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Downy Mildew

Source: Gary Bergstrom, Cornell University
Source: Ken Wise, Cornell University
Downy Mildew  soybean disease locations by NY county
Click map to enlarge

Peronospora manshurica
Downy mildew is very common and widespread throughout NY, and can often be found in most soybean production fields each year.  Symptoms include pale green to bright yellow spots appearing first, which will eventually become necrotic spots.  During humid conditions, sporulation may be observed at these spots on the lower leaf surface.  It is not typically considered a disease of economic importance in NY, and therefore usually requires no management recommendations.   Also, keep in mind that most foliar fungicides available for soybeans are not labeled for downy mildew and would have very limited effect, if any, because the pathogen that causes downy mildew is an oomycete and is not in the same category as our other foliar fungal diseases. 


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