Combining temperature-dependent life table data into Insect Life Cycle Model to forecast fall armyworm Spodoptera frugiperda (JE Smith) distribution in maize agro- ecological zones in Africa

Abstract

The fall armyworm (FAW) Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), is an agricultural pest that recently invaded Africa. FAW has spread and established in many countries across the continent, causing huge yield losses. This study aimed to determine the relationship between temperature and the life history traits of FAW and to provide the suitable temperatures for development using life cycle modeling. Non-linear models were fitted to life table data collected at five constant temperatures of 20, 25, 28, 30, and 32 °C. The development time ranged between 0–3 days, 10–18 days, and 7–16 days for eggs, larvae, and pupae, respectively. While the optimum temperature for FAW immature stages' survival and female fecundity was predicted at a temperature range of 21–25 °C, the intrinsic rate of increase (rm) and gross reproductive rate (GRR) were significantly higher at temperatures between 25–28 °C. The model validation outcome showed similarities between observed and simulated values for development time, mortality rate, and life table parameters, attesting to the high performance of the phenology model produced. The study also explores the establishment risk index, activity index, and generation index as indicators of infestation and transmission potential of the current, 2050, 2070 climate scenarios to predict the effect of climate warming on the distribution and population dynamics of FAW. The study predicts a decrease in FAW occurrence in West Africa by 2050–2070. The results obtained could be utilized to develop management plans for FAW control that work in the different agro-ecological zones in Africa.