The P. chartarum fungus grows in the humid, protected dead material at the base of forage plants. Fungal growth is favored by warm, wet, humid weather, or with heavy dews or irrigation. Spore levels can rise rapidly under these conditions. The practice of intensive grazing increases the risk of facial eczema, because animals in closely-grazed pastures consume vegetative matter that may be heavily contaminated with fungus spores. Facial eczema is relatively common in areas of New Zealand.
Perennial ryegrass is the grass species most associated with facial eczema.
P. chartarum does not grow well in legumes. Under normal conditions, the chlorophyll in ingested forage plants is metabolized by rumen microbes into phylloerythrin, which is absorbed and transported to the liver. Healthy livers then transfer the phylloerythrin to the bile for excretion. Livers damaged by the sporidesmin toxin cannot properly metabolize phylloerythrin, which then accumulates in peripheral blood. Growth and milk production are dramatically reduced.