disease of pear trees close-up. damage fruit tree. sick leaf of fungal infection gymnosporangium sabinae. rust spot on

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