Fair-weather fungus

Photo competition: 2nd place in the category ‘Pathogen’

Brown spots, dried leaves and a white coating reminiscent of mould – this plant looks sick. This is due to an infection with powdery mildew, a widespread fungal disease of crop and decorative plants. Powdery mildew (Erysiphaceae family) is also known as fair-weather fungus, as it develops in warm and dry conditions. Fittingly, the photo was taken at the end of July during a morning walk by the photographer. The mealy-white and, in advanced cases, dirty-brownish coating on the upper side of the leaves as well as deformed shoot tips and leaves are typical symptoms of the fungus. Plants infected with mildew fail to photosynthesise, stagnate in growth and die if not adequately treated.