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Submitted to: Journal of Insect Behavior
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/24/2011 Publication Date: 1/9/2011 Citation: Meagher Jr, R.L., Nagoshi, R.N., Stuhl, C.J. 2011. Oviposition choice of two fall armyworm (Lepidoptera: Noctuidae) host strains. Journal of Insect Behavior. 24:337-347. Interpretive Summary: The fall armyworm is a moth pest whose larvae attack various agricultural crops such as corn, forage grasses, turf, peanuts, and cotton in the southeastern, 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 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 learn some of the biological and behavioral differences 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, conducted laboratory experiments to determine if corn strain and rice strain females laid their eggs in the same locations. Corn strain females equally placed eggs on corn and grass plants but rice strain females placed more eggs on grass plants compared to corn. These results will help scientists develop improved monitoring and management methods for this agricultural pest. Technical Abstract: Fall armyworm, Spodoptera frugiperda (J. E. Smith), is a noctuid species that is composed of two morphologically identical sympatric host strains (corn and rice) that differ in their distribution among plant hosts. In an effort to explain observations of host fidelity in the field, ovipositional preference of the two strains on corn (Zea mays L.) or pasture grass (Cynodon nlemfuensis Vanderyst var. nlemfuensis) was determined using two greenhouse bioassays. In the first bioassay, corn strain females placed more eggmasses on the screen enclosure than on corn plants while grass plants contained an intermediate number of eggmasses. Rice strain females placed most of their eggmasses on grass plants. In the second bioassay, corn strain females placed an equal number of eggmasses on corn and grass plants in comparison to rice strain females which placed >3.5x more eggmasses on grass plants than on corn plants. Individual eggs as part of the eggmasses were also counted on plants and on the screen enclosure. Corn strain females equally placed eggs on the two host plants and on the screen enclosures, however rice strain females placed more eggs on grass plants compared to corn plants or the screen enclosure. This is the first report of consistent differential oviposition between corn and rice strain fall armyworm females. |
