Effects of soil moistures and pupal chamber on overwintering of Spodoptera exigua
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Key Words： Spodoptera exigua,pupae,soil moisture,pupal chamber,overwintering
Abstract：Effects of soil moisture and pupal chamber characteristics on the overwintering of Spodoptera exigua Hübner were studied in the field in Wuhan District.S.exigua pupae could survive more than 30 days in natural pupal chambers.After 15 days the survival rate of pupae exposed to high,moderate and low soil moisture levels decreased to 80%,20% and 43% respectively.No pupae survived longer than 60 days.Extension of the treatment time over 60 days caused pupae to blacken,swell and decay until only a residual puparium remained.The pupal supercooling point (SCP),freezing point (FP) and body water content (BWC) differed significantly between the three different soil moisture levels (P ≤ 0.05).SCP,FP and BWC were the lowest (-20.2±1.1) ℃,（-11.95±2.5）℃ and (57.6±7.7) % respectively at the lowest soil moisture level.The pupal chamber evidently provides essential protection required for pupae to overwinter in field.