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 green fall parasite treatment foliage prevention farming unhealthy orange pathology infected environment gardening yellow plant agriculture fungi pest pathogen fungus