Degradation and residual efficacy of beta-cyfluthrin as a surface treatment for control of Tribolium castaneum Herbst: Effects of temperature and environment

Abstract

Concrete arenas were treated with the low and high label rates of beta-cyfluthrin Tempo SC Ultra® (10 and 20 mg Active Ingredient [AI]/m2, respectively) and stored during the summer and autumn in two separate years inside an empty grain bin, inside a rice mill, and inside a laboratory at an approximate ambient temperature of 27 °C. Bioassays were conducted by removing the arenas at 0 (1 day) to 10 weeks post-treatment from the three locations where they were stored, and exposing adults of Tribolium castaneum (Herbst), the red flour beetle, for 0.5–3 h on the arenas. Rapidity of knockdown was used to assess residual efficacy. Application rate was significant (P < 0.05) for rapidity of knockdown for the summer storage period but not for autumn (P ≥ 0.05). As the weeks progressed during summer, knockdown was progressively slower during the 0.5 to 3-h exposure period on arenas held inside the grain bin compared to the arenas inside the rice mill and the laboratory. During autumn the order was reversed for the grain bin and laboratory as the weeks progressed but at 10 weeks knockdown after 3 h was still much less on arenas held inside the bin and mill compared to the laboratory. Extreme high temperatures in the grain bin during the summer, and the fluctuating temperatures during autumn, may have promoted residual degradation on arenas held in the bin and mill compared to the constant temperatures in the laboratory. Results show that residual persistence of contact insecticides for control of stored product insects may be less on treated surfaces outside of a laboratory setting, and caution is warranted when predicting time periods for residual efficacy in sites that are outside of research laboratories with stable environmental conditions.