Rust fungus is fairly easy to identify on grass. It looks like a rusty powder and may cause the lawn to turn yellow, orange, red or brown. After walking on a lawn infected with rust fungi, shoes might have the yellow or orange powder on them. The disease eventually causes grass blades to develop raised pustules.
This fungus usually shows up during hot weather. Bluegrasses, ryegrasses, zoysia grass and tall fescues are all susceptible to rust, although some Kentucky bluegrasses and tall fescues are resistant.
The best most effective treatment for rust is to keep a lawn growing vigorously, fertilize it with nitrogen and water the grass in the morning.
Avoid light, frequent irrigation and instead water the lawn deeply and less frequently. Mowing regularly can help reduce the amount of rust fungi in the grass, as can removing thatch buildup with a rake.