The Effect of Temperatures and Hosts on the Life Cycle of Spodoptera frugiperda (Lepidoptera: Noctuidae)

SIMPLE SUMMARY: Fall armyworm (FAW), Spodoptera frugiperda (J E Smith) (Lepidoptera: Noctuidae) is an invasive worldwide agricultural pest that seriously threatens the safety of grain production. Temperatures and hosts play vital roles in the performance of S. frugiperda. In this study, we studied the effects of three different temperatures (20, 25, and 30 °C) and three different host plants (maize (Zea mays L. (Poaceae)), sorghum (Sorghum bicolor (L.) Moench), and coix seed (Coix lacryma-jobi L.)) on the whole life cycle of S. frugiperda. The results showed that both temperatures and host plants significantly influenced the mortality, developmental time, reproduction, and population parameters of FAW. In the treatment with host plants, the developmental period of S. frugiperda at each stage shortened significantly with the increasing of temperatures. At each temperature, the type of host plant did not affect the development time of S. frugiperda eggs. However, there was no significant difference when S. frugiperda 1st to 6th instar larvae were fed different host plants at 20 °C, while 2nd to 5th instar larvae developed rapidly on maize at 25 and 30 °C. Moreover, there were no significant differences in the longevity of FAW when fed sorghum and coix seed at 20 and 25 °C, but a significant difference in the longevity was observed at 30 °C. Feeding on maize achieved a higher intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R(0)) of S. frugiperda at 25 and 30 °C than those FAW fed on sorghum and coix seed. ABSTRACT: The interactions between ambient temperatures and host plants are central to the population dynamics of invasive animal species. Despite significant research into the effects of temperatures, the performance of invasive species is also influenced by host plants. The effects of different temperatures (20, 25, and 30 °C) and host plants (maize, sorghum, and coix seed) were tested on the mortality, development, reproduction, and population parameters of the fall armyworm (FAW), Spodoptera frugiperda (J E Smith) (Lepidoptera: Noctuidae), using an age-stage, two-sex life table. The results support the hypothesis that temperature and the species of the host plant significantly influences the performance of FAW. Feeding on maize at 30 °C resulted in a lower mortality rate, a shorter developmental time and longevity, a higher fecundity, intrinsic rate of natural increase (r), finite rate of increase (λ), and net reproductive rate (R(0)). However, at 20 °C, the host plant could eliminate temperature-mediated synergism in FAW performance, which did not reach statistical significance at 20 °C. Similar results induced by a relatively low temperature (20 °C) on different host plants were also found in the age-stage specific survival curves (s(xj)), fecundity (m(x)), maternity (l(x)m(x)), and reproductive value (v(xj)) curves of FAW. Consequently, we also need to pay more attention to FAW outbreaks on different host plants mediated by relatively low temperatures.