Influence of low temperature on lethal time extension for different life stages of Cryptolestes ferrugineus (Stephens) with strong resistance to phosphine fumigation

Knowing the time extension degree of full mortality in phosphine fumigation at low temperature significantly contributes to successful insect pest control, especially for reducing fumigation failure and inhibiting resistance development. The comparison of mortality and lethal time on eggs, larvae, pupae and adults of Cryptolestes ferrugineus (Stephens) was conducted, and the strain with 1043 times of resistance factor to phosphine was assayed during fumigation with 300 mL/m3 of phosphine concentration at 18, 23 and 28 °C. The LT50 values to eggs, larvae, pupae and adults of C. ferrugineus at 18 °C were postponed by 2, 2, 1 and 5 d compared with that at 23 °C, and 5, 4, 5 and 7 d compared with that at 28 °C, respectively. The LT99 values to eggs, larvae, pupae and adults at 18 °C were 5, 1, 2 and 7 d longer than that at 23 °C, and 6, 5, 5 and 10 d longer than that at 28 °C, respectively. The lethal time of different life stages of the C. ferrugineus strain significantly increased with temperature decreasing. The exposure time of full mortality on pupae at 300 mL/m3 of phosphine at 18 °C reached 38 d, which was 12 d longer than that of larvae. The order of tolerance of different life stages of C. ferrugineus exposed to 300 mL/m3 phosphine from high to low was pupae, eggs, adults, larvae at tested temperatures.