Southern Rust in Kentucky Corn

Joanna visits with Dr. Kiersten Wise, Extension Plant Pathologist to discuss Southern Rust in Kentucky Corn.
It has been a couple of weeks since our first confirmation and southern ruse has been spreading in the state. It is now confirmed in central Kentucky, as far east as Nelson County. In western KY, severity is still low, but incidence is increasing. Southern ruse is characterized by pustules that are cinnamon brown, circular to oval, and densely scattered on the upper leaf surface. We are confirming the disease in more fields, but fortunately, most corn is far enough along to not be significantly impacted. However, some later planted fields and fields in central and eastern KY will still need to be scouted and monitored carefully to determine if fungicides are needed to protect yield from southern ruse. Southern ruse is caused by the fungus Puccinia polysora. Development of the disease is favored during periods of high temperature (80 degrees F) and high relative humidity. Southern rust does not occur as often from year to year as does common rust. On susceptible hybrids, the disease can develop very rapidly during warm, humid conditions.
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Warren County Cooperative Extension Service