Mortality Time Trends of Three Subterranean Termite Species When Exposed to 20-Hydroxyecdysone, Alone and in Combination With Noviflumuron.

Workers of three termite species, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), Coptotermes gestroi (Wasmann) (Blattodea: Rhinotermitidae), and Reticulitermes flavipes (Kollar) (Blattodea: Rhinotermitidae), were force-fed with cellulose media pads treated with 20-hydroxyecdysone (20E) alone and in combination with noviflumuron for 3 d to examine their mortality time trends up to 14 d (including 3-d exposure time). Termites exhibited symptoms of hyperecdysonism before the onset of death. The times required for 20E to fully express its effects were 10-13 d for C. formosanus, 13-14 d for C. gestroi, and 11-13 d for R. flavipes. Higher 20E concentrations resulted in higher mortalities at 14 d, and the addition of noviflumuron generally yielded higher mortalities. The lethal time of 20E was similar to chitin synthesis inhibitors such as noviflumuron than metabolic inhibitors, and the 10-14 d lethal time may be sufficient for 20E-affected termites to return to the central nest before the onset of hyperecdysonism and ultimate death. As an active ingredient in baiting systems, 20E has shown potential to reduce the colony elimination time.