MSU Extension field crop pathologist Dr. Martin Chilvers addresses tar spot in corn - a new crop disease in Michigan in the past few years.  Tar spot of corn is a new disease to the United States. Caused by the fungus Phyllachora maydis, the disease has the potential to cause significant yield loss. Tar spot was first found in Indiana and Illinois in 2015 and confirmed in Michigan in 2016. In 2018, tar spot was observed in 27 counties across Michigan and caused losses of more than 50 bushels per acre in some fields. A new extension resource was published recently on the Crop Protection Network—look for “CPN-2012 Corn – Tar Spot” under the library tab.