Southern rust confirmed in southeast Nebraska
C. SchleicherFigure 1. Southern rust spores are typically orange to tan in color and produced in pustules predominantly on the upper leaf surface, although they can also be produced abundantly on/near the midrib on the underside of the leaves. Southern corn rust (Figure 1) has been confirmed in a sample from Otoe County in southeast Nebraska by a diagnostic laboratory at DuPont Pioneer.
At this time, this is the only confirmation of southern rust in Nebraska. Southern rust is widespread across many counties in the southern US, creating an abundance of spores that could move north to our area and cause more disease. Warm temperatures, high humidity, and winds from the south may promote development and spread of the disease.
Having a history of southern rust in corn has no impact on disease development this year because this pathogen does NOT overwinter in infected residue. Spores are windborne and must be carried into the area from southern or western disease areas.
If the disease continues to spread and worsen in Nebraska, those fields planted later are at highest risk for disease and potential yield reductions. We recommend scouting fields, especially those at higher risk, now. High risk fields include those planted (and replanted) later in southern Nebraska counties.
We will be monitoring the development of southern rust in Nebraska and reporting it by county on the IPM PIPE Southern Corn Rust monitoring website.
NOTE: Not all states participate in updating the maps on this website. Thus, the maps on the website may not be up-to-date, and so they should not be strictly relied upon for disease confirmation and incidence. Refer to the reports from local university plant pathologists, diagnostic laboratories and county Extension offices for the most recent information regarding southern rust distribution.
Is it Southern or Common Rust?
The characteristics used to differentiate between common rust and southern rust are described and illustrated in the NebGuide, Rust Diseases of Corn in Nebraska (G1680). The simplest and most reliable way to differentiate the diseases without a microscope is to examine both leaf surfaces for spore production. Southern rust spore production is usually limited to the upper leaf surface and tends to be tan/orange in color.
The most reliable method for identifying corn rust diseases is examination of the microscopic spore characteristics. Samples can be submitted to the UNL Plant and Pest Diagnostic Clinic for diagnosis.
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