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Smut — Ustilago striiformis, Urocystis agropyri

© 2017 MSU Plant Pathology
© 2017 MSU Plant Pathology
© 2017 MSU Plant Pathology
AKA

The smut diseases are important on many Kentucky bluegrass cultivars and higher cut turfgrass. Individual infected plants may be found in a stand of turf, or large patches of infected plants may form. Infected plants tend to not grow as profusely as healthy plants, with stunted growth and stiff, erect leaves rather than relaxed spreading leaves. Light yellow blades of grass are evident during the initial phase of the disease, and as symptoms advance, leaf blades begin to curl and show black stripes running the length of the blade. Older infected blades appear twisted, curled, and shredded from the tips down.

The fungus overwinters as mycelia in infected plants, and infection is thought to occur in the cool wet weather of the spring and fall. Symptoms are most commonly seen in the spring and fall when the temperature is below 70° F (21.1° C), and gradually disappear as the weather becomes warmer. Extensive turf loss occurs during hot, dry summer weather, when grass is under heat or drought stress.