Sorghum and maize flavonoids are detrimental to growth and survival of fall armyworm Spodoptera frugiperda

Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) is becoming an invasive pest globally, and it causes significant yield losses in sorghum ( Sorghum bicolor (L.) Moench) and maize ( Zea mays L.). In this study, we demonstrated that sorghum and maize flavonoids affect survival of FAW larvae. Larvae reared on an artificial diet supplemented with sorghum flavonoids showed significant mortality and decreased body weight. When sprayed on leaves of susceptible maize lines, flavonoid extract effectively reduced the growth and increased the mortality of FAW larvae. As FAW is a major pest of maize, we further investigated the larval mortality when reared on maize lines overproducing flavonoids compared to their near-isogenic wild-type lines. The detached leaf assays showed significantly high mortality of larvae that were fed on flavonoid producer lines compared to wild type. The peritrophic membrane that protects the midgut was severely damaged in larvae fed on leaves of flavonoid producer lines compared to wild type. The effectiveness of the flavonoids as feeding deterrents by endogenous expression and exogenous application demonstrates the eco-friendly potential for the management of FAW larvae.