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K-State Turfgrass

Smut on the internet. (Wait – what? Oh – leaf smut)

(Megan Kennelly, KSU Plant Pathology)

The following photos were kindly shared with me by Peter Orwig, Agronomist with Ryan Lawn and Tree (thanks Peter!).  You can click to zoom and see the symptoms close up.

Peter-Orwig-stripe-smut-2015-05-07 08.34.32  Peter-Orwig-stripe-smut2015-05-07 08.34.46 Peter-orwig-stripe-smut-2015-05-07 08.35.51 Peter-Orwig-stripe-smut-2015-05-07 08.36.57

There are several “leaf smut” fungi that occur in turf. The most common is stripe smut, but flag smut also occurs. The disease causes stunting and yellow or gray streaking along the leaves. Eventually those streaks rupture, releasing powdery masses of smutty, sooty black spores. When a plant is infected, it is infected systemically, for life. Infected plants are more susceptible to drought and other stresses.

Flag smut and stripe smut are difficult to tell apart at the plant level, but they are easy to distinguish in the microscope. Smut fungi can look similar, but they are different in various ways, including host range. For example, flag smut occurs in Kentucky bluegrass but not annual bluegrass. And the flag smut that occurs in Kentucky bluegrass is different from the flag smut that occurs in wheat and other grasses. In Kansas, we see leaf smuts most often in older varieties of Kentucky bluegrass. The best way to prevent leaf smuts is to use improved variety blends with resistance to these diseases. Spring and summer applications of nitrogen may increase smut, so focus on fall applications if smut is a problem. In addition, smut-infected turf might need to be babied along during times of drought. If smut is severe, your best bet might be to just start over with newer resistant varieties.

*If you come across smut in turfgrass, send me an email (kennelly@ksu.edu) because I’m  interested to collect some this year. *