Genetic Variation in Neonate Behavior of Fall Armyworm (Lepidoptera: Noctuidae)

Abstract

Bioassays were developed to test plant selection of fall armyworm (Spodoptera frugiperda (J. E. Smith)) host strains to corn (Zea mays L.) and stargrass, a forage grass closely related to bermudagrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis). Neonate larvae from 3 corn strain and 3 rice strain colonies preferentially selected corn over stargrass in petri dish choice tests. However, bioassays of whole plants and whole plant volatiles showed that selection of a particular host was not clear and there were no significant differences in plant choice. Two additional bioassays were conducted to determine if larvae would continue to disperse once they came in contact with a plant source. One colony was always biased towards corn regardless of which plant was encountered first. For 4 colonies, the attraction to corn was reduced such that when stargrass was first contacted, equal or greater numbers of larvae stayed and did not migrate to corn. Finally, the attraction to corn was lowest in 1 colony in which significantly more larvae moved away from corn even when it was presented first. Results of our study, along with behavioral and feeding trials from other studies, suggest that there is a consistent attraction of neonates to damaged corn regardless of “strain” designation, but substantial variability in the strength of that attraction if they come in contact with another plant host first. These differences among colonies most likely reflect genetic and phenotypic variation in wild populations. More information at http://www.ars.usda.gov/pandp/people/people.htm?personid=11809

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