The season’s first cases of tar spot in South Dakota have been confirmed in Union, Clay, Yankton, Lincoln, Turner, and Minnehaha counties, according to the latest map published by the Crop Protection Network. The foliar disease was first confirmed in the state on Sept. 2 in Clay County.
Forty-six of the state’s 66 counties have a history of tar spot since it was first detected in South Dakota in 2022.
Timing
Here’s a timeline of how the disease has been detected in the state:
- Sept. 2 – Clay County
- Sept. 4 – Union County, Yankton County, Turner County
- Sept. 9 – Lincoln County, Minnehaha County
Cases have also been reported this year in the following states:
- Delaware
- Georgia
- Illinois
- Indiana
- Iowa
- Kansas
- Kentucky
- Michigan
- Minnesota
- Maryland
- Missouri
- Nebraska
- New York
- North Carolina
- Ohio
- Pennsylvania
- Virginia
- Wisconsin
Expert Report
“The fields I saw [Tuesday], it was very easy to find one or two lesions on a few leaves per plant, but not severe,” said Madalyn Shires, South Dakota State University plant pathologist. “It was kind of widespread, but very low incidence and severity across fields.”
As Shires traveled north, tar spot wasn’t nearly as widespread. What was confirmed were “definitely early cases because it was hard to find in the fields,” she said.
Weather Recap
Like much of the rest of the Great Plains, the state had prevailing droughts up until four to six weeks ago, Shires explained. Around the first week of August, she and her team noted increasing humidity and periodic rain events. “We kind of expected tar spot to start showing up, and it did,” Shires said…