Tar Spot Appeared in South Dakota Corn Fields
The fungal disease persists in the state, though it currently poses no significant threat to crop yields.
Updated on Oct. 8, 2026 in Botany
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Tar spot, a fungal disease, was first officially identified in South Dakota in 2022, though reports suggest the pathogen may have been present as early as 2021. Despite concerns, South Dakota has avoided the yield losses and lodging issues seen in other regions like Missouri.
Why it matters
Farmers in South Dakota continue to monitor for the disease, which historically impacts corn in other regions. Extremely dry environmental conditions in 2026 limited the prevalence of most corn diseases, including tar spot, throughout the state.
Tar spot is a saprophytic fungus—a microorganism that feeds on dead and decaying organic matter—that remains localized without causing the economic damage seen in other states. Fungicide application is only recommended if the disease is detected at the R2 growth stage or earlier.
The players
South Dakota
A major agricultural state where farming operations are currently monitoring for the spread of tar spot.
The details
Tar spot manifests as small black spots on corn stalks, acting primarily as a saprophytic agent on crop residue. Unlike fungi such as Fusarium and Aspergillus, which produce mycotoxins—poisonous substances that can lead to grain rejection at elevators—tar spot has not triggered such issues in South Dakota. While other regions experience severe lodging—when corn stalks bend over and break, making harvest impossible—South Dakota has remained free of these structural failures.
Timeline
2021: Reports suggest tar spot may have first been present in South Dakota.
2022: Tar spot was first formally identified in South Dakota.
2026: Dry conditions resulted in low levels of corn diseases across the state.
The Tech Race
The regional trajectory of this disease highlights the divergence between South Dakota and areas like Missouri, where impacts have been severe. South Dakota's experience serves as a contrast to established agricultural precedents in states facing higher fungal disease pressure.
Farmers currently face no disruption to grain sales or elevator processing due to the disease. Management remains focused on monitoring and timing potential fungicide applications to the R2 growth stage.
The takeaway
Tar spot remains a manageable presence in the state rather than a widespread threat to local harvests. Growers should continue to track environmental moisture levels, as these conditions remain the primary driver for fungal growth and mycotoxin development.
Further reading
Learn more about agricultural disease management in our Botany section.
Source note: This article includes information reported by KELO-LAND TV.
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