Submitted to: Ecological Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 18, 2004
Publication Date: October 1, 2004
Citation: Meagher Jr, R.L., Nagoshi, R.N. 2004. Population dynamics and occurrence of Spodoptera frugiperda host strains in southern Florida. Ecological Entomology. 29(5):614-620.. 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, 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. 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, used sex pheromone-baited traps to collect specimens from southern Florida. Rice strain moths were common and were found in all habitats that were sampled. Corn strain moths were collected mostly during spring in areas of sweet corn production. Our results suggest that the corn strain population is much more limited in its geographical range, which may provide opportunities for controlling this subpopulation.
Technical Abstract: The development of an area-wide management program for the migratory pest fall armyworm [Spodoptera frugiperda (J. E. Smith)] requires knowledge of its preferred habitats throughout the year and a detailed description of seasonal changes in population numbers. Molecular markers were used to determine the host strain ('corn' or 'rice') of male moths captured in sex pheromone-baited traps placed in different habitats in the overwintering areas of southern Florida. Our results indicated that rice strain moths were found in all traps and was the primary population observed in pastures, turf, and wetlands throughout southern Florida. One trap adjacent to an agricultural site and two traps within an urban environment collected a higher percentage of corn strain moths, although most were captured in the spring-growing season. These results represent the first geographical survey of fall armyworm host strain distribution and indicate that corn strain moths are limited in their habitat choice while rice strain moths have a substantially broader range. The localization of the corn strain population to discrete areas at specific times of the year provides an opportunity to reduce or delay its northward migration.