Ag Notes

Pre-Season Tar Spot Checklist for Corn


Corn farmers in northern Illinois and across the corn belt have been dealing with a new disease. Todd Gleason has more on Tar Spot and what producers can do to mitigate its impact.

Tar spot is a relatively new disease of corn in the Midwest. It has been showing up on field corn in Iowa, Illinois, Michigan, Wisconsin, Indiana, Ohio, and Florida says University of Illinois Extension Plant Pathologist Nathan Kleczewski, "That's where it is found right now. But in terms of severity, where we have seen it the most and the pressure is the highest, if you would take the lower portion of Lake Michigan and draw a section around there, that is where we've had the greatest severity right now. That is where we've had the most pressure."

Kleczewski says this is because tar spot likes nighttime lows in the 70's and a lot of humidity. Here's a pre-season checklist for farmers in these areas concerned about the disease, "We do know that hybrids have different tolerance to this disease. They are all susceptible but some are less susceptible than others. And if you can get information from seedsman as to the tolerance rankings, go with something that is less susceptible if it fits your production needs."

Wisconsin Extension Plant Pathologist Damon Smith has a list of some corn hybrid tolerances to tar spot. That list can be found on the Badger Crop Doc website. The address is