Today Lebanese viticulture ranks eighth in the agricultural sector where powdery and downy mildew are the most economically significant diseases of grape varieties. In fact, due to the lack of technical know-how in controlling these diseases under organic regulation, winegrowers use a wide range of phytosanitary products regardless their ecological cost in order to reduce any loss of harvest. Therefore, the objective of this work was to assess the efficacy of using micronized sulfur, copper hydroxide, potassium bicarbonate, Bacillus pumilus and Bacillus amylolequeficiens in preventing and controlling powdery and downy mildew infection with the usual behavior of the farmers. The experiment was conducted in the season 2021, in two vineyards located in the Bekaa Valley planted with varieties susceptible to powdery mildew namely Chardonnay and Tempranillo. Three different treatment programs from
leaf development until the harvest were evaluated for their effectiveness against powdery and downy mildew. Among these three treatments, two were compared to the standard farmer program. All the three spray programs did not show any incidence on the severity of powdery and downy mildew on the leaves or on the grapes. To be precise, the 2021 vintage was a year with very low mildew pressure given the weather conditions unfavorable to the development of the fungus.