Abstract
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.
Highlights
Rhinotermids construct, dwell, and forage for food in extensive and labyrinthine underground galleries, which renders a complete and uniform application of insecticides impractical [1]
LT50 values ranged from 0.96 to 98.8 h for eastern subterranean termites exposed to 5.0 ppm at 28 ◦ C and Formosan subterranean termites exposed to 0.5 ppm at 16 ◦ C (Tables 1 and 2)
LT50 values declined with increasing concentrations and temperatures for both eastern (Table 1) and Formosan (Table 2) subterranean termites
Summary
Rhinotermids construct, dwell, and forage for food in extensive and labyrinthine underground galleries, which renders a complete and uniform application of insecticides impractical [1]. The popular termite products currently used in the United States utilize non-repellent insecticides. Used products are liquid, powder, granule, or foam formulations, as well as baits. Their non-repellent nature permits unknowing exposure and their slow-acting characteristics allow ample time and opportunity for termites to transfer these compounds between contaminated and naïve colony-mates through social interactions such as grooming, trophollaxis, and caregiving [2,3]. The cascading nature of this social route of distribution increases the coverage of non-repellent compounds to areas far removed from the point of application [4,5]. There are two currently EPA (USA Environmental Protection Agency) registered products containing the non-repellent active ingredients fipronil and indoxacarb, but the effect of temperature on soil termiticide performance has not been investigated
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