What are the first visible signs of Necrotic Ring Spot?

The first visible signs of Necrotic Ring Spot are indeed circular patches of dead grass. This fungal disease manifests primarily as distinct, often circular areas where the grass has died off, typically leaving a ring of healthy grass around the periphery. These patches can vary in size and are most commonly observed in the spring and fall, when environmental conditions are favorable for the disease to develop.

In contrast, the other options represent symptoms of different turfgrass issues. Small brown spots on leaf blades are more indicative of issues such as leaf spot diseases or environmental stress. Pinkish-red threads on leaves could suggest the presence of certain diseases or pests, such as turfgrass webworms, but they do not specifically relate to Necrotic Ring Spot. Lastly, white cobwebs in the morning dew are usually associated with other fungal diseases or spider activity, not Necrotic Ring Spot. Understanding these distinctions is crucial for effective turfgrass management and disease identification.