powdery mildew caused by podosphaera aphanis on green cucumber leaf

affected agriculture aphanis biology broadleaf cichoracearum closeup communis cucumber danger detail disease diseased erysiphe foliar fungal fungi fungual fungus gardening green grow infection leaf microorganism mildew mold parasite pathogen pathology pesticide phytopathology plant plantaginis podosphaera powdery problem protection repellent soil sphaerotheca spores spot symptoms vegetable white