Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2007
Publication Date: 5/1/2008
Citation: Machado, V., Wunder, M., Baldissera, V.D., Oliveria, J.V., Fiuza, L.M., Nagoshi, R.N. 2008. Molecular characterization of host strains of Spodoptera frugiperda(Lepidoptera:Noctuidae)in southern Brazil.Annals of the Entomological Society of America. 101(3):619-626. :. Annals of the Entomological Society of America. 101:619-626. Interpretive Summary: Fall armyworm is an important agricultural pest of a number of crops in the western hemisphere. Two morphologically identical host strains of fall armyworm exist, the rice-strain and corn-strain, with the latter inflicting substantial economic losses in corn in both North and South America. Fall armyworm does not survive severe winters so the infestations affecting North America originate from migrants that overwinter in Florida and Texas. Scientists at the Center for Agricultural and Veterinary Entomology, Gainesville, Florida in collaboration with Brazilian colleagues used molecular methods to distinguish the corn-strain populations in these two geographically distant populations to investigate the long-range movements of this pest. The results demonstrate that it is now possible to identify the overwintering origin of migratory fall armyworm and therefore describe the annual migration patterns. A better understanding of fall armyworm populations and their movement is critical for the development of strategies to predict infestation levels and eventually control this economically important pest in the United States.
Technical Abstract: Fall armyworm infestations in most of North America north of Mexico arise from annual migrations of populations that overwinter in southern Texas and Florida. Mapping the pattern of migration and the relative contributions of the Texas and Florida populations would contribute both to our understanding of Lepidopteran migration as well as efforts to control and predict the severity of infestations by this important economic pest. A comparison of haplotype profiles within the fall armyworm corn-strain, the subgroup that preferentially infests corn and sorghum, identified significant differences in the proportions of certain haplotypes between the Texas and Florida populations. These proportional differences were preserved as the populations migrated, providing a molecular metric by which the source of a migrant population could be identified. The migratory pattern derived from this method for several southeastern states was shown to be consistent with predictions based on analysis of historical agricultural and fall armyworm infestation data. These results demonstrate the utility of haplotype proportions to monitor fall armyworm migration and also introduce a potential method to predict the severity of cotton crop infestations in the short-term.