Corn Fungicide Use - What Growers Must Know in 2025

By Blake Jackson

With the wet conditions, many growers are considering foliar fungicide applications on corn at the tasseling stage. In several regions, corn growth stages vary significantly from freshly planted to fully tasseled.

As such, it’s crucial to review fungicide labels carefully to ensure legal and effective use. Most fungicides are approved for application between the VT (Tassel) and R1 (Silking) stages.

The VT stage begins when the last tassel branch is visible, but before silking. This is a highly sensitive stage full leaf loss can result in nearly complete yield loss.

The R1 stage marks silking and is vital for nitrogen and phosphorus uptake, as well as successful pollination.

Some fungicides, like Miravis Neo, specify that adjuvants or additives should not be used beyond the V8 stage, although exceptions may be noted for fully tasseled corn. Recent research has linked improper adjuvant use near VT with “beer can” ear formation.

Given recent reports of Tar Spot, experts advise managing it similarly to gray leaf spot, applying fungicides when the majority of plants reach VT to R1. This avoids damaging younger plants and maximizes efficacy.

Also, be aware that certain products carry a 30-day pre-harvest interval for forage or grain. This could delay early harvests, making it important to plan accordingly.

In 2014, trials conducted with Dr. Collins demonstrated significant yield responses in six out of ten treatments some exceeding 11 bu/acre. The hybrid’s susceptibility to disease often influenced the outcome more than the fungicide brand.

To help decide on treatment, ask:

• Does the field have a history of disease, especially in low-lying areas?
• Is the field historically high yielding?
• What is the hybrid’s resistance to diseases like tar spot and gray leaf spot?
• Is the field corn-after-corn or rotated with other crops?
• How much disease is already present on leaves (under 5% to over 10%)?
• Is fertility high, average, or poor?

While no single answer applies to all fields, evaluating these factors can guide informed, field-specific fungicide decisions to preserve yield potential in a promising crop year.

Photo Credit: gettyimages-oticki