Breaking the Mold: Fungicides in Wet or Dry Weather

Thursday, June 20, 2013
bayer fungicide treated corn field

Many growers breathed a sigh of relief when spring 2013 showed up and brought with it ample rainfall. After all, one of the most severe and widespread droughts in recent memory overtook most corn- and soybean-growing regions of the country in 2012. Any precipitation was good precipitation, as it would help replenish the depleted soil moisture so vital to ensuring seeds germinate after planting.


But the rain continued to fall. A number of regions saw a record-setting amount of rainfall in April. While it was helping the soil moisture, it also meant the wheels of tractors weren’t turning in many corn or soybean fields.


According to the U.S. Department of Agriculture, 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 5 percent of the corn crop had been planted.


The end of April is an important milestone for growers. Agronomic research suggests that as the amount of corn planted after May 1 across the Corn Belt increases, production decreases. The growing season is cut shorter, limiting the yield potential of full-season hybrids and forcing some 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. Few professions have so many vital variables — such as weather — beyond their control. As May 1 inched closer on growers’ calendars and clouds continued to settle in to weather forecasts, they started looking at contingency plans, which are never far from their minds.


Because late planting dates create a downward pressure on yields, growers are doing all they can within their power to get as much return per acre as possible. One way to accomplish that is through crop inputs. Herbicides manage weed pressure, eliminating competition for nutrients between crops and weeds. Insecticides stop and prevent pests from feeding on plants.


Because late-planted corn typically is more prone to disease infections, 2013 is an important year for growers to consider fungicides. While the number of growers who apply fungicides to corn has increased in recent years, it isn’t yet an assumed standard practice, as it is with herbicides.


Randy Myers, Ph.D., fungicide product manager for Bayer CropScience, explains why growers should consider fungicide applications.


"There are two principal reasons why late-planted corn is typically more affected by diseases," Myers explains. "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."


"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."


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 tries playing a trick on growers, and the cool, wet spring develops into another hot, dry summer, repeating a similar pattern faced by many growers in 1983? The common, but incorrect, assumption by many growers is that fungicides are beneficial only in wet conditions, when disease is more likely. These growers may assume that if it’s dry, they won’t get any value from fungicide applications.


"Common misconceptions 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 application of Stratego YLD in 2012, before they knew they would face dry weather conditions. The growers reported that fields treated with the fungicide yielded better than the untreated corn. In a year like 2012, an increase of just a few bushels per acre can lead to significant dividends.


In research trials during 2010-11, which had more consistent normal 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 just a few more bushels per acre, an application of Stratego YLD can pay for itself.


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