Text adapted from Turfgrass Pest Management: A Guide to Major Turfgrass Pests in Oklahoma. Oklahoma Cooperative Extension Service.

CAUSE: The rusts include several important diseases caused by obligate fungal parasites, primarily species in the genus Puccinia.

HOSTS: Rust diseases can occur on all turfgrasses.

SYMPTOMS: Early symptoms include small yellow spots that develop on the leaves and stems. The infected spots enlarge and develop into orange and red blisters that rupture and release masses of yellow, orange, red or dark brown spores (Figure 1).
When rust is severe, infected turfgrass may appear red, brown, or yellow, depending on the particular rust fungus causing the disease, and it becomes thin and weakened (Figure 2).

DISEASE CYCLE: Infected turfgrass foliage in areas with mild climates serves as the overwintering site for rust fungi. When the weather is conducive for spore germination, new infections begin. These, then, produce millions of spores that can be transported over long distances by wind. Spores from warm regions then spread by wind to produce disease infections in colder regions.

FACTORS FAVORING DISEASE DEVELOPMENT: Rust diseases usually become more severe on turfgrasses that are growing slowly due to stress. Typical stresses include drought, nutrient deficiency, low mowing height and shade. Leaf wetness is necessary for spore germination and for rapid disease development.

CONTROL: Irrigate and fertilize the turfgrass as needed to avoid water- and nutrient-related stresses that impede turfgrass growth. Watering deeply, but infrequently, in the early part of the day will encourage deep rooting, reduce drought stres s and avoid extended periods of leaf wetness.
Mowing regularly to sever the infected leaf tips before spores are formed, or become mature and are released, will reduce the spread of these diseases.
Selectively prune trees and shrubs to improve the penetration of sunlight into densely shaded areas and to improve air circulation.
Several fungicides are available for controlling severe rust infections.

Figure 2. -- "Yellowish orange cast on large area of turfgrass as a result of infection by rust fungi", Courtesy of C.S.S.A.