Heart rot and root rot of pineapples is caused by several species of the plant-pathogenic water molds Pythium and Phytophthora. These soil-borne organisms cause severe diseases of many crops worldwide, including pineapple. Heart rot affects the basal leaf tissues and can rot fruit as well, while root rot causes root necrosis that, if left unaddressed, may lead to reduced crop yields and total crop failure. The infection process and intensity of these diseases depend on variables such as topography, drainage, rainfall, and soil pH. Pineapple heart and root rots are most severe in high-rainfall areas and irrigated soils with poor soil drainage. Root rots may increase in severity after nematode infections of roots.