Infection can occur on leaves as early as 1 week after planting. Sporulation (production of rust pustules) on leaves can occur about 3 weeks after planting. Each pustule can consist of few to thousands of yellow-orange uredia. Each uredium contains thousands of urediniospores which have a powdery appearance. In the seedling stage stripe rust forms patches, not stripes, and can form necrotic patches with/ without uredia. Urediniospores can be disseminated by wind to infect wheat, barley, and other grasses.
In the adult plant stage, uredia are often arranged into stripes. In severe infections, stripe rust pustules cover the leaf surface and stripes are not obvious. In later growth stages, stripe rust often produces black colored pustules (called telia) which are also arranged in stripes. Teliospores produced from telia cannot infect wheat, barley, and other grasses, but may infect barberry and mahonia.