Leaf smuts (stripe & flag smut)
Ustilago striiformis & Urocystis agropyri
Systemic smut fungi that stunt and streak older stands of Kentucky bluegrass, splitting leaves into ribbons that release black spore dust.
Identification
Pale-green to yellow, stunted, erect plants. Long yellow-green streaks run the length of the blade and sheath, turn silvery-gray, then rupture to release blackish-brown powdery spores; leaves curl and shred into ribbons from the tip down and die. Infected plants are systemically infected for life.
Symptoms
Stunted, pale, upright plants in spring/fall. Gray-black streaks along blades that rupture into black spore dust. Leaves curl, shred into ribbons, and die back
Signs
Pale-green to yellow, stunted, erect plants. Long yellow-green streaks run the length of the blade and sheath, turn silvery-gray, then rupture to release blackish-brown powdery spores; leaves curl and shred into ribbons from the tip down and die. Infected plants are systemically infected for life.
Biology
Leaf smuts are systemic fungal diseases caused by Ustilago striiformis and Urocystis agropyri. Infected plants remain systemically colonized and produce dark spore masses in streaked leaf tissue.
Epidemiology
Cool temperatures (10-20°C), low soil moisture, soil pH below 6.0, and older stands (2+ years) of susceptible cultivars. Spreads slowly; stressed plants die first.
Favorable Conditions
Cool temperatures (10–20°C), low soil moisture, soil pH below 6.0, and older stands (2+ years) of susceptible cultivars. Spreads slowly; stressed plants die first.
Cultural Management
Renovate/overseed with blends of several resistant cultivars. Avoid excess nitrogen in summer; irrigate to limit drought stress. Avoid prolonged leaf wetness
Further Reading
University extension resources — open in a new tab.
Related Reports
No published reports yet for this pest.
Reports will appear here as they are peer-reviewed and published.