Monday, December 11, 2006 - 8:35 AM

Differential recovery of the Formosan subterranean termite (Coptotermes formosanus Shiraki: Rhinotermitidae) after sublethal exposure to boron compounds

Margaret Gentz, kennethg@hawaii.edu1, J. Kenneth Grace, kennethg@hawaii.edu1, Mark E. Mankowski, Mark.Mankowski@borax.com2, and Julian R. Yates III, yates@hawaii.edu3. (1) University of Hawaii - Manoa, Department of Plant and Environmental Protection Sciences, 3050 Maile Way, Gilmore Hall 310, Honolulu, HI, (2) Rio Tinto Minerals (US Borax), 26877 Tourney Road, Valencia, CA, (3) University of Hawaii - Manoa, Department of Plant and Environmental Protection Sciences, 3050 Maile Way, Gilmore Hall 310, Honolulu, HI

Although boron compounds have been used since the 1800s as insecticides, their mode of action is not well understood. Borates, 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 boron compounds affect the ability of the termites to recover from sublethal exposure, termite workers (undifferentiated individuals) were collected from field colonies maintained in Honolulu, Hawai’i, and exposed to composite board samples containing different boron compounds. The treatments included zinc borate (ZB) (0.88%), disodium octaborate tetrahydrate (DOT) (60/40 ZB/DOT), anhydrous boric acid (B2O3) (60/40 ZB/B2O3), and an untreated composite board control. Termites were exposed to the boron composite boards for 5 days and subsequently exposed to untreated boards for an additional 5 days; feeding, boron ingestion, termite wet mass, and survival at day 10 were measured. Exposure to any of the borate formulations significantly decreased the amount of wood consumed and wet mass in all groups (P < 0.05), but the type of boron compound influenced the amount of boron ingested, percentage mortality, and ability to recover from exposure. The observed trend suggested that greatest mortality and least recovery occurred with B2O3 followed by DOT and ZB.

Species 1: Isoptera Rhinotermitidae Coptotermes formosanus (Formosan subterranean termite)