The Spodoptera frugiperda host strains: What they are and why they matter for understanding and controlling this global agricultural pest

Authors: Nagoshi, Rodney; Meagher, Robert - Rob

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2022
Publication Date: 12/14/2022
Citation: Nagoshi, R.N., Meagher Jr, R.L. 2022. The Spodoptera frugiperda host strains: What they are and why they matter for understanding and controlling this global agricultural pest. Journal of Economic Entomology. 115(6):1729-1743. https://doi.org/10.1093/jee/toac050.
DOI: https://doi.org/10.1093/jee/toac050

Interpretive Summary: The fall armyworm is major insect pest of corn and other crops. Originally found in the Americas fall armyworm has spread across the globe with severe outbreaks reported throughout sub-Saharan Africa and infestations found in India, southeastern Asia, and Australia. Fall armyworm is compose of two populations called host strains that differ in their preference to different plant types. Risk assessments and mitigation depend on an accurate determination of whether one or both strains are present in a given area. This manuscript reviews information known about the strains including the molecular markers used to identify strains and the degree to which the strains can hybridize with each other and potentially produce a new biotype that might pose new threats to American and global agriculture.

Technical Abstract: Fall armyworm (Spodoptera frugiperda [J.E. Smith]) is a moth native to the Western Hemisphere where it is a major pest of corn (maize) and as well as multiple other crops. It is now a global threat with its rapid dissemination in the Eastern Hemisphere. The broad host range are in part due to two subpopulations denoted as “host strains” with the C-strain preferentially impacting corn, sorghum, and cotton while the R-strain predominates in alfalfa, turf, and pasture grasses. Identifying the strains present in a location is critical to assessing what crops are at risk of infestation. However, much remains uncertain about how the strains differ and even on the fundamental issue of how they are identified. Complicating factors include the host strains are morphologically indistinguishable, the defining behavior of the strains (host plant specificity) is variable, and evidence of significant behavioral differences between geographical populations and laboratory colonies that are independent of strain identity. These factors contribute to substantial disagreements in the literature on presumptive strain differences. This paper presents our perspectives of the strains and the criteria that should be met to conclude that a particular trait is “strain-specific”. The intent is to facilitate a common understanding of what the strains represent and to develop a more consistent experimental framework for studies on strain behaviors. Evidence is summarized that support a primary role for Z-linked genes in strain identity, which has potential implications for whole genome approaches to define strains and provide a different perspective on the mechanisms driving strain divergence.