Stripe rust of wheat
Stripe rust can occur anywhere in the U.S. and Canada, causing substantial yield losses when conditions are favorable. It is caused by Puccinia striiformis and is also known as yellow rust. Initially, symptoms are yellowish flecks on leaves. On susceptible varieties, pustules containing yellow-orange spores erupt from leaves. Pustules are clustered on seedling leaves, while pustules on mature leaves occur in a linear, stripe-like pattern. Later in the season, yellow-orange fungal spores turn black and remain attached to leaf tissue. Symptoms can be present from seedling stages through ripening. Stripe rust pustules form a noticeable striped pattern on mature leaves and are more yellow than stem rust spores.
The fungus causing stripe rust does not readily overwinter in areas with temperatures below 14°F without snow cover. Spores are blown from areas where the fungus survives and begin new infections when they land on leaves. In general, disease development is favored by wet and cool weather. The infection cycle will continually repeat and result in secondary infections, and disease intensity can quickly reach epidemic levels if weather remains favorable.Yield loss in the U.S. Great Plains and Canada will depend primarily on timing of spore migration and weather conditions when spores arrive in an area.
Plant wheat varieties with resistance to stripe rust. Avoid over fertilization and excessive irrigation; planting date may also help reduce the risk of stripe rust, as will controlling volunteer wheat especially where warm winters occur. Fungicides are labeled for stripe rust management and should be applied preventively to protect the flag leaf (FGS 8-10). Scout and consider factors such as varietal susceptibility, forecasted weather, and yield potential prior to fungicide application.
Gallery images: C. Grau