Characterization of Slow-acting Insecticides for the Remedial Control of the Formosan Subterranean Termite (Isoptera: Rhinotermitidae)

Abstract

We describe a method to examine time trends in mortality of the Formosan subterranean termite, Coptotermes formosanus Shiraki, exposed to insecticides. Slow-acting toxicants required a longer time to kill termites at low concentrations than at high concentrations. The level of mortality and the speed of death were dependent on concentration. With acute toxicants, the time required to kill termites was similar at high or low concentrations, while the mortality levels were concentration-dependent. This speed of death at various concentrations of an insecticide can be quantified for comparison purposes using the proposed effective lethal time 90% (ELT90), defined as the amount of time required for an insecticide to kill 90% of the treated individuals within a maximum 14-day span. Slow-acting toxicants were characterized by ELT90 values that spanned a broad range of time, while acute toxicants exhibited a narrow range of ELT90 values.