Variables To Consider For Fungicide Timing

Soil conditions. Your hybrid. Moisture. Your chosen product. So many factors impact fungicide timing.

“There’s no one-size-fits-all scenario for fungicide application,” said Federated agronomy sales manager Kevin Carlson. “There are different timings for different products and different diseases. But that’s what we’re here for!”

Carlson detailed some general rules of thumb for your fungicide application.

“For white mold, it's when flowering starts, so it’s generally around the 4th of July in our region,” he said. “Soybeans trigger to start flowering after the summer solstice on June 21. When the nights start to shorten, soybeans trigger that they need to start flowering. A week to ten days after that, you start seeing flowers. That’s when we spray.”

White mold is a fungus, so it likes warmer, wetter conditions. It’ll infect the flower as it starts to senesce. That’s why we time application for flowering.  “The challenge here is that soybeans will flower for an entire month,” Carlson said. “And that makes getting coverage for an entire month with a single application difficult. That’s why white mold is so hard to manage.”

For corn, it’s all about growing degree units.

Although fungicides can be applied as early as V10 or as late as R2, we see best results at tassel. “There’s a long history of data that proves the best time to maximize ROI on fungicide is at tassel,” Carlson said. “Applying fungicide at tassel protects the corn at its reproductive stage.”

Predicting tassel is where growing degree units (GDU) come into play. “We’re at between 650 and 700 GDUs now, depending on when we planted,” Carlson said. “Most seed companies have a GDU for flower ot tassel set at 1200 to 1250. That means we have about 500 to go, which puts us at pretty normal timing, from July 15 to July 20. We’re right on target.”

There are a number of GDU calculators available online that can help you determine your ideal application date, or call your Federated Agronomist for assistance.