Samples with ash rust have recently been submitted to the Plant Disease Clinic. The fungus that causes this disease, Puccinia sparganioides, can infect different types of ash trees. Yellow to orange pustules cover the misshapen leaves, petioles, and small twigs of the infected tissues.
This fungus appears more threatening than it is because of the noticeably bright color of the pustules. In Iowa, controls are rarely needed because the fungus typically does little damage to the tree. Cord or marsh grasses are required for the fungus to complete its life cycle, overwinter, and re-infect ash trees.
For images of ash rust visit the Plant Disease Clinic website , select the Plant Diseases option, then Broadleaf Trees, and Ash Rust.
This article originally appeared in the 6/18/2004 issue.