Asco what?! That’s the immediate response I get from turfgrass managers when I tell them I just diagnosed their damaged tall fescue sample as Ascochyta leaf blight. Even though we don’t see this disease with the same frequency as brown patch, Pythium blight, or gray leaf spot in tall fescue, it demands respect in the world of turfgrass pathology. We typically diagnose a few cases of this disease every spring in North Carolina and have already confirmed a few positive sites within the past week. This might be the disease you’ve overlooked in past springs and is worth learning more about if you want to improve your management skills of tall fescue.
Ascochyta leaf blight is caused by nearly 80 different species of Ascochyta. This fungus has been documented on many turfgrasses, but more common on tall fescue, Kentucky bluegrass, and perennial ryegrass. As the name implies, the primary symptom is blighted leaves. The pathogen only attacks the foliage; therefore, damage is seldom permanent and recovery is quick under favorable growing conditions. As seen in Figure 1, stand symptoms may rapidly encompass large areas of uniformly blighted, straw colored turf. Individual leaves typically start dying from the tip back and bleached lesions may eventually develop along the entire leaf blade. .