STRIPE SMUT ON TURFGRASS   F A C T S H E E T

Introduction

In the late spring or early fall some lawns exhibit yellow or brown stunted areas which are not necessarily confined to patches. Close examination may reveal that this unhealthy look is due to stripe smut, a common disease of bluegrasses, bentgrasses, fescues, perennial ryegrasses, and other grasses. Other smut fungi also attack various grass species. During very hot dry periods however, the striped smut infection may become severe enough that individual plants are killed. During wet summer weather, a striped smut infection may weaken plants enough that a simultaneous invasion by other disease organisms may also cause plants to die.

Symptoms

Unless a large area of turf is dying, an overall view of the infected turf area may not be very revealing. However, infected grass blades, when viewed closely, will display yellow-green streaks in the early stages of disease, and these streaks later become gray. Shortly afterwards, the leaf tissue over the gray streaks ruptures and black spore masses are exposed (Fig. 1). After rupturing, the diseased leaves become shredded into ribbons (Fig. 2) and curl downward from the tip. The grass blades then become dark brown and die.

Figure 1: Black spore masses in streaks on the leaves   Figure 2: Leaves become shredded after spores are exposed.

Disease cycle

The disease becomes evident in the 10°C to 16°C (50°F to 60°F) weather of spring and fall. Infected plants growing at higher temperatures for extended periods will usually die, leaving only the noninfected shoots; consequently, visual symptoms are seldom present during midsummer. The dark spores produced in "stripes" along the leaf blades serve as a survival stage for the smut fungus during the summer and winter. Also, the fungus may survive as mycelium in infected crowns and rhizomes.

In spring and fall, when environmental conditions are satisfactory, the dormant spores will germinate and produce another form of spore which can infect the grass plants. Spores are spread by wind, water, maintenance practices, animals, and people.

Management Strategies

Some varieties of bluegrass survive the effects of the disease better than others. Merion Kentucky bluegrass, for instance, is very susceptible to stripe smut, while Park and Newport are fairly resistant. Other more resistant varieties are A-20, A-34, Aquila, Baron, Birka, Bonnieblue, Fylking, Geary, Glade, Nugget, Pennstar, South Dakota Certified, Sydsport, Vantage, and Victa.

Optimum fertilization with a complete (not nitrogen only) fertilizer and conscientious watering helps maintain the vigor of the stand and to increase the survival of infected plants.

Systemically-translocated fungicides are helpful for controlling the stripe smut disease. Applications are to be made just prior to dormancy in the fall (November in much of New York) or just before growth resumes in the spring (March). The fungicide should be drenched into the turf with at least 1/2 to 1 inch of water.
Systemic fungicides available for use by homeowners include those containing the active ingredients triadimefon or thiophanate-methyl.

Additional products may be available for use in commercial plant production. Commercial applicators should refer to the appropriate pest management guidelines for more information.

Updated , SLJ, 4/05