うどんこ病
Powdery mildew affects more the 7600 species of hosts worldwide, including subsistence crops Although rose powdery mildew will most directly affect the rose connoisseur, it is part of this larger family of powdery mildews, which can affect the crops used for food and survival in many countries, thereby having economic and human impacts beyond that of an unsightly rose bush. Research shows that total yield loss from powdery mildew on cereal crops alone can vary anywhere between 2 and 30% depending on the host and the environmental conditions. Additionally, the wholesale value of roses annually exceeds $100 million in the United States, so the national economic impact from the flower industry cannot be ignored As explained by an old gardener's adage 'Weeping Mildred! She's no friend of the gardener and certainly no friend of me'.