When it comes to growing crops, hitting specific windows is important—for planting, spraying, fertilizing and, of course, harvest. That window approach also works when applying fungicides to corn. Those windows are the key times to maximize your yields.
“We really have three opportunities to apply fungicide to corn,” says Brad Ruden, Agtegra Agronomy Technical Services Manager. “The first is during planting, when fungicide is on the seed itself and possibly also in-furrow with a starter fertilizer. The second opportunity is when the crop is in the V5 to V6 range, which was several weeks ago. The third window is when the corn is starting to tassel—that’s our focus now.”
Benefits of Applying Fungicide at Tasseling
Ruden says that at tasseling, farmers should be looking to boost plant health and pollination to result in increased yields.
“In traditional corn areas, like the large production states called the “I” states, we see the largest yield response by applying fungicide at tasseling,” says Ruden. “We’re not only controlling disease during a time of much higher plant growth, we’re also boosting plant health by reducing the stress on the plant.”
The large yield responses are commonplace in areas of high disease pressure, but positive, economic yield responses also happen in northern growing regions. By protecting the corn plant at tasseling, Ruden says that it allows the corn to increase photosynthesis for more hours each day to maintain productive growth. Maximizing plant health also allows the corn to better handle stress from high temperatures.
“We want to keep that corn plant open and active, not rolling up each day,” Ruden says. “When the temperature hits 90 to or near 100 degrees, the corn plant shuts down, so if we can extend that window just a little bit, even in extreme environmental conditions, then we’ve done our job.”
Research conducted by Agtegra has shown that after applying fungicide, yield response can be as much as nearly seven additional bushels per acre. An additional seven bushels per acre can certainly add up at harvest.
Causes of Increased Disease Pressure
Ruden adds that some circumstances warrant higher consideration for applying fungicide.
“Corn is under higher stress when you’ve planted corn on corn or if the corn is irrigated,” he states. “Corn that is exposed to a higher moisture content in the canopy is more conducive to disease, especially where corn is planted on previous corn residue.”
Fungicides can protect corn from some of the most common diseases that hit corn foliage, according to Ruden. Gray leaf spot and common rust are the two primary offenders. Southern rust, a more damaging disease in corn, is less common, but does potentially threaten growers in southern South Dakota.
Aerial Application Preferred
How that fungicide is applied matters, too. Ruden says that most corn in Agtegra’s territory is in the pre-tasseling stage right now, so caution is required when applying fungicide.
“We want to be careful with applying fungicide on corn that’s in the late vegetative stages,” Ruden adds. “The ear is pushing through the plant, so waiting until tasseling for fungicide applications is needed to not hurt the development of the corn.”
While applying fungicide at some of those earlier windows can be done using a ground rig, Ruden recommends a different approach for applications that need to be done at this stage in the game.
“Because most corn is now too tall for ground application, aerial application is the ideal application method,” says Ruden. “Tassel timing application is also an opportunity to add crop nutrition at tasseling, possibly like a slow-release nitrogen. Visit with your Agtegra agronomist to determine which nutrition boost would be best for your fields.”
Fungicides and Severe Weather Events
Unfortunately, with summer rainfall and storms comes the possibility of hail damage or local area flooding.  “Fungicides can also help reduce stress on hail damaged corn or corn that has been temporarily flooded,” notes Ruden.  Provided the corn still has active growing leaf tissue, applying a fungicide can help reduce the negative stresses on the plant and help maintain the best opportunity for productivity.

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