Gangrene of seedlings – It manifests itself in the darkening and narrowing of the seedling stems, and then turning over and dying off plants. This disease spreads to neighboring plants and forms outbreaks – blanks with remnants of dead plants. Seedling blight is common in seedling growing indoors. High humidity favors the development of the disease, insufficient light and too high a density of seedlings. Only decontaminated soil must be used, remove diseased seedlings and ventilate the room.