Common rust is caused by the fungus Puccinia sorghi. Late occurring infections have limited impact on yield.
The fungus overwinters on plants in southern states and airborne spores are wind-blown to northern states during the growing season.
Disease development is favored by cool, moist weather (60 – 70◦ F).
The use of resistant hybrids is the primary management strategy for the control of common rust.
Timely planting of corn early during the growing season may help to avoid high inoculum levels or environmental conditions that would promote disease development.
Symptoms of common rust often appear after silking.
Small, round to elongate brown pustules form on both leaf surfaces and other above ground parts of the plant.
As the pustules mature they become brown to black.
If disease is severe, the leaves may yellow and die early.
- Common Rust Fact Sheet (PDF)