Spores of powdery mildew fungus on a barley leaf. This parasitic fungus spreads over the leaf surface and in through the stomates, extracting nutrients from the barley plant. It then forms these upright chains of spores that readily spread the infection. Powdery mildew infection can severely reduce crop yields and economic productivity.

Imaged using scanning electron microscopy by Prof. Roger Wepf, University of Queensland.

Size: the terminal spores are about 20 micrometres long.