Figure 3. Crop Risk Tool for Purdue Ag Centers in Indiana on June 26, 2025 (https://connect.doit.wisc.edu/cpn-risk-tool/). These disease risk models are only valid when the crop is present and in a vulnerable growth stage. Risk may be mitigated in commercial production by application of a protective fungicide. Corn diseases include tar spot and gray leaf spot. Risk is based on probability of spore presence. Corn is vulnerable to these diseases when in the growth stages V10-R3.
Across Indiana the risk of favorable environmental conditions for tar spot is much less (green vs red) than it was early in the week. The hot weather we have experienced is helping reduce the risk.