Which one is soybean rust?
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Answers below!

Symptoms of soybean rust include spots or lesions that increase in size over time and change color from gray, to tan, reddish-brown or black. These symptoms are not exclusive to rust! Other diseases of soybean including brown spot, bacterial blight, and particularly downy mildew can easily be confused with soybean rust.

It is absolutely necessary to observe sporulation in order to diagnose rust.
Read more about how to scout for and identify soybean rust»