Keeping Corn Fields Healthy: Fungicide Use and Weather

breaking the mold
Early season fungicide applications can help corn growers maximize yields,
no matter the weather.

Many growers breathed a sigh of relief when spring 2013 showed up and brought ample rainfall. The previous year, one of the most severe and widespread droughts in recent memory overtook most corn-growing regions of the country. After facing that challenge, the showers were a welcome change.

But the rain continued to fall, and some regions received a record-setting amount in April, meaning the wheels of tractors weren’t turning in many cornfields.

Coping with difficult weather

According to the USDA, nearly one-third of the country’s corn crop is typically planted by the end of April. In 2012, growers were well ahead of average with almost half of the corn crop in. However, by the end of April 2013, just five percent of the corn crop had been planted.

late planted corn is more prone to disease infections

Corn planted after April 30 significantly reduces production. The growing season is cut shorter, limiting the yield potential of full-season hybrids and forcing growers to shift to shorter-season hybrids with lower yield potential. 

Growers, however, are resilient and resourceful by nature. They couldn’t do their jobs otherwise, with so many vital variables beyond their control. In 2013, as May inched closer and the rains continued, they started looking at contingency plans.

Making the most of late planting

Because late planting dates create downward pressure on yields, growers are doing all they can to get as much return per acre as possible. For example, late-planted corn is more prone to disease infections, so 2013 is an important year to consider fungicides. While the number of corn growers who apply fungicides has increased in recent years, it isn’t yet a standard practice.


“There are two principal reasons why late-planted corn is typically more affected by diseases,” explains Randy Myers, Ph.D., fungicide product manager for Crop Science. “First, disease inoculum loads are higher when the late-planted corn plants are small and more vulnerable to infections. The high inoculum load is because soil temperatures are markedly warmer in late-planted fields, which speeds fungal development. And this year there is an abundance of moisture which caused late corn planting in the first place.

Growers reported that fields treated with the early fungicide application yielded better than the untreated corn
“The second reason,” Myers continues, “is because late-planted corn is more vulnerable to infections. The temperatures are warmer, causing plants to grow quickly. When plants grow quickly, their natural protective barriers are thinner and more easily compromised.”

How fungicide can make a difference

common misperceptions still exist when it comes to fungicides To best manage disease infection, Myers recommends that growers make an early season fungicide application as well as the more conventional at-tassel application.

“Applying a fungicide such as Stratego YLD early in the season stops initial infections, protecting leaf tissue and promoting healthy stalks,” he says. “Applying a fungicide at tassel helps shield the leaf canopy, protecting the photosynthetic surface area needed for grain fill.”

But what if the weather does not cooperate, and the cool, wet spring develops into a hot, dry summer, like in 1983? The common assumption is that fungicides are beneficial only in wet conditions. But that simply isn’t true.

Keeping yields strong, rain or shine

“Common misperceptions still exist when it comes to fungicides,” Myers says. “Growers should no longer assume that fungicide applications pay off in wet weather only.”

In fact, Myers talked with a number of growers who made an early season application of Stratego® YLD fungicide in 2012, before they knew they would face dry weather. Growers reported that fields treated with the early fungicide application yielded better than the untreated corn—an increase of a few bushels per acre that created significant dividends.

In research trials during 2010-11, which had more consistent weather, corn that received just one application of Stratego YLD at the V5 growth phase yielded 6.8 bu/A more than untreated corn. With returns like that, an application of Stratego YLD can pay for itself.

Works Cited

Weekly Weather and Crop Bulletin, U.S. Department of Agriculture

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