Dakota Farmer

Scout 2024’s corn diseases this yearScout 2024’s corn diseases this year

Tar spot, smut, rust, leaf blight, Goss’s wilt and more expected this growing season.

Elizabeth Hodges, Staff Writer

January 13, 2025

3 Min Read
disease on corn
WATCH OUT: Scout early and often for diseases in corn fields. If a disease was an issue in 2024, it is likely to return in 2025.Stefani Reynolds/Getty Images

One way that producers can improve their scouting efforts is by looking back at the diseases that were prevalent in fields the year before. By thinking about these pesky diseases early on, management decisions can be made to set up the upcoming growing season for success.

Andrew Friskop, a cereal crop pathologist at the North Dakota State University Extension, reflects on the top five corn diseases that inhabited fields in the state and warns of the arrival of tar spot.

Top 5 corn diseases in fields

Although some corn diseases are detrimental for fields, not all are an economic disease. However, it can be helpful to understand the current disease environment in your area.

  1. Corn smut made an appearance in North Dakota fields in 2024 and was the highest occurrence of the disease in the last 10 years. Although there is no need for concern or treatment of this disease at this level, Friskop reports that there was corn smut in 22% of fields in the state in 2024.

  2. Common rust was found in 96% of North Dakota fields last year. However, there was minimal loss due to this disease because of the current hybrids that are being grown. Fungicides work well to eliminate common rust; however, Friskop doesn’t recommend applying these fungicides because of the hybrids commonly used. Rust pressure was most prevalent in September, when Southern rust showed up, but this disease came late in the season and was not damaging.

  3. Northern corn leaf blight can be economically damaging to fields. However, Friskop reports that in North Dakota, the risk for yield loss is low even though it was present in 36% of fields across the state.

  4. Bacterial leaf streak is a blemish disease that was present in 9% of corn fields. But this disease does not have a long shelf life when sitting on residue, so Friskop is not worried about it carrying over to this year. One rotation away from the previous crop should break this disease cycle.

  5. Goss’s wilt was the No. 1 concern in North Dakota in years past. Friskop says that even after five years of management, there was still a 56% occurrence of this disease. However, 2024 brought good news of only a 7% occurrence, revealing a good management success story.

Related:Top corn, soybean and wheat diseases to watch in ’25

Tar spot’s not so warm welcome

Across the Midwest, tar spot has been appearing in fields. However, 2024 was the first year that tar spot made an appearance in North Dakota. This fungal leaf disease defoliates and disrupts nutrient flow, which leads to yield loss. Friskop says the perfect breeding ground for this disease is temperatures between 64 and 73 degrees F and wet conditions.

Related:Want to preserve corn yield by more than 50%?

The 10 counties in the eastern corner of the state were the first to encounter tar spot in the state. Although it arrived late in the season, Friskop predicts that this could overwinter and show up next growing season.

This relatively new disease shows up as an irregular or diamond-shaped lesion that has a spore in the middle. There are different field materials that show up that might try to mimic the appearance of tar spot. Insect frass, dried mud and overwintering rust at first might appear to be tar spot when scouting. However, the key signs to decipher tar spot are that it is slightly raised and does not rub off. The rest of these imposters might be shiny, rub off when touched or appear to be shredded. These are not signs of tar spot.

“In the future, we are going to be putting a heavy investment and focus on tar spot research,” Friskop says, “trying to see if tar spot overwinters, having different hybrids to have a general sense of susceptibility and different fungicide programs.”

When picking out the perfect hybrid or scouting for the next growing season, it is important to keep these prevalent corn diseases in mind to increase yield.

About the Author

Elizabeth Hodges

Staff Writer, Farm Progress

Growing up on a third-generation purebred Berkshire hog operation, Elizabeth Hodges of Julian, Neb., credits her farm background for showing her what it takes to be involved in the ag industry. She began her journalism career in high school, reporting on producer progress for the Midwest Messenger newspaper.

While a student at the University of Nebraska-Lincoln, she became a Husker Harvest Days intern at Nebraska Farmer in 2022. The next year, she was hired full-time as a staff writer for Farm Progress. Elizabeth graduated from UNL in 2024 with a double major in Agriculture and Environmental Sciences Communication and Animal Science.
Hodges’ father, Michael, raises purebred Berkshire hogs, and her mother, Christy, is an ag education teacher and FFA advisor at Johnson County Central. Hodges is the oldest sibling of four.

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