Ash rust, caused by Puccinia sparganioides, is more of a curiosity than a real problem. Ash rust attracts attention because of the bright orange color of the fungus fruiting structures and the deformities which it causes on petioles and leaves. This rust alternates its hosts. The orange spores produced on ash do not reinfect ash but rather infect a wild grass (cordgrass, Spartina spp.). The spores produced in fall on the grass are responsible for infection of ash leaves the following spring. Since cordgrass often grows in wet areas or ditches, ash trees in the vicinity may show more severe rust.