In vitro antifungal tests with one of the most popular medical substance in the world – L – ascorbic acid, widely known as vitamin C, were conducted with three of the most spread plant pathogens in Bulgaria: Monilia frucigena, Alternaria solani and Venturia inaequalis in order to evaluate the direct antifungal action of the acid used in agriculture as ISR promoter (phytovaccine). The expression of pesticide action of ISR promoters is not unusual unlike the vaccines for the animals and humans. Conducted tests shows the strong antifungal activity of L – ascorbic acid towards mycelium and conidiospores of Alternaria solani and Venturia inaequalis and a very weak antifungal action towards Monilia frucigena which means that vitamin C can be used as a direct fungicide agent and phytovaccine in the pest management simultaneously. The substance has excellent water solubility which make is very appropriate for formulation as a plant protection product.
Keywords: L-ascorbic acid, antifungal, ISR promoter, Monilia frucigena, Alternaria solani, Venturia inaequalis