Q: How can you manage tar spot in corn?
A: Tar spot is essentially an expression of oxidized manganese in the leaf.
Plants can absorb manganese from the soil, and then it moves to the leaf. But most plants are desperately short of manganese. The last thing they want is for that manganese to oxidize and become essentially unavailable to them. Manganese will oxidize in the plant leaf only under significant oxidative stress, and the significant sources of oxidative stress are applications of high salt fertilizers, particularly nitrate — nitrate is a very potent oxidizer — and high-heat environments.
So, when you have the combination of these two things, manganese can begin oxidizing inside the leaf, and we call it a disease and call it tar spot. But it’s really a function of manganese oxidation happening inside the leaf.
From John Kempf’s Eco Ag U session at the 2023 Acres U.S.A. conference. Learn more from John and many others at our 2024 conference: events.acresusa.com.
