Written collaboratively by Madalyn Shires, Cody Molnar, Connie Strunk, and Dalitso Yabwalo.
Recent Southern Rust Reports
In late July, reports began about possible Southern Rust on corn fields in several South Dakota counties. Upon scouting, we were able to confirm that the disease was found in Clay, Yankton, and Bon Homme counties (Figures 1 and 2). We received pictures of southern rust, which was confirmed in Union County. We also observed extremely early disease development in Brookings, Moody, and Deuel counties (one or two lesions on a few plants in the scouted field).
Scouting and Management
Southern rust appearing this early in the growing season (tassel to silk stage) is rare for South Dakota and may require fungicide applications to reduce disease impacts. Yield impacts from Southern Rust can be high, so scouting for the disease is needed to determine if it is present (Figure 3). Current weather conditions of high humidity and frequent rainfall can encourage rapid disease development. Corn grown in irrigated fields should be scouted frequently and carefully as those fields are the most likely to have yield losses.
There are fungicide options for management of this disease. Please refer to the most-recent South Dakota Pest Management Guides for more information and a full list of options. Consult the fungicide label for application timing and crop growth stage. For a better understanding of average efficacy of fungicides for southern rust and other corn diseases, see the Crop Protection Network’s Fungicide Efficacy for Control of Corn Foliar Diseases resource.
