《环境昆虫学报》

为明确草地贪夜蛾Spodoptera frugiperda的耐寒能力，本研究测定了不同低温条件下（恒温和波动低温）草地贪夜蛾幼虫和蛹的存活情况，为预测该害虫的越冬分布区提供科学依据。恒温试验以3龄和5龄幼虫为研究对象，在0℃、?2℃、?5℃、?10℃低温下进行短期低温胁迫，分别统计处理0.5、1、2、3、6、12、24和36 h时的死亡率；同时选取4日龄蛹为研究对象，在6℃和10℃条件下处理3 d和5 d，观测蛹的羽化率。波动低温试验在6℃、10℃的基础温度上，设置±2℃、±4℃和±6℃的昼夜温差，对5龄幼虫和4日龄蛹分别进行0、5、10、15、20、25和30 d胁迫处理，统计幼虫死亡率、化蛹率和蛹的羽化率。结果显示，在短期低温胁迫下，随处理温度的降低和时间的延长，幼虫和蛹的死亡率逐渐上升。在36 h后，0℃条件下的幼虫可全部存活，而?5℃、?10℃条件下的幼虫全部死亡。蛹在恒定6℃和10℃处理下可正常羽化，但随低温时间的延长，其羽化率降低。在长期波动低温条件下，5龄幼虫在10℃波动低温条件下可存活30 d，死亡率为21.0%~57.0%；在6℃波动低温条件下，幼虫存活天数为21 d，而蛹在波动低温处理下均无法正常羽化。综合表明，草地贪夜蛾种群可在6℃~10℃范围内以5龄幼虫和蛹越冬，但在低于6℃的区域无法存活。本文结果为草地贪夜蛾的分布扩散趋势预测及防控策略提供了科学依据。

英文摘要:

We determine cold tolerance of Spodoptera frugiperda (Fall Armyworm) by assessing the survival of larvae and pupae under different low-temperature regimes. Our aim was to better predict the overwintering distribution of this pest. The test adopts the method of combining constant temperature and variable temperature. Constant lower temperature experiments were conducted to understand the mortality of larvae firstly. The 3th and 5th instar larvae of S. frugiperda were exposured at 0°C, ?2°C, ?5°C, and ?10°C for durations of 0.5, 1, 2, 3, 6, 12, 24, and 36 hours, corresponding (called short-term low-temperature experiment). Moreover, the emergence rate and mortality were observed after pupae with 4 days-age exposed at 6°C and 10°C for 3 and 5 days. Another fluctuating temperature experiment was carried out for test the cold tolerance of 5th instar larvae and 4-day-old pupae. Daily temperature was controlled at 6°C and 10°C with diurnal temperature fluctuation of ±2°C, ±4°C, and ±6°C. Mortality, pupation and emergence were recorded in different days (from 0 to 30 days, interval 5 days). Under short-term low-temperature exposure, mortality of larvae and pupae increased with the decreasing temperature and duration of exposure. After 36 hours, larvae survived at 0°C but all died at ?5°C and ?10°C. Pupae could emerge normally under constant temperatures of 6°C and 10°C, but the emergence rate decreased with duration of low-temperature exposure. Under long-term fluctuating low-temperature conditions, 5th instar larvae survived for 30 days at 10°C with a mortality rate ranging from 21% to 57%. At 6°C, larvae survived for 21 days, but pupae failed to emerge under any fluctuating temperature treatment. The study showed that under short-term (36 hours) exposure at 0°C, the larvae of S. frugiperda were not affected. When the fluctuating temperature was 6°C, larvae could survive for a longer period. Temperature fluctuations impose greater risk stressing on survival of insect pests. It is suggested that S. frugiperda populations may overwinter as 5th instar larvae in natural environments within the 6°C to 10°C range, but will not survive in regions with temperatures below 6°C. The results of this study provide a scientific basis for predicting the distribution and diffusion trend of S. frugiperda and the prevention and control strategies.

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