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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Insect Behavior and Biocontrol Research » Research » Publications at this Location » Publication #141030

Title: Identifying host strains of fall armyworm (Lepidoptera: Noctuidae)in Florida using mitochondrial markers

Author
item Meagher, Robert - Rob
item GALLO-MEAGHER, M. - UNIV OF FL, GAINESVILLE

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2003
Publication Date: 12/1/2003
Citation: Meagher Jr, R.L., Gallo-Meagher, M. 2003. Identifying host strains of fall armyworm (Lepidoptera: Noctuidae)in Florida using mitochondrial markers. Florida Entomologist. 86(4):450-455.

Interpretive Summary: The fall armyworm is a moth pest whose larvae attack various agricultural crops such as corn, forage grasses, turf, peanuts, cotton, and rice in the eastern and central United States. These moths are present all year in southern Florida and Texas, but they migrate northward during spring. Growers of sweet corn in southern Florida may apply over 20 insecticide applications per season to control this pest. Because of environmental concerns over insecticide applications, new population monitoring techniques and alternative control strategies are needed. Previous research has shown that the species fall armyworm is actually composed of two morphologically identical host strains. One strain prefers to feed and develop on corn and other large grasses, while the other strain prefers smaller grasses such as rice and bermudagrass. It is important to know the difference between these strains because they differ in their feeding on resistant plants and on their susceptibility to insecticides. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, improved a molecular technique that identifies the two host strains. This report describes the use of this improved technique to identify moths in Florida. Sex pheromone-baited traps were placed in different locations in north and central Florida and the host strain of the attracted males was identified. Our research showed that males held in traps for at least 15 days could still be analyzed. Rice strain moths were common in habitats with large areas of small grasses, corn strain moths were common in large areas planted to corn, and habitats with mixed large- and small-grass plantings contained both strains. Our techniques will provide a valuable sampling system to determine the population ecology habits of fall armyworm populations in numerous habitats, including overwintering areas of southern Florida.

Technical Abstract: Two molecular techniques were used to identify host strains of fall armyworm, Spodoptera frugiperda (J. E. Smith) from male moths captured in pheromone-baited traps in north-central and central Florida. Moths collected in 1998 were analyzed using direct detection of mitochondrial DNA (mtDNA) RFLPs generated from restriction endonuclease digestion of total DNA, while moths collected in 2000 and 2001 were analyzed using a mitochondrial cytochrome oxidase subunit I (COI) gene PCR-RFLP marker. Both techniques could distinguish between rice and corn strain moths, however, the COI PCR-RFLP marker was more robust as indicated by a time interval experiment that showed that moths held for up to 15 days in a "bucket trap" could still be used for strain diagnosis. In a field study, our strategy gave results consistent with expectations. Rice strain moths were common in habitats with large areas of small grasses, corn strain moths were common in large areas planted to corn, and habitats with mixed large- and small-grass plantings contained both strains. Our methodology of combining pheromone traps with PCR-RFLP analysis will provide a valuable sampling system to determine the population ecology habits and strain isolating mechanisms of fall armyworm populations in numerous habitats, including overwintering areas of southern Florida.