2023 Tar Spot

Sep 05, 2023

Tar spot has been a popular topic during this growing season in our trade territory. We can find Tar Spot in about every field, but northeast of Knoxville has seen the most this season. I have been keeping an eye on an area this season that has been a hotspot and the disease progression is very fast. Areas with high infection are shutting plants down quickly, especially with the dry weather we’ve experienced the past three weeks. Observations I’m seeing are areas that had more rainfall during June have higher instances of infection. Once we get to the Melcher Dallas area or move to our southern territory in Appanoose county, we see much less Tar Spot. I attribute this to the lower rainfall in these areas. Fungicide applications are preventative with Tar Spot so a good idea for next year will be to target areas that have more moisture during June.

Below is a picture of corn leaves from Knoxville area fields that I have been keeping an eye on. They all have different management practices, but overall fields sprayed with fungicide are going to be in better shape than untreated fields. Tar Spot is relatively easy to control with fungicide, but the disease moves so fast that if it goes uncontrolled it can cover plants and shut them down in just a few weeks. No fungicide applications have given us 100% control, but the sprayed fields easily have 70-80% less lesions than untreated applications. Our recommendation for fungicide application at SFG is still to treat the fields with high yield potential or with hybrids we know respond positively to fungicide. Scouting and monitoring moisture in fields is going to help us with making decisions on Tar Spot but once you see the disease the damage is already done. Contact your agronomist about Tar Spot to help determine what your plan needs to be for 2024.