Tackling tar spot: 2021 harvest pushes forward

WASHINGTON, Ind. — Harvest is well underway across Indiana, and some farmers are dealing with yield loss from tar spot.

Long periods of wet conditions created favorable conditions for tar spot.

According to Purdue University, infected corn plants display small, raised black and circular spots or fungal structures called stromata on healthy or dead tissue of leaves, stalks and husks.

“Tar spot started in the northern part of the state,” said Jordan Arndell, technical agronomist at DEKALB Asgrow in southern Indiana. “We’re seeing it progress further south.”

In untreated research plots, Arndell found tar spot July 31 — earlier than he expected he would. The plot was in Daviess County in southern Indiana.

“It looks like it’s going to be a disease that the entire state needs to be concerned with,” Arndell said. “Tillage practices and crop rotations will probably have some efficacy. But timely applications of Delaro have been our best line of defense so far against tar spot.”

Crunch The Numbers

Arndell also encouraged farmers to review data from planting, herbicide applications and fertility practices.

Apps such as Climate FieldView can give insight into yield outcomes.

“We can hone in on what works for our farm and our operation,” Arndell said. “What works for one farmer may not work best for his neighbor.

“There’s an incredible amount of information right there at our fingertips thanks to Climate, and if we’re not utilizing that to our fullest potential, I think we’re leaving something at the table. And it might be because we haven’t thought about how much value that information provides each individual operation.”

Looking to 2022, Arndell encouraged farmers to start thinking about their herbicide lineup, specifically for soybeans.

“They have found weeds that have resistance to dicamba, 2-4,D and Liberty when post-applied in Tennessee and Arkansas,” he said.

However, when dicamba is pre-applied, he’s seen efficacy in weed control.

“That tells me that using our dicamba as a residual is going to be huge for us,” he said. “If we’re using overlapping residuals and multiple modes of action, we can combat not only resistance, but problematic weeds going forward.”