Project leaders: Tim Duckert and Quinten Sackett, NCRS
Tar spot has the potential to be a serious issue for corn producers when field conditions are right for disease spread. Research on tar spot resistant varieties and fungicide products has shown some disease control, but often not full control of the pathogen. The Corn Marketing Program of Michigan (CMPM) has funded research on tar spot since 2019. This research project takes an integrative approach to tar spot control involving chemical and cultural management practices.
To gain a better understanding of tar spot disease control, two hybrid corn varieties (DK 51-40[susceptible] and DK 53-27[tolerant]) were tested against the fungicide Veltyma at different application methods and timings (picture 1). The fungicide application methods included a spray boom and using the 360 Undercover from 360 Yield Center. The hypothesis is that the 360 Undercover technology will provide more effective spray coverage to the ears and leaves in between rows, and therefore provide greater tar spot control. The fungicide treatment was applied twice, once at 5-feet tall and again at the R3 growth stage. The second application was delayed from a planned VT/R1 application due to low disease pressure.
Disease pressure in central Michigan has been low in 2023 and tar spot was not detected in Clinton County (where the trials are located) until August 4, 2023. Prolonged drought conditions through May and June restricted disease development, however consistent leaf wetness through September could lead to increased disease pressure before harvest.
Visual evaluation for tar spot disease will be regularly conducted up until harvest at the research plots (picture 2). The project team has utilized drone imagery (NDVI/NDRE) to identify spots of tar spot infection and will continue to do so through the season. Harvest data, weather data, and leaf wetness data will all be collected at the end of the season.
Next steps: This is the second year for this research project. Upon completion, data from both years will be analyzed for trends and the results will be published in the CMPM annual research report, which will be released in early 2024.
Picture 1: tar spot research plot at the North Central Research Station in Clinton County, MI.
Picture 2: tar spot infection on untreated control leaf within a tar spot research plot.