Farm Progress

Key discovery made in tar spot battle

This breakthrough could speed up development of tolerance to tar spot.

Tom J. Bechman, Midwest Crops Editor

May 15, 2024

3 Min Read
A close up of corn leaves with tar spot symptoms
HEAD-TURNING SYMPTOMS: The words “tar spot” are sure to catch a corn grower’s attention. Look at these classic symptoms. Photos by Bayer

Anyone born before 1960 likely knows what they were doing when Neil Armstrong stepped onto the moon. His words, “One small step for man, one giant leap for mankind,” still echo across the universe. If you grow corn, someday you might remember when you first read about the news you are about to learn. In the fight against tar spot, it could prove to be a turning point in the journey toward improved genetic tolerance and better management strategies.

Recently, Bayer Crop Science announced that its researchers artificially inoculated tar spot in field test plots. Until now, no one had accomplished that feat. Why does it matter?

“By creating field conditions for tar spot to take place, as well as inoculating the field artificially, we now have a reliable opportunity to study the environment and genetic response to the presence of the disease,” says Christian Heredia, Bayer Crop Science market development manager. “We can rapidly identify and promote new corn hybrids with enhanced tar spot tolerance, as well as enable breeding strategies to deliver more genetic potential.”

Big step forward

University researchers across the U.S. in Nebraska, Wisconsin, Minnesota, Indiana and elsewhere have worked diligently to learn more about tar spot since it appeared in the U.S. less than a decade ago. Tar spot, caused by the fungus Phyllachora maydis, was confirmed in 2015 in seven counties in northwest Indiana and 10 counties in north-central Illinois. Since then, it has spread in all directions from those initial discovery points. In years when weather conditions favor tar spot, it can easily knock off a sizable percentage of potential yield.

One roadblock hampering researchers until now was the inability to inoculate corn in test plots like pathologists do for most other economically important corn diseases. Bayer researchers previously replicated tar spot in greenhouses, but that doesn’t always correlate to how a plant will respond in the field, Heredia notes.

Jim Donnelly, a Dekalb technical agronomist, adds, “Our field testing allows us to inoculate tar spot wherever we place our plots to help us study and learn more about this potentially devastating disease.”

Pictured from left: Christian Heredia and Jim Donnelly

Tar spot management plan

Hybrids with more tolerance to tar spot will be key to managing this disease in the future. But improved hybrid tolerance alone isn’t the answer, researchers say. “Bayer is committed to delivering solutions when it comes to managing and controlling tar spot, both through continued genetic gains and innovations in our fungicide portfolio, to make sure we’re offering farmers multiple options for controlling diseases,” Donnelly says.

Donnelly and Cody Hornaday, Channel technical agronomist, emphasize that a holistic plan — which includes product selection and placement, scouting, applying fungicides when needed and using general disease management best practices — is necessary to manage tar spot successfully.

Bayer’s fungicide portfolio includes Delaro Complete, which offers three modes of action for providing consistent control of major corn and soybean diseases, including tar spot.

Information supplied by Bayer contributed to this story.

Read more about:

Tar Spot

About the Author

Tom J. Bechman

Midwest Crops Editor, Farm Progress

Tom J. Bechman became the Midwest Crops editor at Farm Progress in 2024 after serving as editor of Indiana Prairie Farmer for 23 years. He joined Farm Progress in 1981 as a field editor, first writing stories to help farmers adjust to a difficult harvest after a tough weather year. His goal today is the same — writing stories that help farmers adjust to a changing environment in a profitable manner.

Bechman knows about Indiana agriculture because he grew up on a small dairy farm and worked with young farmers as a vocational agriculture teacher and FFA advisor before joining Farm Progress. He works closely with Purdue University specialists, Indiana Farm Bureau and commodity groups to cover cutting-edge issues affecting farmers. He specializes in writing crop stories with a focus on obtaining the highest and most economical yields possible.

Tom and his wife, Carla, have four children: Allison, Ashley, Daniel and Kayla, plus eight grandchildren. They raise produce for the food pantry and house 4-H animals for the grandkids on their small acreage near Franklin, Ind.

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