うどんこ病
Powdery mildew can be found in all wheat growing areas of the United States but usually will be most severe in the east and southeast. It is more common in areas with a humid or semi-arid environment where wheat is grown. Powdery mildew has become a more important disease in some areas because of increased application of nitrogen fertilizer, which favors the development of the fungus. Severe symptoms of powdery mildew can cause stunting of wheat. If unmanaged, this disease can reduce yields significantly by reducing photosynthetic areas and causes non-seed producing tillers. Powdery mildew causes reduced kernel size and lower yields. The sooner powdery mildew begins to develop and how high on the plant it develops by flowering the larger the yield loss. Yield Losses up to 45 percent have been shown in Ohio on susceptible varieties when plants are infected early and weather favors disease.