Title: Attraction of fall armyworm males (Lepidoptera: Noctuidae) to host strain females Authors
Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 7, 2013
Publication Date: August 1, 2013
Citation: Meagher Jr, R.L., Nagoshi, R.N. 2013. Attraction of fall armyworm males (Lepidoptera: noctuidae) to host strain females. Environmental Entomology. 42(4):751-757. Interpretive Summary: Fall armyworm is a moth pest that attacks many agricultural crops such as corn, sorghum, pasture and turf grasses, rice, cotton, peanuts, and sugarcane. The species is composed of two types or host strains, one that feed mostly on large grasses and cotton (corn strain) and one that feeds on small grasses (rice strain). However, both host strains can be in the same area and can attack the same crops at the same time. Since the host strains can hybridize, researchers have tried to determine how the two host strains keep their individual characteristics. One possible method is for the females to release different pheromone blends that attract only males of their own host strain. Scientists at the USDA-Agriculture Research Service, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, tested commercial pheromone lures and virgin females of both host strains (corn strain and rice strain) in different agricultural habitats in Florida. The host strain of responding males was then determined. Results suggested that almost 60% of the males that were attracted to the pheromone lures were corn strain. Female moths attracted higher numbers of rice strain males, but corn and rice strain males were attracted more to corn strain females than rice strain females. It appears that the small differences in pheromone attraction are not enough to keep the host strains from intermating.
Technical Abstract: Attraction of wild male fall armyworm, Spodoptera frugiperda (J. E. Smith), was compared in trapping experiments during 2005 – 2009 in Florida. Traps were baited either with a commercial sex pheromone lure or corn and rice strain females obtained from laboratory colonies. Over 7400 male moths were collected, and a large subset (> 1500) of these moths was analyzed for their host strain identity. The pheromone lure attracted over 4 times more males than virgin corn or rice strain females. Almost 60% of males attracted to the pheromone lure were identified as corn strain. However, both corn and rice strain females attracted a higher percentage of rice strain males, providing evidence that the commercial lure used in our study is biased to attract corn strain males and underestimates rice strain population numbers relative to corn strain numbers. Corn and rice strain males were attracted more to corn strain females than rice strain females, although there was variation in response according to season. Our results suggest that attraction of males to corresponding-strain females does not appear to be a pre-mating mechanism that results in assortative mating between corn and rice host strains. Clearly other pre- or perhaps even post-mating mechanisms are important for the maintenance of host strains in S. frugiperda.