Determination of anti-mildew activity of essential oils against downy mildew of sunflower caused by Plasmopara halstedii

Abstract

To evaluate the anti-mildew activity of the commercial essential oils (EOs) against pathotypes ‘771’ and ‘773’ of P. halstedii in mineral salt medium, the EOs obtained from different parts of Greek sage, black cumin, bay, mustard, St. John’s wort, French lavender, garlic, grape, and ginger plants were examined at concentrations of 0.2%, 0.4%, 0.6%, 0.8%, and 1% on leaf discs of susceptible sunflower variety ‘08-TR-003’. The ginger EO had the highest anti-mildew activity at a concentration of 1% and was found to be the most effective with a decrease in sporangium quantity above 90% for pathotypes ‘771’ and ‘773’. The EOs of garlic, St. John’s wort, and grape followed it, respectively, with a decrease in sporangium quantity above 80%.