Influence of Host Plant on the Susceptibility of the Fall Armyworm to Insecticides1

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Abstract
Larvae of Spodoptera frugiperda (J. E. Smith) from a laboratory culture (originally collected from rice near Hammond, La.) reared on bermudagrass, corn, millet, and soybean were treated topically with carbaryl, methyl parathion, permethrin, and trichlorfon to establish log dose-probit lines for each insecticide on each host. Differences among hosts were not detected ( P < 0.05) in the toxicological response of larvae treated with methyl parathion. Larvae reared on millet were 6X more susceptible ( P < 0.05) to trichlorfon than larvae reared on the other 4 hosts. Larvae reared on bermudagrass and millet were more susceptible ( P < 0.05) to carbaryl and permethrin than larvae reared on corn, cotton, or soybean. Cultures collected from corn and signalgrass, previously treated with carbaryl, near Hammond in 1979 exhibited resistance to carbaryl (41X), methyl parathion (113X), permethrin (17X), and trichlorfon (31X) in comparison to the laboratory culture.