Septoria leaf blotch infection. Coloured scanning electron micrograph (SEM) of Septoria tritici (also known as Mycosphaerella graminicola) fungus (grey) infecting a wheat (Triticum sp.) leaf. Infection causes brown lesions and cell death. This reduces the area of green leaf for photosynthesis and so results in significant yield losses. Magnification: x240 when printed at 10 centimetres wide.