Seed treatment of dent and sweet corn with alginate nanoemulsions of lemongrass essential oil against Fusarium graminearum and Pythium sylvaticum

Seed treatments are widely used to protect seeds from pathogens during germination and early seedling development. Although essential oil-based nanoemulsions have been investigated under in vitro conditions, their performance as seed treatments and their effects on seed physiological potential and health under soil conditions remain underexplored. This study evaluated alginate-based nanoemulsions containing lemongrass ( Cymbopogon flexuosus ) essential oil at concentrations of 5%, 10%, 20% (v/v), as well as pure essential oil, using in vitro assays and in vivo soil assays against Fusarium graminearum and Pythium sylvaticum . Nanoemulsions were successfully produced, with droplet sizes of 111–128 nm and polydispersity indices ranging from 0.20 to 0.32, remaining stable for up to 90 days. In vitro assays demonstrated significant inhibition of both pathogens, with inhibition levels reaching 59.5% for F. graminearum and 61.3% for P. sylvaticum when nanoemulsions containing 20% essential oil were applied, while pure essential oil resulted in higher inhibition. Seed treatments with lemongrass nanoemulsions preserved germination and cold test performance in dent corn and sweet corn, whereas pure essential oil severely reduced seed viability. Under soil conditions, nanoemulsion treatments did not significantly reduce disease severity or consistently improve seedling growth parameters (root/shoot length, wet/dry weight) compared with inoculated controls for either pathogen. These results indicate that lemongrass essential oil nanoemulsions are compatible with seed quality and demonstrate antifungal and antioomycete activity in vitro, but their effectiveness under the soil conditions evaluated was limited. Further studies are needed to elucidate how formulation dynamics and the availability of active compounds at the seed-soil interface affect their efficacy under soil conditions.