Crown rust of oats is caused by the fungal pathogen Puccinia coronata. It infects Canadian Oat crops nearly every year and can lead to 100% yield loss if environmental conditions favor the infection and there is a high density of fungal spores. Infection in Canada has been most severe in South Eastern Saskatchewan and Manitoba.
Symptoms of the disease are the formation of distinctive orange pustules of spores developing on the oat leaves. The formation of these pustules can be present as early as late April. Lesions may also be present on other plant parts; however, leaves are the favoured area for pustule formation.
Look for orange pustules that form on both the upper and lower surfaces of the leaves. When infection is severe, sheaths and glumes can also become infected. As the infected plant matures, the pustules darken to black. Spores released from the pustules will soon infect neighboring plants, enhancing the importance of preventative control, and a clear epidemiological approach for the management and control of this disease.