Rust is a fungal disease caused by several species of Puccinia. All turfgrass species are susceptible to rust. However, it is most commonly seen on perennial ryegrass and Kentucky bluegrass.
From a distance, rust infected turf has a yellow-brown color. Close examination of rust-infected grass blades reveals numerous yellow-orange pustules. Rust can be easily diagnosed by walking across the lawn. As one walks across the lawn, bright orange spores of the rust fungus rub off onto one’s shoes.