关键词: 甘蓝夜蛾, 变温, 发育历期, 发育起点温度, 有效积温, 种群趋势指数

Abstract:  【Aim】 This study aims to clarify the effects of fluctuating temperature on the growth, development and reproduction of the cabbage moth, Mamestra brassicae, and to explore its adaptability to environmental temperature. 【Methods】 M. brassicae eggs were bred with soybean (Glycine max) leaves and observed under five gradient fluctuating temperature ranges 13-25℃ (daily average 19℃), 16-28℃ (daily average 22℃), 19-31℃ (daily average 25℃), 22-34℃ (daily average 28℃), and 25-37℃ (daily average 31℃) in the laboratory, and the developmental duration, developmental rate, fecundity, developmental threshold temperature and effective accumulated temperature of M. brassicae at various developmental stages were measured. 【Results】 The developmental duration of M. brassicae at the fluctuating temperature range 13-25℃ was the longest, and the generation time was 65.93 d, which was significantly longer than that at the other fluctuating temperature ranges. The duration of different developmental stages decreased as the temperature increased. The developmental duration at the fluctuating temperature range 22-34℃ was the shortest, and the generation time was 38.46 d, which was significantly shorter than that at other fluctuating temperature ranges. Under the fluctuating temperatures ranging from 25℃ to 37℃, the larvae could not normally complete the individual development. In the range of daily average temperature (T) of 19-28℃ (maximum temperature difference 12℃), the developmental rate of egg, larval and pupal stages were accelerated with increasing temperature, and the fitting equations of the developmental rate (V) of each developmental stage conformed to the linear model: V_egg=0.125+0.048T, V_larva=0.023+0.012T, V_pupa=0.027+0.013T, V_adult=0.073+0.47T. The longevity of female and male adults decreased with temperature. The longevity of female and male adults at the fluctuating temperature range 13-25℃ was the longest, being 7.91 d and 8.00 d, respective, and that at the fluctuating temperature range 22-34℃ was the shortest, being  3.00 d and 3.57 d, respectively. The developmental threshold temperatures of egg, larva, pupa, and adult were 7.98, 6.54, 9.36, and 10.78℃, respectively, and the corresponding effective accumulated temperatures were 87.00, 607.36, 351.51, and 108.52 d·℃, respectively. The fluctuating temperature range 16-28℃ was more optimal for the development, survival and reproduction of M. brassicae, at which its population trend index I was 117.81. 【Conclusion】 M. brassicae is a low temperature adaptive pest and has a low ability to adapt to high temperature. The results provide a scientific basis for further studying the natural population occurrence law of M. brassicae and forecasting its occurrence period and degree.

Key words: Mamestra brassicae; fluctuating temperature, developmental duration; developmental threshold temperature, effective accumulated temperature, population trend