Forecasting the global extent of invasion of the cereal pest Spodoptera frugiperda, the fall armyworm

Regan Early,Roger Day,Sean T Murphy,Pablo González-Moreno

doi:10.3897/neobiota.40.28165

Abstract

Fall armyworm, Spodopterafrugiperda, is a crop pest native to the Americas, which has invaded and spread throughout sub-Saharan Africa within two years. Recent estimates of 20–50% maize yield loss in Africa suggest severe impact on livelihoods. Fall armyworm is still infilling its potential range in Africa and could spread to other continents. In order to understand fall armyworm’s year-round, global, potential distribution, we used evidence of the effects of temperature and precipitation on fall armyworm life-history, combined with data on native and African distributions to construct Species Distribution Models (SDMs). We also investigated the strength of trade and transportation pathways that could carry fall armyworm beyond Africa. Up till now, fall armyworm has only invaded areas that have a climate similar to the native distribution, validating the use of climatic SDMs. The strongest climatic limits on fall armyworm’s year-round distribution are the coldest annual temperature and the amount of rain in the wet season. Much of sub-Saharan Africa can host year-round fall armyworm populations, but the likelihoods of colonising North Africa and seasonal migrations into Europe are hard to predict. South and Southeast Asia and Australia have climate conditions that would permit fall armyworm to invade. Current trade and transportation routes reveal Australia, China, India, Indonesia, Malaysia, Philippines and Thailand face high threat of fall armyworm invasions originating from Africa.

Highlights

We reviewed the literature of field observations and experimental studies into fall armyworm to investigate the linkages between the environment and life cycle (Figure 2, Suppl. material 1: Table S1)
Several studies found evidence that the developmental time of egg, larval, pre-pupal and pupal stages decreases with temperature up until 32–33.5 °C
Isenhour et al 1985; Simmons 1993). Survival of these stages is greatest around 25 °C, and 35 °C appears to be an upper limit on survival (Barfield and Ashley 1987; Busato et al 2005; Simmons 1993; Valdez-Torres et al 2012)

Summary

Introduction

The moth lives year-round from as far south as La Pampa, Argentina, to as far north as southern Florida and Texas, USA and undergoes seasonal migrations as far north as Québec and Ontario (Figure 1). Fall armyworm caterpillars are major pests of cereals and forage grasses and are recorded as eating 186 plant species from 42 families (Casmuz Augusto 2010). Fall armyworm is one of the most serious pests of maize in the America. Yield losses can reach 40% in Honduras (Wyckhuys and O’Neil 2006) and 72% in Argentina (Murúa et al 2006). Fall armyworm attacks many other economically important, e.g. rice, sugarcane, sorghum, beet, tomato, potato, cotton and pasture grasses (Abrahams et al 2017; Day et al 2017). Fall armyworm could pose a risk to subsistence and cash crops in large parts of the world

Methods

Results

Discussion

Conclusion