Concentration-Dependent Presoldier Induction and Feeding Deterrency: Potential of Two Insect Growth Regulators for Remedial Control of the Formosan Subterranean Termite (Isoptera: Rhinotermitidae)

Abstract

Laboratory experimental groups of 120 workers and 30 soldiers of Coptotermes formosanus Shiraki were given a choice of feeding on untreated pine blocks or pine blocks treated with one of five concentrations of methoprene (0, 4, 20, 100, and 500 ppm) or S-31183 (2-[1-methyl-2(4-phenoxy-phenoxy)ethoxy]pyridine) (0, 20, 100, 500, and 2,500 ppm) for 4, 8, or 12 wk. Soldier production and total mortality were significantly increased by 100 and 500 ppm methoprene at 8 and 12 wk. Biologically significant mortality (>50%) resulted from feeding on blocks treated with methoprene at 500 ppm after 8 wk. The response of C. formosan us to S-31183 was much reduced when compared with the response to methoprene. None of the concentrations of 5-31183 caused biologically significant mortality to the C. formosan us groups. In addition, the highest concentration of 5-31183 caused feeding deterrency that was apparently learned. Effective baits for remedial control of C. formosanus colonies should be evaluated under conditions that simulate actual use. These baits would require methoprene concentrations from 500 to 1,500 ppm, depending on the pattern of use.