Demographic Characteristics and Population Simulation of Newly Invasive Fall Armyworm on Arachis hypogaea (Fabales: Fabaceae) and Dominant Green Manure Plant in Taiwan.

Spodoptera frugiperda (J.E. Smith) is a severe and fast-spreading pest of numerous agro-economic crops, including miscellaneous, vegetables, and green manure crops. Understanding pest ecology represents a core component in integrated pest management decision-making. In Taiwan, peanut (Arachis hypogaea L.) is an important miscellaneous crop, whereas sesbania (Sesbania roxburghii Merr.) is the most frequently used green manure crop. To improve the S. frugiperda management in Taiwan, the demographic characteristics and population simulation of this pest reared on peanut and sesbania leaves were analyzed using the age-stage, two-sex life table theory. The intrinsic rate of increase, finite rate of increase, and net reproductive rate of S. frugiperda were higher when reared on peanut (0.1625 d-1, 1.1764 d-1, 264.9 offspring) than on sesbania (0.0951 d-1, 1.0997 d-1, and 30.3 offspring). Population projection of S. frugiperda on peanut demonstrated that this crop is a more suitable host plant than sesbania. Yet, this suboptimal host still assures an increasing trend of more than 357-fold individuals in 75 d, from the initial cohort of 10 eggs. Our data suggest that green manure plants in fallowing fields may support the pest's survival all year round, and may be responsible for a successful establishment and unexpected outbreaks of this invasive pest on the neighboring crops in Taiwan. Our study thus highlights the importance of assessing the population dynamics and areawide pest management of an invasive polyphagous pest on a noneconomic crop to mitigate the potential risk of reinfestation and thus outbreaks.