An agronomist suggests tar spot is a corn disease that is tough to figure out.
Tony Lenz with Stine Seed Company says since it was discovered in 2015, tar spot has continued to spread.
“Originally we talked about it had to be high humidity, it had to be a certain temperature. But I think what we’re learning now this year again is about this wetting of the leaf, wetting (and) drying of these plants.”
Tar spot has already been confirmed in several Iowa counties and Lenz tells Brownfield it doesn’t take much moisture for the pathogen to emerge.