March 29, 2024

Disease continues to impact Indiana farmers

INDIANAPOLIS — Tar spot is a relatively new disease in Indiana, but it has the potential to cause major damage.

Corteva Agriscience provided a tar spot timeline to show the effects of the disease since 2016.

Tar Spot Timeline

• 2016 to 2017 — Minor economic impact.

• 2018 — Yield reductions of up to 50% for Midwest farmers.

• 2019 — Minor economic impact.

• 2020 — Economic impact isolated to irrigation and high rainfall areas.

• 2021 — Major economic impact.

• 2022 — Expansion westward.

During the first few years of its presence in the United States, it appeared that tar spot might remain a relatively minor cosmetic disease with little economic effect, according to Corteva.

However, in 2018 tar spot established itself as an economic concern for corn production in the Midwest.

Growers in areas severely impacted by tar spot anecdotally reported yield reductions of 30% to 50% compared to 2016 and 2017 yield levels.

Pathogen Facts

• Tar spot, caused by the fungal pathogen Phyllachora maydis, is a relatively new foliar disease of corn in the United States, first appearing in Illinois and Indiana in 2015 and subsequently spreading through much of the Corn Belt.

• Look for tar spot to develop during cool temperatures between 60 and 70 degrees, high relative humidity greater than 75%, frequent cloudy days and 7-plus hours of dew at night.

• Tar spot reduces yield by reducing the photosynthetic capacity of leaves and causing rapid premature leaf senescence.

Learn more about tar spot at https://tinyurl.com/46expmvw or https://tinyurl.com/8f5n6b3p.

Erica Quinlan

Erica Quinlan

Field Editor