The 2018 Wisconsin corn growing season was a challenging one when it comes to diseases. There were substantial disease epidemics across the entire corn belt of Wisconsin in 2018, with some fields hit by multiple diseases. Gray leaf spot started earlier than normal in the southwest portion of the corn growing region of Wisconsin. The emerging disease, tar spot, then moved in. Tar spot started in the south and southwest but moved north and east leaving many corn fields to dry down abnormally quick. Northern corn leaf blight also caused some issues in the central and northern corn production areas of the state. Then ear rots started to show up near harvest, with mycotoxin levels, like vomitoxin, being a significant issue in corn silage and some grain fields. To add insult to injury a new bacterial disease of corn was also reported for the first time in Wisconsin. Bacterial leaf streak, caused by a Xanthomonas sp., showed up in one field in Pierce Co., Wisconsin. Admittedly, the tar spot epidemic was probably the most impactful, followed by issues with ear rot and vomitoxin contamination.
Soil Science Extension
University of Wisconsin Madison