Oviposition preferences, Bt susceptibilities, and tissue feeding of fall armyworm (Lepidoptera: Noctuidae) host strains.
BACKGROUND: The fall armyworm, Spodoptera frugiperda (Smith), is a pest of many economically essential crops across several continents. Documentation of resistance to Bt toxins has caused growing concern in agricultural communities regarding the ability to keep fall armyworm populations below economic thresholds. The existence of two host strains referred to as the 'rice' and 'corn' strains is a complicating and under-researched factor of fall armyworm biology and management. It is essential to characterize the differences between the host strains, as well as their rice/corn hybrid offspring, to elucidate their contributions to field-evolved resistance. RESULTS: Corn was a preferred oviposition host for both rice and corn strain fall armyworm, and a suitable larval host plant for each of the four populations tested. Corn strain females displayed a significant preference towards oviposition on plants that lacked mechanical damage. The rice strain population was generally less tolerant to Cry1F corn tissue than the corn strain and hybrid populations, which performed in a similar way to one another. CONCLUSION: The preference for corn as an ovipositional host may have an impact on resistance management when coupled with differential host strain Bt tolerances, though more studies are needed. Hybrid tolerance to Bt toxins could possibly contribute to the evolution of Bt resistance. This is the first study to compare the larval fitness and survival of rice/corn hybrid fall armyworm to that of pure host strains using a tissue-based approach.