Now is the time to start thinking about controlling leaf diseases in wheat if necessary. Conditions have been wet enough in the southern Iowa wheat-producing areas to promote significant leaf disease development. Wheat can be affected by a number of foliar diseases caused by fungi, including Septoria leaf blotch, powdery mildew, and tan spot. There are also three different rust fungi that can infect wheat. Leaf rust, Puccinia recondita, is the most common rust disease and has the most destructive potential of the foliar diseases.