Different types of turf and ornamental grasses are affected by rust disease. Caused by a fungal infection, rust may severely damage your grass. Through proper maintenance and understanding what symptoms to look for, it is possible to control lawn rust through preventive and cultural measures; fungicides may also be used as diagnostic treatment when rust is already in place.
Commonly referred to as leaf rust, crown rust, lawn rust and stem rust, rust disease is a fungal infection caused by the fungi Puccinia spp., Uromyces spp. and Physopella spp. Often occurring more prevalently during warmer temperatures and high humidity levels, rust prefers a daytime temperature range of 85 to 95 degrees Fahrenheit and a nighttime temperature range of 70 to 75 degrees Fahrenheit. An easy diagnosis is the appearance of a rust-hued cloud that forms just above grass after mowing or rust-hued residue present on shoes after walking through the lawn. When rust disease infects grasses, the lawn changes to a light green color and then becomes a rusty red-orange, as though rust is forming on grass blades.
Grasses that are more vulnerable than others to lawn rust disease include turf grass mowed to a tall height, residential and athletic areas, and particularly ryegrass varieties, zoysia and Kentucky bluegrass. Shaded grass is much more susceptible than grasses in areas with high sun exposure. Additionally, lawns already stressed, infected with rust or other problems, or in decline due to poor maintenance are more likely to suffer from infection.
Damage and Disease Life
Lawn rust spreads through the distribution of spores that invade plants through pores or wounds. Rust disease may cause grass to change from the initial light green color to a yellow hue. After yellowing, rust causes stunted growth and often leads to plant death. Symptoms and subsequent damage most often show up late in the summer season and the beginning of the fall season; however, on grasses that are already malnourished or stressed, the disease may appear as early as spring.
Lawn Rust Treatment
Maintain your grasses based on their particular care requirements for vigorous resistance to disease. Plant resistant varieties to avoid infection. Always fertilize with a balanced fertilizer of nitrogen, phosphorus and potassium for consistent growth, create an environment with good air circulation and adequate sun exposure, keep grasses watered during morning hours in periods of drought, and keep grasses mowed to appropriate lengths; gather and destroy clippings to remove chance of reinfection or disease spread. Though fungicides are generally not necessary, in cases of severe infection, use sterol-inhibiting fungicides when rust is present for three or more simultaneous years; fungicides are best used as a preventive measure. Apply treatment the moment you notice rust and reapply every one to two weeks until symptoms subside, as directed by the University of Illinois Extension IPM.
Rust-Resistant Grass Varieties
The planting of rust-resistant grass varieties ensures that you will have a healthy lawn with no incidence of lawn rust. Resistant varieties include, but are not limited to, fescue grass cultivars Flyer and Shadow; perennial ryegrasses Prelude, Tara and Yorktown; and Kentucky bluegrass cultivars Adelphi, Aerica, Aquila, Bonnieblue, Bristol, Brunswick, Challenger, Enoble, Fylking, Holiday, Majestic, Midnight, Ram I, and Victa, according to the University of Illinois Extension IPM.