Powdery mildews are one of the world’s most frequently encountered pathogenic fungi causing quantitative, and qualitative yield losses in all kinds of  annual, and perennial crops, horticultural , and ornamental crops, cash crops, industrial crops, forest trees, shrubs, grasses, and all kinds of vegetation in tropical, sub-tropical, and temperate regions of the world. On cruciferous crops, it is the fourth most wide spread, and devastating disease causing yield losses up to 90 per cent with loss in oil quality, quantity up to 7 per cent in rapeseed-mustard.  Powdery mildews are often very conspicuous owing to their profuse production of conidia on the host surface in the form of white granular coating giving them their common name. Powdery mildews are also favourable host-pathosystem as model for basic research on host–parasite interactions, developmental morphology, cytology, and molecular biology to dissect effector proteins/ genes governing different biological functions. This book entitled” Powdery mildew Disease of Crucifers: Biology, Ecology and Disease Management” is the comprehensive treatise on fourth most important disease of crucifers encompassing all the published information  for the use of researchers, teachers, students, extension experts, industrialists and farmers. The information has been arranged in 11 chapters with appropriate headings and subheadings, illustrations, photographs, graphs, figures, tables, histogram, coloured plates of micrographs, electron micrographs, and flow charts for effective and stimulating comprehension by the readers. The different chapters of the book include detailed information on status of disease, and pathogen; the disease, its distribution, symptomatology, host range, yield losses, and disease assessment; pathogen, its taxonomy, morphology, phylogeny, variability, sporulation, survival, and perpetuation; spore germination, infection, pathogenesis,  disease cycle, epidemiology, forecasting, and fine structures; mechanisms of host resistance, biochemical, histological, genetical, molecular including cloning, and mapping of R genes; sources of resistance, disease resistance breeding strategies, and genetics of host-parasite interactions; disease management through cultural, chemical, biological, host resistance, and integrated approach; standardized reproducible techniques have also been included. Although, we have taken every care to seek permission from the authors/publishers to include their valuable contributions in this book but never the less inadvertently for any error, we humbly request to excuse us. All sources have been duly acknowledged. For any error, omission, we shall feel obliged to get your suggestions to include in the revised editions.