Tar spot was found in Indiana on June 10 in Porter County, and since then four more counties have had the disease confirmed. Tar spot is still at a very low severity on the lower leaves, and mainly on corn planted in April. I have been receiving a lot of questions about what farmer should do and fungicide timing, so I have recorded a short video on some of our fungicide timing research here in Indiana. These first confirmations for tar spot this year are an indication to get out scout and keep and eye on your fields. As in previous years, we still have time to make an informed decision. In general, I still think it’s best to wait to at least tassel/silk (VT/R1) and would not spray before V10. Also check out some of the resources below to help make an informed decision on tar spot management on your farm.
Resources
https://cropprotectionnetwork.org/publications/fungicide-efficacy-for-control-of-corn-diseases
https://cropprotectionnetwork.org/web-books/tar-spot-of-corn