Submitted to: Florida Entomologist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/1/2008
Publication Date: 12/1/2008
Citation: Nagoshi, R.N., Meagher Jr, R.L. 2008. Review of fall armyworm (Lepidoptera: Noctuidae) genetic complexity and migration. Florida Entomologist. 91(4):546-554. Interpretive Summary: Spodoptera frugiperda (J.E. Smith; Lepidoptera: Noctuidae) or fall armyworm is an important agricultural pest 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. Scientists at the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology, Gainesville, FL, reviewed recent studies our laboratory and others investigating the population genetics and migration patterns of fall armyworm. One objective is to identify the overwintering sources of the migratory populations infesting crops in the United States and Canada, information that will be used to develop methods for predicting long-range movements and mitigating populations prior to migration. A second goal is to understand the genetic basis for the broad host range exhibited by this species.
Technical Abstract: The fall armyworm, Spodoptera frugiperda (J. E. Smith) is a significant economic pest in the western hemisphere, causing substantial losses in corn, sorghum, forage and turf grasses (Luginbill 1928, Sparks 1979). Although fall armyworm does not survive severe winters, it infests most of the central and eastern United States and Canada because of annual migrations from overwintering sites in Florida and Texas (Barfield et al. 1980). A detailed description of these movements is a prerequisite for identifying the factors that determine the timing and direction of migration and for developing models that can predict the severity of infestations at the migratory destinations. Complicating this effort is the genetic heterogeneity within the species, which increases phenotypic variability. Particularly important is the observation of two “host strains”, defined by a preferential association with either large grasses (designated corn-strain), such as corn and sorghum, or smaller grasses (designated rice-strain), such as rice and bermudagrass (Pashley et al. 1985, Pashley 1986, Pashley et al. 1987b, Pashley 1988a). This paper reviews recent studies examining the genetic complexity of fall armyworm populations, including the characteristics of the two strains and the possibility of subgroups within strains. The use of this information to monitor short and long distance movements is described.