect pest in the state, causing over $100 million in prevention and repair costs. In order to determine whether different borate salts elicit different responses in C. formosanus, termite workers (undifferentiated individuals) were collected from field colonies maintained in Honolulu, Hawai’i, and exposed to composite board samples of different borate salt formulations in the laboratory. The treatments included zinc borate (ZB) (0.88% and 0.18%), disodium octaborate tetrahydrate (DOT) (ZB and DOT in a 60/40 and 80/20 ratio), anhydrous boric acid (B2O3) (60/40 and 80/20 ZB/B2O3), and an untreated composite board control. Activity and mortality data were recorded over a 4-week period; results suggest the concentration of boron in the wood sample, rather than the associated salt, has a greater impact on termite feeding, and that anhydrous boric acid reduces termite feeding more rapidly than the other formulations tested. Inductively Coupled Plasma - Atomic Emission Spectrometry (ICP-AES) was used to determine boron ingestion after five days of exposure to high-concentration (ZB 0.88%, 60/40 ZB/DOT or 60/40 ZB/B2O3) boron treated timber. DOT consumption resulted in slightly higher boron concentrations than B2O3 (324.2 and 306.3 mean ?g/g boron, respectively), and ZB 0.88% (170.0 ?g/g) was intermediate between those two treatments and the control (30.2 ?g/g). The DOT and B2O3 treatments were an order of magnitude greater than the composite board control.

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