LB 5-44 - Soil-mediated associational resistance to fall armyworm, Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) due to push-pull cropping soil legacies

Cropping systems and soil legacies are intrinsically linked and can influence direct and indirect plant defense mechanisms against phytophagous insects in agroecosystems. In this study, we tested how soil conditioned by maize (Zea mays L.) (Poales: Poaceae)- Desmodium sp. (Fabales: Fabaceae)-Brachiaria sp. (Poales: Poaceae) companion cropping systems (push-pull) and maize monoculture (non-push-pull) alters maize phytochemistry and subsequent resistance to an invasive herbivore, fall armyworm (Spodoptera frugiperda Smith) (Lepidoptera: Noctuidae). Maize was grown in soils collected from push-pull and monoculture smallholder farmer fields in Kwale, Homabay and Kisii counties, Kenya. We compared maize growth, larval feeding by S. frugiperda, production of volatile and non-volatile defense secondary metabolites, and behavioral response of the egg-larval parasitoid Chelonus bifoveolatus Szpligeti (Hymenoptera: Braconidae) on maize volatiles from maize grown in soils conditioned by push-pull and non-push-pull cropping systems. Maize plants grown in soil from push-pull cropping systems had a higher growth rate compared to those grown in monoculture soil. Spodoptera frugiperda neonates consumed more leaf tissue on maize plants grown in monoculture conditioned soil than those grown in push-pull conditioned soil. Maize plants grown in soil from push-pull fields constitutively emitted higher and qualitatively different volatile and non-volatile secondary defense metabolites compared to those grown in soil from maize monocultures. Female C. bifoveolatus were more attracted to volatiles from maize plants grown in push-pull conditioned soils than those grown in non-push-pull soils. Our results indicate that conditioning soil by push-pull cropping system enhances maize growth and alters phytochemistry, resulting in increased resistance to Spodoptera frugiperda and increased attraction of C. bifoveolatus.