The purpose of that article was to show the significance of water as the source of plant pathogens, and need of it effective disinfection methods in modern agriculture and horticulture. The increase in the cost of agricultural water use for crop irrigation and the necessity of using the same water several times, as well as the changing climatic conditions, including prolonged shortage of atmospheric precipitation and often extreme temperatures during the summer, necessitate the selection of an effective, easy to apply and economical method of disinfecting recirculated water to eliminate or minimize the occurrence of the most serious plant pathogens inhabiting various water sources. Among them, microorganisms of the genera Phytophthora, Pythium and Fusarium, and the species Rhizoctonia solani, Verticillium dahliae and some pathogenic bacteria pose the most serious threat. Some of them can be found in rivers, streams, ponds and water reservoirs, others are soil-borne pathogens that cause root and stem base rot of many plant species. The available literature describes at least a dozen methods of water disinfection, among them slow filtration through sand or lava filters, chlorination and heating. The literature data indicates that the use of sand filters is the most effective, safe and cheapest method of water disinfection.