うどんこ病
Powdery mildew on sugarbeets can be found wherever the crop is grown in the U.S. It infects plants in the spring when the weather begins to get warm again. The spores land on the leaves and rapidly grow, forming a white mildew film on the foliage within a week of infection. This mildew penetrates the cell wall and begins to absorb nutrients from the leaves. This eventually turns the leaves yellow and kills them. If it proceeds uncontrolled the infection will spread through an entire field within a month. Tests have shown that when left untreated powdery mildew can reduce yields by 27%. Control is best achieved through the use of sulfur, which has been found to increase yields by 38%.