The Agronomists, Ep 77: Ken Currah and Greg Stopps on gibberella and tar spot management

Tar spot can reduce yield by 40 bu/ac

Host Lyndsey Smith is tackling gibberella and tar spot management in this episode of The Agronomists, with guests Ken Currah of BASF and Greg Stopps of Corteva.

This episode of The Agronomists is brought to you by ADAMA Canada, the Mind Your Farm Business podcast, and the Wheat School!

Don’t forget to apply for your CCA/CEU credits!  Catch a new episode of The Agronomists every Monday at 8 pm E.


  • Isolated pockets of really good territory in Ken Currah’s territory
  • Seeing a lot of dry crop in Greg Stopp’s territory. It’s quite dry. Seeing some leftover compaction issues from last year.
  • If the crop is variable, how do we time it?
  • Where things are extremely stressed, we should count our losses
  • You have to understand what you are targeting, too

CLIP 1: Corn School: Harvest quickly to limit losses to gibberella

  • Western bean cutworm is the first step in introducing the pathogen into the corn crop
  • The numbers look pretty high this year — especially in the pockets that are usually heavy. This year the drought makes the conditions favourable to seeing lots of egg masses
  • Why does western bean cutworm mean so much for the infection?
  • It starts with silk channel infection. The western bean cutworm spreads it
  • Use an integrated pest management (IPM) approach when it comes to scouting for the egg masses
  • The late silks getting attacked in a dry year — that’s really where the issues are
  • If we have no breeze going through the corn crop — that’s problematic, too
  • Don’t forget to lean on your local agronomist
  • Conditions in the canopy — are narrow rows increasing infection risk?

CLIP 2: Corn School: Inside the tar spot management toolbox

  • Tar spot, however, does not like drought
  • Ontario has not had the environment this year that is conducive to tar spot…yet
  • It is time to prioritize scouting for tar spot
  • Typically we see it mid-late August, where you wouldn’t quite expect to see corn turned as much yet
  • Are there genetic markers that can help us see the signs of tar spot? Not that is common knowledge yet, as it is a relatively newer disease. The way we will manage it is through genetics
  • Check out the full video for some interesting photos on tar spot side-by-side comparisons
  • Tar spot can move in later — are we ever looking at a second fungicide application? If so, when should we be timing it? In Ontario, we don’t really have that information, yet
  • You should not be doing two passes, unless your IPM program says so
  • Please pay attention to pre-harvest intervals when it comes to a late-season pass!
  • There’s tools to manage this…and it’s a whole IPM toolbox. Use that toolbox.

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