Esneider Mahecha, Dalitso Yabwalo, Connie Tande, Shaukat Ali, Madalyn Shires, and Emmanuel Byamukama South Dakota State University, Department of Agronomy, Horticulture and Plant Science, Brookings, SD, USA Corresponding Author: Shaukat Ali, shaukat.ali@sdstate.edu Abstract Fusarium head blight (FHB), caused by Fusarium graminearum (Fg), is one of the most important diseases of wheat. FHB results in grain yield loss, seed quality reduction, and the accumulation of mycotoxins such as deoxynivalenol (DON). FHB disease management is mainly with the use of partially resistant cultivars and the application of synthetic fungicides to guarantee a higher yield. However, the constant application of synthetic fungicides causes negative impacts on humans and the environment. Additionally, fungicides used to control Fg belong mainly to one class of fungicides, the triazoles, increasing the risk of loss of pathogen sensitivity. Therefore, there is a need to test and implement new eco-friendly alternatives for managing FHB. Essential oils (EOs) are volatile secondary metabolites extracted from plants, composed of a mix of bioactive compounds with known antifungal properties. In this study, we evaluate the efficacy of two pure EOs (tea tree and lemongrass), two commercial EOs (Thymox® and Timorex®), and two bioactive compounds present in EOs (carvacrol and thymol) in the management of FHB. The study was conducted in vitro using inhibitory disk diffusion to detect the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC). Additionally, conidia germination inhibition was evaluated, and volatile activity was reported. The EOs and constituents were tested under greenhouse and field conditions. FHB Disease index (DI), yield, Fusarium damaged-kernels (FDK), and DON were evaluated. There was 100% MIC in Fg with lemongrass at 1000 ppm, Thymox at 500 ppm, and carvacrol, and thymol at 200 and 500 ppm, respectively. One hundred percent spore germination inhibition was observed at 1000 ppm of lemongrass, tea tree, and Thymox, and at 500 ppm of carvacrol and thymol. All the EOs concentrations showed a MFC equal to the MIC except for carvacrol, where fungal regrowth was observed at 500 ppm. Volatility fungistatic activity was observed in lemongrass, Thymox, and thymol with 6.25 to 38.44% of mycelial growth inhibition compared with the untreated. For the greenhouse and field studies, Plants treated with lemongrass, carvacrol thymol, and Thymox showed a significantly lower DI (P<0.05) relative to the untreated. In the field trial, the EOs showed a DI reduction of 40% and a decrease of DON concentration between 36 and 59% for all the treatments with EOs compared to the untreated. In vitro and in vivo experiments, we reported the fungicidal and fungistatic potential of the EOs lemongrass, carvacrol, thymol, and Thymox in the control of Fg.