In a few years, tar spot has surfaced as a main concern in several key states. The corn disease stole upwards of 60 bu. per acre in severely infected fields in 2022, per Purdue University Extension.
As you pencil out your crop management plan for this year, assess your risk. Then, be proactive.
“The growers I talk to in counties where tar spot has been detected are making a planned application, or sometimes two applications of a fungicide,” says Ruhiyyih Dyrdahl-Young, BASF product manager of corn fungicides.
CONTROL BEYOND CHEMICALS
While several fungicides are on the market, you might be able to take a non-chemical approach, says Brian Hora, Continuum Ag adviser. He says tackling tar spot comes down to the macronutrient and micronutrient balance.
Ryan Gibbs, farmer and owner of Gibbsfield Ag in Dyersville, Iowa, believes good nutrient balance, including copper, can help.
“I had no tar spot in my non-GMO, no-till, cover crop corn last year,” he says. “My plant sap analysis found I have adequate or excessive copper in my plant, but I didn’t apply copper.”
Gibbs attributes his high levels of copper to no-till, applying manure, cover crops and composting extract biologicals.
“I think continued research will find tar spot is directly connected to a copper deficiency in soil which can be found in a plant sap analysis,” he says.
Beyond copper, Bill Verbeten, FMC technical service manager, says farmers should also focus on external factors that are driving the disease.
“If you’re looking at the whole suite of disease variables, it comes down to the weather — how it’s impacting the variability of tar spot and our ability to make a fungicide application,” he says.
Jenna Hoffman investigates the issues in Washington, D.C., that matter most to farmers.
