Be proactive in preventing tar spot

WESTFIELD, Ind. — The first annual Tar Spot Summit was held Nov. 28-29 in Westfield.

Mike Kavanaugh, director of product development at AgReliant Genetics, shared details with AgriNews.

Q: How did the Tar Spot Summit go?

A: The Tar Spot Summit was a major success. The goal was to bring together masterminds in the corn disease world and create a think tank to discuss tar spot. It was 24 hours of major brainstorming and good discussion.

Q: What is tar spot?

A: Tar spot is a fungus that has blown in from southern countries. We first saw it in a big way in 2017, and its footprint has increased ever since. We found that it overwinters in crop residue. It incubates in cooler, humid conditions.

Q: What does it look like?

A: It’s a very aggressive disease that can cover the whole leaf surface with spots that literally look like tar. When it covers the entire leaf, with the right environmental conditions on susceptible hybrids, it can choke the leaf from sunlight and photosynthesis. When that happens, it greatly affects grain fill. Yield loss can be very significant. Anywhere from five to 70 bushels, depending on the severity.

Q: What is the outlook for tar spot in the Midwest next year?

A: As we look at history, it started around 2017 around the Michigan, northern Indiana, northern Illinois and Wisconsin area around Lake Michigan. Every year, it spreads further south in Indiana. It’s spread as far west as Iowa. 2018 and 2021 were really bad years; the environment was conducive to tar spot. For 2023, it’s unknown. All we know is that it’s been found in many states in the Midwest. If we have a cool, wet year with lots of humidity at the right times, it can be very detrimental if not managed for.

Q: What advice would you give farmers concerning tar spot?

A: Midwest farmers should make sure they’re being proactive and using prevention measures, such as choosing hybrids with good tolerance to tar spot. Make sure that’s one of the ingredients that make up the total recipe in their portfolio. Secondly, crop rotation can be utilized as a management strategy. Thirdly, if they’re concerned about it, build in fungicides into their program next year. Those are the main takeaways.