In wheat, Illinois producers are mostly concerned about stripe rust, but other diseases including stem and leaf rust can occasionally cause issues. In corn, the major issue is Southern rust. Soybean rust also should be on the radar, despite it not developing into the widespread issue once predicted. Other diseases are resident/established, meaning they overwinter in our region and we see them at some level annually. These include diseases such as grey leaf spot, tar spot and northern leaf blight in corn, and frogeye leaf spot in soybeans. Tracking these diseases during the season is less useful for management, but may help producers know where more inoculum may be present the following year, resulting in potentially higher disease risk. Illinois Extension will be monitoring the rusts this season in wheat, corn and soybean and monitoring counties where tar spot has not been previously identified. It is more important to track the yearly spread of tar spot into new areas as opposed to monitoring areas where it has been found. Remember, once it is found, it is established in that area from that point forward. Not finding tar spot in a county where it was detected in the past does not mean the disease was absent, but more likely means the number of sites or samples were not sufficient to detect it, and that relative levels were low. That being said, Extension researchers are focusing on areas where this disease has yet to be detected. Starting in May, if the county already has had tar spot reported in the past, it will be shaded in on the map. Source - http://www.kmaland.com