Laboratory Evaluation of Two Chitin Synthesis Inhibitors, Hexaflumuron and Diflubenzuron, as Bait Toxicants Against Formosan and Eastern Subterranean Termites (Isoptera: Rhinotermitidae)

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Two chitin synthesis inhibitors, hexaflumuron and diflubenzuron, were evaluated in a laboratory choice test for their potential as bait toxicants against the Formosan subterranean termite, Coptotermes formosanus Shiraki, and the eastern subterranean termite, Reticulitermes flavipes (Kollar). Concentrations of hexaflumuron that elicited feeding deterrence were >125 ppm for C. formosanus and >62.5 ppm for R. flavipes , whereas concentrations required to cause >90% mortality at 9 wk were > 15.6 ppm and >2 ppm for C. formosanus and R. flavipes , respectively. Diflubenzuron deterred feeding of C. formosanus at such low concentrations (>2 ppm) that the highest recorded mortality was only 50% and is not likely to be effective in a bait against this termite species. More than 80% of R. flavipes workers died after feeding on diflubenzuron at >7.8 ppm, whereas feeding deterrence was recorded at >31.3 ppm. We conclude that hexaflumuron is superior to diflubenzuron as a bait toxicant because it is effective over a concentration range of 15.6-62.5 ppm. This concentration range is lethal and nondeterrent for both C. formosanus and R. flavipes . Diflubenzuron is efficacious against R. flavipes over a fairly narrow range of concentrations (7.8-31.3 ppm) and does not appear to be useful as a bait toxicant against C. formosanus .