甜菜夜蛾的抗寒力研究

Cold hardiness of beet armyworm,Spodoptera exigua (Hiibner)

抗寒力的强弱决定了甜菜夜蛾的分布范围及越冬存活情况,并直接影响下一代的种群数量。通过测定甜菜夜蛾三个地理种群(河北隆尧、湖南衡阳和江苏南京)的过冷却点和结冰点及田间埋蛹越冬试验,以明确甜菜夜蛾的抗寒能力。研究结果表明,在各虫态中甜菜夜蛾蛹的过冷却点最低(-16.61～-15.18℃),其次为成虫、卵和幼虫。蛹的过冷却现象也最明显,因而蛹是其最适宜越冬的虫态。三个地理种群中,以湖南衡阳的抗寒能力最强,其次为河北隆尧和江苏南京。在2001和2002连续两年的田间埋蛹越冬试验表明,甜菜夜蛾的越冬死亡率均为100％。分析南京多年的冬季气温,表明某些年份甜菜夜蛾不大可能在南京越冬。因此甜菜夜蛾的常年越冬区范围应在南京以南的区域。

Cold hardiness of the beet armyworm, Spodoptera exigua （Htibner）, was investigated by measuring the supercooling points and freezing points of three geographical populations （ Longyao, Hebei Province; Hengyang, Hunan Province and Nanjing, Jiangsu Province） and the field overwintering test. The results showed that supercooling points of pupae were the lowest, followed by adults, eggs and larvae. Moreover, pupae have the most obviously supercooling phenomenon, so it was the most feasible stage for overwintering. Cold hardiness of the population from Hengyang, Hunan Province was the most powerful, followed by Longyao population （Hebei Province） and Nanjing population （Jiangsu Province）. Overwintering mortality were 100% , estimated by field trials in Nanjing with pupae burying in 2001 and 2002. And the winter temperature analysis also showed that the beet armyworm did can not survive the winter in some years. These results illustrate that the beet armyworm can possibly not overwinter in Nanjing during a chilly winter. So it is suggested that the northern limit of permanent overwintering regions for the beet armyworm be probably at the areas in the south of Nanjing.