Assessing the use of wing morphometrics to identify fall armyworm (Lepidoptera: Noctuidae) host strains in field collections

Authors: NAGOSHI, KIRA - University Of Florida; Allan, Sandra - Sandy; Meagher, Robert - Rob

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2019
Publication Date: 12/27/2019
Citation: Nagoshi, K.I., Allan, S.A., Meagher Jr, R.L. 2019. Assessing the use of wing morphometrics to identify fall armyworm (Lepidoptera: Noctuidae) host strains in field collections. Journal of Economic Entomology. 113(2):800-807. https://doi.org/10.1093/jee/toz344.
DOI: https://doi.org/10.1093/jee/toz344

Interpretive Summary: The fall armyworm, as a primary pest of corn in southeastern US, the Caribbean, South America and more recently in Africa, is comprised of two subpopulations known as rice and corn strains. These differ in host plant preferences as well as with biological traits and geographical distributions. Understanding the distribution and behaviors of these two strains is crucial to the management of this pest. Use of molecular markers for identifying strains of individual moths is effective, however is expensive and requires time. In this study, scientists at USDA/ARS, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, examined moths captured in different crops to determine the relationship between host plant strain verified by molecular markers, host plants and morphological wing traits. While some morphological differences in wings were observed between host strains, the actual host plant was more important in determining morphological differences. These results confirm the importance of molecular typing for strain identification of this species.

Technical Abstract: The fall armyworm (Spodoptera frugiperda) (J. E. Smith) is a major pest of maize, sorghum, and cotton in the Western Hemisphere and has recently become established in parts of Africa and Asia. The species is capable of developing on of over 80 host plant species and thus has the potential of causing economic harm on a number of crops. A major contributor to this host range are two subpopulations historically called host strains that differ in their host specificity. Understanding the distribution and behaviors of these two strains is crucial to the management of this pest. A major difficulty in such studies is that the two strains have long been considered morphologically indistinguishable, with molecular markers the only reliable means of identification. Studies of fall armyworm in Colombia reported strain differences in wing morphology that potentially provide an alternative means of strain identification. This study tested whether a similar phenotypic difference was present in Florida populations using geometric morphometric analysis of 15 anatomical landmarks on the forewings of 182 specimens from three habitats associated with different host plants. Significant differences in wing size and shape were found between habitats and between strains, but not between strains within the same habitat. The data indicate that strain differences in wing phenotype are a secondary consequence of strain-biased host choice and therefore probably not a reliable indicator of strain identity in field populations.