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Rust and Smut Diseases

Rusts: Crown, Leaf, Stem, and Stripe

Causal Agent: Crown—Puccinia coronata; Leaf—Uromyces dactylidis; Stem (Black)—Puccinia graminis; Stripe (Yellow)—Puccinnia striiformis

Susceptible Turfgrass: Kentucky bluegrass, annual bluegrass, ryegrass, old bentgrass cultivars, zoysiagrass, bermudagrass, and tall and fine fescue

Symptoms: Rust diseases cause light yellow flecks initially on the leaf blades and sheaths. The flecks enlarge, elongate, and turn yellow in color. The infected areas rise above the epidermis and then rupture, releasing spores that are yellowishorange to reddish-brown in color. The leaf blade turns yellow starting at the tip and progressing to the base sheath. A severe disease infection can cause the shoot to turn yellowish to reddish-brown in color and slow in growth. The turf may appear thin as individual shoots die.

Conditions Favoring Disease: Rust diseases typically occur in early spring through fall, depending on the location of the turf. Rusts favor moist, low-light areas. Depending on the species, rusts favor temperatures between 65°F and 86°F. Severe rust infections occur on slow-growing turfgrass, particularly those with low nitrogen levels and/or plant water stress.

Management Tips:

  • Convert to a turfgrass species or cultivar (especially for Kentucky bluegrass and perennial ryegrass) that are resistant to rust diseases found in the area.
  • Apply adequate levels of nitrogen.
  • Remove clippings from turf.
  • Reduce thatch.
  • Reduce shade and improve air circulation.
  • Regulate irrigation to minimize the amount of time moisture remains on the leaf surface. Water deeply and infrequently.
  • Use systemic fungicides to control rust diseases on slow-growing grasses and to grasses that are not mowed.

Frequently occurs in: All states.

Labeled products:

Stripe Smut

Causal Agent: Ustilago striiformis

Susceptible Turfgrass: Annual bluegrass and certain varieties of Kentucky bluegrass, perennial ryegrass, and bentgrass

Symptoms: Plants are stunted and may appear light green or yellow. Leaf blades are stiff, erect and sheaths develop narrow, elongated streaks that are yellowish-green in color. The leaf blade then curls and forms parallel stripes that are gray to black in color and extend the length of the leaf. Infected older leaves will shred, twist, and split, starting at the tips and progressing downward. Infected areas may be concentrated in large areas or scattered across the turf. Eventually, the root growth and tillering of the turf are reduced.

Conditions Favoring Disease: Stripe smut favors temperatures between 50°F and 60°F, typically in the spring and fall. Hot, dry weather and improper fertilization accelerates the disease in older turf.

Management Tips:

Convert to a turfgrass species or cultivar (especially in Kentucky bluegrass) that is resistant to stripe smut.

Avoid high levels of nitrogen, especially during the summer.

Maintain a balanced fertility level.

Irrigate as needed to prevent drought stress.

Occasionally occurs in: AR, CA, DE, KS, KY, MD, MO, NV, OK, TN, VA.

Frequently occurs in: CO, CT, IA, ID, IL, IN, MA, ME, MI, MN, MT, ND, NE, NH, NJ, NY, OH, OR, PA, RI, SD, UT, VT, WA, WI, WV, WY.

Labeled products:

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