On today's episode: Why did we see so much southern rust in the 2025 corn crop? We talk about this foliar disease, where it comes from, the impact it had on the crop and what farmers can do to better manage it going forward. We'll also explore some fascinating agriscience happening that will give farmers better protection against crop diseases like southern rust in the future.

To guide us through all of this, we're talking to Mark Jeschke, agronomy manager supporting the Pioneer brand at Corteva Agriscience. Mark has been with the company for 18 years and is currently based in Johnston, Iowa. He also farms with his family in Northern Illinois. Also joining the show is Pioneer field agronomist Carl Joern. Carl saw a lot of southern rust this past growing season in his area of northwest Indiana and northeast Illinois. He works directly with farmers in his role as a field agronomist and focuses on making sure they can make the most profit from Pioneer products.

“ Southern rust can be scary, especially if you don't have experience with it and when you have environmental conditions that stack the deck in its favor. There are fields across the Midwest this year that got sprayed with a fungicide and in three weeks that corn crop looked dead. And folks are trying to consider how to manage for a disease and how you invest in a crop that doesn't look like it's invested back in your operation…Like anything in farming, how you manage your operation has an impact on how pathogens proliferate and how different weed species grow or don't grow on your farm.” - Carl Joern

And while this year was bad and was a learning experience for many people, it’s not a new disease. Mark Jeschke remembers starting to see it in 2016 and says it has shown up earlier and earlier in the last couple of years, creating a bigger management concern. This threat can become a huge issue, taking away yield and potential revenue at a time when margins are thin. But could some of the modern gene editing tools that we’ve talked about in previous episodes of this podcast potentially help reduce this risk? Jeschke definitely sees this as a possibility.

“ What our scientists have done is take multiple disease resistance genes and stack those all together. So you're delivering multiple genes for resistance to different diseases all at once…It's a concept that can be expanded going forward that can add more resistance genes to it…So it can be iterated and improved upon over the years. So that's very exciting.” - Mark Jeschke

A few takeaways from today's episode:

1. A better understanding of southern rust: where it comes from, what causes it to spread and some management tips
2. For as sophisticated as modern farming is, there are curveballs every year. Sometimes the timing doesn’t work out to address them reactively. That’s why the work of agriscience innovation is never finished to create better solutions
3. Multi-disease resistance or the disease super locus is really an exciting development. This is a very real and timely example of where gene editing technology could address a problem that farmers have no way of knowing in advance if they need to prioritize.

Agriscience Explained is brought to you by Corteva Agriscience and hosted by Tim Hammerich. This show is produced by Clint Pilcher, Rayda Krell and Ann Leonard. Jaime Hammerich and Grant Bolton edit these podcasts, and the music was composed by Dmitri Volkov. Subscribe for more Agriscience Explained: From Science to Solutions.