Temperature-Mediated Variations in Behavior and Mortality Caused by Non-Repellent Insecticides in Subterranean Termites (Blattodea: Rhinotermitidae).

Behavioral symptoms and mortality associated with intoxication with insecticides fipronil and indoxacarb were determined in field-collected eastern subterranean termites, Reticulitermes flavipes (Kollar), and Formosan subterranean termites, Coptotermes formosanus Shiraki. Behaviors and mortality were evaluated at three temperatures (16, 22, and 28 °C) and three concentrations of fipronil (0.5, 1, and 5 ppm) and indoxacarb (50, 75, and 100 ppm). LT50 (median lethal time to kill 50% of the termites) values declined with increasing concentrations and temperatures for both fipronil-exposed eastern and Formosan subterranean termites, whereas these values were not always the highest at 16 °C for indoxacarb-treated termites. The greatest change (reduction) in LT50 values occurred for both species between 16 and 22 °C at the lowest concentration of each insecticide. Intoxication and moribundity were the most frequently observed behaviors for fipronil-exposed termites, whereas intoxication, ataxia, and moribundity were observed for most concentration and temperature combinations for indoxacarb-exposed termites. The inherent toxicity of fipronil was higher than that of indoxacarb. The higher presence and duration of intoxication behaviors may positively affect the performance of indoxacarb against subterranean termite colonies.

Effects of non-repellent termiticides on the tunneling and walking ability of the eastern subterranean termite (Isoptera: Rhinotermitidae).

BACKGROUND: Non-repellent insecticides, including fipronil and indoxacarb, are becoming increasingly important for soil treatments to manage the eastern subterranean termite, Reticulitermes flavipes (Kollar). The effects of these insecticides on termite walking and tunneling behavior could significantly reduce their efficacy against colonies. RESULTS: Groups of R. flavipes were exposed to several concentrations of commercial formulations of fipronil and indoxacarb, and the ability of treated termites to tunnel in soil and walk was assessed. Increasing insecticide concentration resulted in a reduction in the ability of R. flavipes to walk, tunnel and form tunnel branches; the importance of these effects on the use of non-repellent insecticides is discussed. CONCLUSION: Exposure of R. flavipes to 1, 10 or 50 mg L(-1) of fipronil or 50, 100 or 200 mg L(-1) of indoxacarb significantly reduced termite walking and tunneling and the number of tunnel branches. Distance walked (ca 73 mm) by untreated control termites did not change over time for at least 16 h after treatment; control termites formed ca 150 cm of tunnels with ca 40 branches.

Effects of indoxacarb concentration and exposure time on onset of abnormal behaviors, morbundity, and death in eastern subterranean termite (Isoptera: Rhinotermitidae).

Onset of abnormal behaviors, morbundity, and death was evaluated in eastern subterranean termites, Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae), exposed to several concentrations (45, 90, 135, and 180 ppm) of indoxacarb and to several (5, 10, 20, 40, 80, and 160 min) exposure periods. Abnormal behaviors, morbundity, and death occurred in a predictable sequence: disorientation, ataxia, and morbundity followed by death. In general, higher concentrations and longer exposure periods resulted in faster onset of abnormal behaviors, morbundity, and death. The average onset time of abnormal behaviors, morbundity, and death was faster for groups of termites compared with individuals exposed to similar concentrations and periods of contact. The importance of onset times of abnormal behaviors as another important measure of the toxicity of slow-acting toxicants is discussed.