Rust Disease favors warm and humid conditions and develop most frequently on grasses subject to drought-stress conditions, low nitrogen fertility and shade. Low mowing heights, particularly on Kentucky bluegrass, also increase the susceptibility of grasses to rust.The disease first appears on grass leaves as small orange to reddish-brown flecks that enlarge to form raised pustules on leaves and stems (these are what turns shoes and socks orange). Individual pustules are usually oval or elongated and contain a powdery mass of orange to reddish-brown spores. As the pustules mature they turn brown to black. Heavily infested turf becomes thin with an overall yellow-orange to reddish-brown color. Infected leaves turn yellow, wither and die. Cultural practices which improve the vigor of the turf help prevent rust. To reduce the incidence of rust, keep nitrogen levels adequate for turf growth, avoid moisture stress or over watering and adjust mowing heights according to the grass needs.