Submitted to: Florida Entomologist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/7/2008
Publication Date: 6/11/2008
Citation: Stuhl, C.J., Meagher Jr, R.L., Nagoshi, R.N. 2008. Genetic variation in neonate behavior of fall armyworm (Lepidoptera:Noctuidae). Florida Entomologist. 91(2):151-158. Interpretive Summary: Fall armyworm larvae infest corn, forage grass, turf grass, and sorghum plantings in the southeastern United States. In Florida, fall armyworm can be a serious pest of sweet corn, field corn, and subtropical bermudagrasses. This species is composed of two strains that either infest corn or grasses, and it is known that their feeding and behavior are different. Entomologists at the Center for Medical, Agricultural and Veterinary Entomology (CMAVE), Gainesville, Florida, and an entomologist at the University of Florida, conducted laboratory experiments to compare the choices that young larvae make when searching for food. Several colonies of the two strains were collected and tested, and results showed that there were differences among the colonies in which host plant was selected. These results suggest that there is substantial variation between the two strains in selection of a host and that the young larvae are not specific in which host plants they choose.
Technical Abstract: Bioassays were developed to test plant selection of fall armyworm [Spodoptera frugiperda (J. E. Smith)] host strains to corn and stargrass. Neonate larvae from 3 corn strain and 3 rice strain colonies preferentially selected corn sections over stargrass sections in petri dish choice tests. However, whole plant-bioassays and whole plant volatile-bioassays 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 to the corn section, 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 didn’t migrate to corn. Finally, the attraction to corn was lowest in one colony where significantly more larvae moved away from corn even when it was presented first. Results in our study, along with behavioral and feeding trials from other studies, suggest that there is a consistent attraction of neonates to damaged corn but substantial variability in the strength of that attraction if they come in contact with another plant host. These differences among colonies most likely reflect genetic and phenotypic variation in wild populations.