May 21, 2024

Seed selection important step in managing tar spot

An example of tar spot on a corn plant.

ALTOONA, Iowa — Genetic resistance to tar spot should be the No. 1 consideration when seeking to manage the disease, according to agronomists at Pioneer.

Picking the right seeds appears to have a greater impact on symptoms and yield loss than either cultural or chemical management practices.

“Fungicide won’t save a susceptible hybrid from tar spot,” said Matt Vandehaar, Pioneer field agronomist. “You can’t fungicide your way out of tar spot.”

Tar spot continues to be a growing concern to farmers across the Midwest. Tar spot can overwinter on infested corn residue, increasing crop infection risks.

In addition to picking the right seeds, other tools are available to fight tar spot:

• Applying foliar fungicides, sometimes twice a season.

• Managing residue may also decrease the risk of tar spot.

• Tilling fields to bury infected residue and increase the rate of decomposition may help reduce the amount of tar spot overwintering. But tillage will not reduce the risk of infection from locally dispersed inoculum.

If tar spot remains an issue in 2024, rotating crops may be the best course of action, according to Pioneer. Rotation can allow residue to decompose and reduce the primary inoculum.

Erica Quinlan

Erica Quinlan

Field Editor