The preventative and curative effects of some plant derived agents based on plant extracts or essential oils were studied at different concentrations against _Erysiphe cichoracearum _DC. ex Merat, the causal pathogen of okra powdery mildew by the detached leaf-disk and potted plants bioassays. Through detached leaf-disk assay, the highest mean preventative effect (97.74%) was recorded by neem seed oil followed ... إقراء المزيد