Efficacy of Essential Oils and Compounds in Controlling Sunflower Pathogens: In vitro Evidence Against Sclerotinia sclerotiorum and Diaporthe gulyae

Presenting Author: Esneider Mahecha, Student Intern, South Dakota State University, Brookings, SD, USA
Authors:
Madalyn Shires, Assistant Professor and Extension Plant Pathology Specialist, South Dakota State University, Brookings, SD, USA
Connie Tande, Senior Microbiologist, South Dakota State University, Brookings, SD, USA
Emmanuel Byamukama, Assistant Professor, South Dakota State University, Brookings, SD, USA
Dalitso Yabwalo, Post Doc Research Associate, South Dakota State University, Brookings, SD, USA

Sunflower is an important commercial crop that serves as a significant source of food for human consumption, However, the crop is vulnerable to several diseases, including Sclerotinia head rot caused by Sclerotinia sclerotiorum (S.S) and phomopsis stem canker caused by multiple species of Diaporthe, among them Diaporthe. gulyae (DG). Management of these diseases often involves using resistant hybrids and fungicide applications. However, the excessive use of fungicides can lead to pathogen resistance and environmental and health concerns. Biopesticides, such as essential oils (EOs) and their components, are promising alternatives for controlling fungal diseases. This study evaluated the effectiveness of four essential oils: tea tree, lemongrass, neem, and karanja, and three components: carvacrol, thymol, and linalool. In vitro the minimal fungicide concentration (MIC) and minimal fungicidal concentration (MFC) were determined. Additionally, sclerotium germination of SS and volatility activity assessed.
Lemongrass exhibited the MIC at 500 and 1000 ppm in SS and DG, respectively. Carvacrol and thymol showed the MIC at 200 ppm for both pathogens. The MFC was the same as the MIC for lemongrass and thymol, while carvacrol exhibited regrowth at 200 ppm. Volatile activity inhibition was observed at 700 ppm for carvacrol and thymol in DG. The sclerotia germination test showed complete inhibition for Lemongrass, carvacrol, and thymol at 1000 and 500 ppm. this study in vitro suggests the potential of lemongrass, carvacrol, and thymol as natural fungicides for controlling SS and DG."