All turfgrass grown in the Midwest are susceptible to one or more rust fungi. Most rust problems occur on Kentucky bluegrass, perennial ryegrass, tall fescue, and zoysiagrass.
Heavily infected grass becomes reddish brown to yellow-orange because of large numbers of powdery pustules. The rust material (countless rust spores) easily rubs off onto fingers, shoes, and clothing. Severe rust infection causes grass blades to turn yellow, wither, and die. Heavily rusted turf is thinned, weakened, and more susceptible to winterkill, drought, and other diseases.
Rust damage is usually minor except in mid to late summer when there are humid but dry periods with heavy dews (or improper watering tactics). Rust rarely kills mown turfgrasses, especially if they are kept growing steadily by proper watering and fertility.
To produce steady growth in dry weather, follow good cultural practices for the turfgrass species you are growing. Usually a light application of nitrogen fertilizer and one or more deep irrigations are sufficient. Resistant turfgrass varieties are available. Because there are different races of the fungus, a variety may be resistant in one location and susceptible in another turfgrass area. Applying fungicides preventively is effective where rust is serious year after year. Repeat applications are needed every 7 to 14 days, starting when rust is first evident.