| The fall armyworm, Spodoptera frugiperda (J. E. Smith), invaded Shandong Province in June in 2019 and then infested maize in many areas, posing a great threat to Zea mays L. production. The effects of temperatures on the growth and survival of S. frugiperda in Shandong Province were studied, and the developmental zeros and the effective accumulative temperatures of the pest were determined, the number of occurrence generations of S. frugiperda in five representative regions was predicted. All the research provided theoretical basis for monitoring, prediction and scientific control of the pest. S. frugiperda larvae fed with fresh maize kernels were reared at constant series temperatures (15, 18, 21, 24, 27, 30℃) in the laboratory.The durations and survival rates of different developmental stages were observed. The developmental zeros and effective accumulative temperatures of S. frugiperda at each stage/instar and the whole generations were determined by the linear regression method and the direct optimal method, and theoretical number of generations was calculated according to the meteorological data in Shandong Province. From 15℃ to 30℃, the developmental durations of each stage and whole generations were significantly shortened with the increase of temperatures. At 15℃, the mortality rates of larvae and pupae were 22.57% and 85.71%; at 18℃, the mortality rates of larvae and pupae were 21.09% and 23.19% respectively. The mortalities of preadults (from eggs to pupae) were 97.37% at 15℃ and 51.82% at 18℃. According to the linear regression method, the developmental zeros of eggs, larvae, pupae, whole generations were 14.16, 14.00, 14.77, 12.72℃, respectively and the effective accumulative temperatures were 38.21, 155.42, 114.36, 523.33 day·degree, respectively; Based on the direct optimization method, the developmental zeros of eggs, larvae, pupae, whole generation were 13.41, 14.39, 15.12, 13.30℃, respectively and the effective accumulative temperatures were 41.96, 149.20, 110.47, 497.78 day·degree, respectively. According to the developmental zeros and the effective accumulative temperatures from five representative regions of Shandong Province, the theoretical number of annual generations in five representative regions was calculated, which was 3.6~3.9 generations in Northern Shandong, 3.5~3.7 generations in Southern Shandong, 3.5~3.8 generations in Central Shandong, 3.2~3.5 generations in Western Shandong and 2.5~3.4 generation in Jiaodong Peninsula (Eastern Shandong). The results showed that the suitable temperature range for the growth and survival of S. frugiperda was 24~30℃; the theoretical number of generations of S. frugiperda in Shandong were roughly divided into 2.5~3.5 generations in Jiaodong Peninsula, 3.0~3.5 generations in Western Shandong, and 3.5~4.0 generations in Central, Southern and Northern Shandong. |
