Nearly all soybean fields in the area are reaching R7 and beyond, where leaves are yellowing and dropping to the ground. While some fields are progressing normally, a large number may have areas that appear to be maturing at a much faster pace. These areas may, in fact, be infected with the Cercospora kikuchii pathogen. Cercospora Leaf Blight is appearing at a very high level this year in the state, as the abundance of rain and heavy morning dew and fog we have been seeing make the presence of the disease more likely.
The blight usually appears first in the upper leaves of the soybean canopy. A bronzing of the leaves occurs, which appears like the natural soybean maturation process. Premature defoliation can of course be detrimental if it occurs prior to seed-fill. The fungus can also cause other problems in soybean. One of those is purple seed stain, which doesn't adversely affect yield, but may cause issues at the market.