WSR Pustules Through Seedling Leaf (IMAGE) University of Sydney Caption Superficially, stem rust looks like another rust pathogen of wheat, leaf rust. The two can be distinguished on leaves, with leaf rust forming pustules on one side of the leaf only, and stem rust producing pustules that appear on both leaf surfaces. Credit Credit Karanjeet Sandhu, University of Sydney. Usage Restrictions Must credit License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.