Farmers who are watching for the development of tar spot in Corn Country are beginning to see some areas starting to light up with the disease.
“It’s in Michigan, a lot in Indiana, Ohio, even into Wisconsin and Iowa, so there’s definitely tar spot pressure starting to happen,” says Missy Bauer, Farm Journal Field Agronomist and owner of B&M Crop Consulting, Coldwater, Mich.
She addressed the issue this week at the 2024 Farm Journal Corn & Soybean College at Heyworth, Ill.
Bauer wants to get the word out to corn growers that evaluating weather information now – especially average daily humidity levels – signal that you need to prepare for tar spot and put your fungicide application plan together.
You can find the average daily humidity information for your specific area online via Weather Underground and other weather station resources.
Charting Humidity Levels Is Easy
To use the information, Bauer recommends setting two benchmark years, using 2021 and 2022 weather data. The reason for that: 2021 was a high-pressure year for tar spot in much of the U.S. corn growing area, whereas 2022 was a low-pressure year. Learn more in the video Bauer did to explain the process.
She gives you an idea of how to set up the information for tracking purposes. The chart shows you the weather data she has tracked from June 1 through July 22 over a four-year period – 2021 through 2024.
Bauer is concerned that 2024 could see some significant problems from tar spot, because of the higher humidity levels she is seeing this season in the Midwest. Tar spot levels this year for her area, south-central Michigan, are higher than they have been for the previous two seasons.
“While it’s not as bad yet as in 2021, we’re tracking on those higher levels this year,” she says. “As you get daily humidity averages that hang at 75% or above, it’s going to increase the chances we’ll end up having tar spot.”
Corn growers will need to track the weather data for their specific area to evaluate what kind of potential risk their crop could face.
For additional reference, corn growers can get an idea of where tar spot is showing up by county via the website ipmpipe.org/tarspot/ This site is maintained by a combination of university Extension and agriculture industry members.
“Corn growers need to be alert and on-guard, and start scouting for tar spot,” Bauer says. “Make your decisions on fungicide timings and what you’re going to do to treat, and have all your plans in place. The weather data is certainly telling us to be ready for tar spot.”
For additional insights on tar spot:
Tar Spot Disease Pressure Is In the Forecast Now
You Can’t Afford to Be Complacent About Tar Spot
How to Time Fungicide Applications To Best Tackle Tar Spot
