disease of pear trees in autumn. damage fruit tree. sick leaf of fungal infection gymnosporangium sabinae. rust spot on

rust pear gymnosporangium damage spot disease leaves fungal sick fruit autumn leaf tree nature sabinae phytopathology aeciospores closeup fungicide grow danger infestation rusty diseased summer plant environment green unhealthy orange fungi parasite foliage pathology agriculture fungus pest farming infected gardening treatment fall yellow pathogen prevention