european wild pear tree with sick leaf of fungal infection gymnosporangium sabinae. pyrus pyraster. branches with pear

wild pyraster european tree pyrus pear ovate margin rust gymnosporangium damage spot disease fungal sick fruit autumn leaf nature sabinae phytopathology aeciospores fungicide danger infestation rusty diseased fungi parasite green agriculture environment fall pathology gardening farming treatment prevention fungus pest pathogen infected astringent ripening thorny rosaceae thorn