Title: Geographic variation in sexual attraction of Spodoptera frugiperda corn- and rice-strain males to pheromone lures Authors
|Unbehend, Melanie -|
|Hanniger, Sabine -|
|Vasquez, Gissella -|
|Juarez, Maria -|
|Reisig, Dominic -|
|Mcneil, Jeremy -|
|Heckel, David -|
|Groot, Astrid -|
Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 17, 2014
Publication Date: N/A
Interpretive Summary: The migratory pest fall armyworm (Spodoptera frugiperda) attacks corn, cotton, grasses, and rice in North and South America and in the Caribbean. The species is composed of two host strains that feed primarily on corn and other large grasses, or rice and other small grasses. Biological and behavioral differences exist between the strains. One behavior difference that could be important for sweet corn producers in the US is the composition of the female-produced pheromone, since that is the chemical that is used in traps to monitor populations. Scientists in Europe, South America, the Caribbean, and a scientist at the USDA Agriculture Reserach Service, Center for Medical, Veterinary and Agricultural Entomology in Gainesville, Florida, collaborated on a project to test male’s response to the different chemical pheromone blends that might be produced by either corn- or rice-strain females. Results showed that corn- and rice-strain males showed geographic rather than strain differences in their response. Therefore, monitoring in agricultural fields can be improved by determining the pheromone components of females in a broad geographical area.
Technical Abstract: The corn- and rice-strains of Spodoptera frugiperda exhibit several genetic and behavioral differences and appear to be undergoing ecological speciation in sympatry. Previous studies reported conflicting results when investigating male attraction to pheromone lures in different regions, but this could have been due to inter-strain and/or geographic differences. Therefore, we investigated whether corn- and rice-strain males differed in their response to different synthetic pheromone blends in different regions in North America, the Caribbean and South America. All trapped males were strain-typed by two strain-specific mitochondrial DNA markers. In the first experiment, we found a nearly similar response of corn- and rice-strain males to two different 4-component blends, resembling the corn- and rice-strain female blend we previously described from females in Florida. This response showed some geographic variation in fields in Canada, North Carolina, Florida, Puerto Rico, and South America (Peru, Argentina). In dose-response experiments with the critical secondary sex pheromone component (Z)-7-dodecenyl acetate (Z7-12:OAc), we found some strain-specific differences in male attraction. While the response to Z7-12:OAc varied geographically in the corn-strain, rice-strain males showed almost no variation. We also found that the minor compound (Z)-11-hexadecenyl acetate (Z11-16:OAc) did not increase attraction of both strains in Florida and of corn-strain males in Peru. In a fourth experiment, where we added the stereo-isomer of the critical sex pheromone component, (E)-7-dodecenyl acetate, to the major pheromone component (Z)-9-tetradecenyl acetate (Z9-14:OAc), we found that this compound was attractive to males in North Carolina, but not to males in Peru. Overall, our results suggest that both strains show rather geographic than strain-specific differences in their response to pheromone lures, and that regional sexual communication differences might cause geographic differentiation between populations.