There are a couple of ways you can do this. Let’s keep it simple by focusing on one problem to rule out the other.
- Round patches with more of a “bluish” tint is usually early sign of a fungal problem.
- If these patches are browning out quickly, pull a leaf blade and examine it closely to check for dark, round spots. These spots are lesions caused by fungal pathogens.
- If the patches are not blue tinted and you cannot find lesions on the leaf blades, it must be drought stress, not fungal issues.
- Drought stress does form the same rounded patches but turn more grayish and die quickly without water. These dead patches are crispy with no lesions present on the leaves.