The relative humidity was maintained above 75% by placing a dish containing 100mL of aqueous glycerol solution at the bottom of the desiccator beneath a metal grid (Beckettet al., 2010). The desiccators with insects were first conditioned at 5 ◦C in a temperature-regulated container for up to 2 h, and then injected with PH3 using a gas-tight syringe and immediately sealed for fumigation (Liu et al., 2010). At the end of fumigation, the desiccators with insects were opened for aeration for 1 h. The number of total eggs in petri dishes were first examined under a stereoscopic microscope magnifying 30 times and then used for fumigation. Eggs that hatched after fumigation were calculated by examining larvae hatched 2 d after fumigation and individuals were considered dead when 1st instars showed no response to a probe