Pastoral grasses and legumes as potential host plants for fall armyworm Spodoptera frugiperda (J.E. Smith) development.

Abstract The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is a highly polyphagous, migratory pest native to the tropical and subtropical region of Americas. Grass crops particularly corn have been most heavily impacted since S. frugiperda invaded Australia in 2020. In northern Western Australia, S. frugiperda is primarily a problem in dry season (May to October) crops when there are abundant host plants available in monocultures. During the wet season (November to April) it is not known what host plants may support larval growth and development. Accordingly, this present study undertook a no-choice feeding bioassay to assess larval and pupal development on several grasses and legumes that are present over the wet season in northern Western Australia to evaluate their potential as suitable host plants for S. frugiperda . Maize (control) and sorghum were the most suitable hosts for S. frugiperda development as they supported greater larval and pupal survival, heavier larvae and pupae, and shorter development period. Following maize and sorghum, pastoral grasses, particularly blue grass, and a weedy grass, barnyard grass, had comparable effects on larval and pupal development. Legume pastures (Cavalcade, butterfly pea, and siratro) were unsuitable hosts in this bioassay as very few larvae completed their development to adults. This study demonstrates the potential for rangeland pasture grasses and weedy grasses as wet season host plants for S. frugiperda . They provide the necessary green bridge for S. frugiperda populations to survive. It is recommended that pastoralists monitor their grass forage for S. frugiperda and consider management if significant reductions in biomass are detected.