Rust on Lawns
Rust on turf is caused by the fungus. It can be a problem with all turf grasses, but it commonly attacks Kentucky bluegrasses, ryegrasses, and zoysia.
Turf that is infected with rust will turn light green and then begin to have an orange or reddish cast. The orange powder is actually millions of microscopic spores that can rub off on fingers, shoes, or clothing. Leaves that are heavily infested with rust pustules can wither and die. Lawns that are continually under attack from rust are more likely to suffer winter damage. Areas that are heavily shaded tend to be the hardest hit with rust.
Rust on leaf surface. Picture by B. Fresenburg
Conditions that favor the development of rust are two or three consecutive overcast days, temperatures in the 70's, lawns that have low fertility, and heavy dew formation.
Control measures against rusts are to irrigate infrequently and deeply and fertilize the turf as needed. Mow regularly and at the recommended height.
If the rust is heavy, remove the clippings when mowing to remove the source of infection. Pruning trees to increase light penetration also aids in reducing the rust populations.
A mixture or blend of grass seed or sod also reduces the chances of a severe rust outbreak. Several fungicides can be used, but normal cultural practices will generally take care of the rust.