EN
Investigations were aimed at the possibility of conventional fungicides limitation in cucumber protection against powdery mildew by sorting and introducing the most effective natural products. There were examined products with different biologically active substances: biostimulators, fertilisers and products containing silicon. The effectiveness of tested products against E. cichoracearum were evaluated with macroscopic methods (evaluation of dynamic of powdery mildew development) and microscopic methods (analyses of micromorphology of leaf epidermal surface). There were selected products characterized by the highest efficiency in the fight against E. cichoracearum. The best results were obtained after the application of products based on grapefruit extracts, tea tree extract (Melaleuca alternifolia) and orange oil. The effects of the use of products were characterized by E. cichoracearum spores and mycelia destruction. After spraying in-fected cucumber plants the distortion of hyphae and conidiospores of powdery mildew were visible.