Tar spot is in mid-Missouri, prompting farmers to consider applying fungicides for management.

The University of Missouri confirmed tar spot in Howard County late last week. Until then, the fungal disease made it to nearby northeast Kansas, east-central Iowa and northern Indiana.

However, MU plant pathologist Mandy Bish was fielding calls and emails about the appearance of tar spot from crop scouts across the northern region of Missouri.

WHERE NEXT? A map of the Midwest shows where tar spot has been confirmed. There is a likelihood it could spread. University researchers and farmers are watching. Photo by MU Integrated Pest Managment

Missouri’s first proven tar spot report is in a V10/V11 corn field that had tar spot in 2023. The plan for this field is a fungicide application at VT/R1.

Fungicide applications are an important tool for managing tar spot during seasons with high outbreak, according to Bish. And while waiting is hard for famers, she says, current research proves this timeframe offers the best control option.

What to expect with tar spot

Here are the key points regarding fungicide applications for managing tar spot:

Related:How to manage tar spot in corn

Bish says many products evaluated in research trials offer yield protection to some extent during seasons with high tar spot severity. These include Veltyma, Revytek and Delaro Complete. They offer the most consistent reduction in disease severity and yield protection.

Be prepared for fungicide application

First scout. Second, wait.  

In 2024, scouting for tar spot is crucial, according to Bish, especially in regions where the pathogen is known to survive winter. Monitoring fields allows timely preparation for fungicide applications as corn approaches reproductive stages.

"Remember that we want to protect the ear leaf and ear development," she says." A fungicide application is going to last 14 to 21 days in general. Fungicides applied prior to tasseling have not shown consistent protection of the ear and subsequently of yield."

If you spray too early, you are likely to need a second application, Bish notes. The most consistent data is an application between VT/R1 and R3 when conditions favor progression of the disease.

"And remember that diseases are not like weeds,” she adds. “The pathogen is going to require favorable weather conditions to continue growing and spreading.”

Reach out to MU or your local agronomist to confirm tar spot in corn fields. Once confirmed, determine the need for a fungicide treatment. The Crop Protection Network publishes a corn fungicide efficacy guide that is updated annually and includes efficacy information on tar spot.