Initial infections with Septoria tritici blotch (caused by Mycosphaerella graminicola) tend to be on the lower leaves, progressing to the upper leaves and spikes if environmental conditions remain favorable.

Cool temperatures (10-15°C) and prolonged wet, cloudy weather favors the development of these diseases. This is primarily a disease of wheat, but other cereals are somewhat susceptible. The disease is limited to temperate wheat-growing areas where cool and moist conditions prevail.