低温对沙葱萤叶甲越冬卵存活和发育的影响

【目的】沙葱萤叶甲Galeruca daurica(Joannis)是近年来在内蒙古草原暴发成灾的一种新害虫,以卵在牛粪、石块及草丛下越冬,了解其越冬卵的抗寒能力有助于预测其分布范围及种群数量动态。【方法】在室内测定了沙葱萤叶甲越冬卵在不同低温条件下(-18~-39℃)暴露12和24 h及在-30℃低温条件下暴露不同时间(0~60 d)的存活率以及存活卵的发育历期。【结果】低温强度和暴露时间对沙葱萤叶甲越冬卵的存活率有显著影响,随着温度的降低和暴露时间的延长,越冬卵的存活率降低。当温度≤-33℃暴露12 h或≤-30℃暴露24 h,越冬卵存活率显著低于其相应的对照(25℃)。越冬卵低温暴露12和24 h的致死中温度(LT50)分别为-33.08和-32.13℃,在-30℃下的致死中时间(Lt50)为33.33 d。经-36℃低温暴露12 h或≤-33℃低温暴露24 h后,存活的越冬卵发育历期显著延长,而-30℃低温暴露30 d内差异不显著。【结论】沙葱萤叶甲越冬卵抗寒能力强,冬季低温通常不会造成越冬卵的大量死亡。

Effects of low temperature on the survivorship and development of overwintering eggs of Galeruca daurica (Coleoptera: Chrysomelidae)

【Aim】 Galeruca daurica (Joannis) is a new pest outbreaking seriously in the Inner Mongolian grasslands in recent years and overwinters as eggs under cow pats, stones and grass clusters. Understanding the cold hardiness of the overwintering eggs of G. daurica is helpful to forecast its distribution and population dynamics. 【Methods】 We measured the survival rates and developmental durations of overwintering eggs of G. daurica exposed to different low temperatures (-18--39℃) for 12 and 24 h and exposed to -30℃ for different periods (0-60 d), respectively, in the laboratory. 【Results】 Low temperature intensity and exposure time significantly affected the survival rates of overwintering eggs of G. daurica. The survival rates declined with the decrease of exposure temperature and the extension of exposure time. After the overwintering eggs were exposed to the temperatures ≤-33℃ for 12 h or the temperatures ≤-30℃ for 24 h, their survival rates were significantly lower than the corresponding controls (25℃). The lower half lethal temperatures (LT₅₀) after 12 and 24 h exposure were -33.08 and -32.13℃, respectively, and the half lethal time (Lt₅₀) at -30℃ was 33.33 d. The developmental duration of surviving eggs prolonged significantly after exposure to -36℃ for 12 h or the temperatures ≤-33℃ for 24 h, but had no significant change after exposure to -30℃ for 30 days. 【Conclusion】 The overwintering eggs of G. daurica have strong cold hardiness, and low temperature in winter may usually not cause mass mortality of overwintering eggs.