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Influence of Temperature on Toxicity of Propylene Oxide at Low Pressure Against Tribolium castaneum

A.A. Isikber, 1,* S. Navarro,2 S. Finkelman,2 M. Rindner2 and R. Dias2

Abstract: Toxicity of propylene oxide (PPO) at low pressure against the most common stored-product insect, Tribolium castaneum (Herbst), over a short exposure time, was tested at three different temperatures (16º, 22º and 30ºC). Toxicities of PPO at 100 mm Hg were strongly influenced by ambient temperature. LD50 and LD99 toxicities ranged from 4.7 to 28.9 mg l-1 and from 10.5 to 72.6 mg l-1 respectively, showing that susceptibility was positively correlated to the temperature. The LD99 values for all life stages (except the larval stage) were significantly lower at 30º than those at 16º and 22ºC. However, the LD99 values for all life stages (except the pupal stage) at 16º were not significantly different from those at 22ºC. A concentration × time (Ct) product of 291, 171 and 98 mg h/l was required to obtain complete mortality (99%) of T. castaneum at 16º, 22º and 30ºC, respectively. Thus, the efficacy of PPO at 100 mm Hg to all life stages of T. castaneum also decreased as the temperature decreased from 30º to 16ºC.

Key words: Propylene oxide; fumigant; toxicity; temperature; Tribolium castaneum.

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