Time to Scout for Diseases in Field Crops: What to Look for in Corn

August 1, 2022

Darcy Telenko, Assist Prof of Botany & Plant Pathology, Botany & Plant Pathology, Purdue University

Yes, we have found active tar spot in Indiana. 

Corn growth stages are quite variable across Indiana but a number of areas have moved into tasseling or beyond. Therefore, it is time to continue to monitoring for diseases to make an informed decision if a fungicide is necessary. The hot and dry conditions a few weeks ago kept disease at bay, but recent rains have made conditions conducive for many of the foliar diseases in corn therefore it is now time to get out and scout.  As a reminder for disease to occur, three things need to be present 1. Pathogen, 2. Host, and 3. Favorable Environment. The major diseases we monitor in Indiana such as gray leaf spot, northern corn leaf blight, northern corn leaf spot, and tar spot all might start to make an appearance.

Corn Tar Spot Examples of corn leaves infected by tar spot. The spots (stroma, in black squares) will be embedded in the leaf, raised (bumpy to the touch), and will not rub/wash off. In addition, they may be surround by a slight halo. Photo Credits: Darcy Telenko