Help weather (pun intended) adverse weather conditions in corn

3 Key Weather Stressors in Corn

Fungal disease and wet weather. They seem to go together like Bonnie and Clyde – the combination might not lead to good things, but you typically don’t have one without the other.

Fungal disease in corn needs wet weather to take hold and, if untreated, negatively affects your yields. That’s when you apply a fungicide, usually at tassel, to control the disease. It’s the only time you ever need to consider applying a fungicide.

Or is it?

Independent studies increasingly show that a fungicide application can actually help corn weather (pun intended) adverse weather conditions, such as hail damage. Corn treated with a fungicide often better withstands winds that might down corn in a neighboring field. In fact, fungicides can even help your field when the weather is drier than normal.

1. Hail Damage

hail damage


The first line of defense against to limit the impact of hail damage is to apply fungicide before any hail event occurs, Randy Myers, Ph.D., Bayer Product Development Manager, explained.

“A fungicide application before you have hail means the plant’s physiological reactions are already triggered before the leaves are damaged,” Myers said. “It means there are no latent infections that can take advantage of the weakened plants, since they have already been cleaned up by the fungicidal performance.”

If a fungicide application didn’t happen prior to the hail event, you can still get some benefit from a fungicide application, regardless of the plant stage. Myers explained this is because a fungicide such as Stratego® YLD benefits the plant in two ways

  1. The plant’s hail-damaged vascular structures slow the flow of water and nutrients. This means photosynthetically active surface areas are not able to capture as much energy for the plants’ consumption. The injured plant is less able to respond to the infections. The fungicide helps fight fungal pathogens that readily feast on this weak tissue caused by hail damage.
  2. The strobilurin component of Stratego YLD encourages the formation of callus tissue, closing the wounds caused by hail and eliminating a pathogen’s easy access to the vulnerable interior of the leaves. This barrier preserves plant productivity, enhancing recovery.


2. Wind Damage

wind damage


A relatively new benefit of fungicide application is how it can help your corn withstand straight-line winds that might flatten your neighbor’s field.

As Alison Robertson, Department of Plant Pathology and Microbiology, Iowa State University, states in “Thoughts on Spraying Downed Corn with a Fungicide.”

Flattened corn may provide a better microclimate for disease development because leaves are closer to inoculum source, less wind movement through canopy, higher humidity and longer periods of leaf wetness that may favor infection.

Robertson goes on to explain, though, that, “Fungicide coverage of flattened corn will be more sporadic because penetration through this altered canopy will not be as thorough.”

Randy Myers, PH.D.“The best thing you can do to manage flattened corn is to do everything you can to prevent such damage,”

- Randy Myers, PH.D.

A few questions clearly linger about the effectiveness of a fungicide application to downed corn, and several university studies are underway to evaluate its effectiveness.

In the meantime, Myers provided a recommendation similar to that he made for fungicides and hail-damaged corn.

“The best thing you can do to manage flattened corn is to do everything you can to reduce such damage,” Myers said. “An early season fungicide application (V4 to V7) is shown to improve stalk strength and reduce the risk of lodging. If you have a stronger stalk, the plant is less likely to fall victim to strong winds and bend over or snap off.”


3. Dry Weather

dry weather


It might seem counterintuitive to apply a fungicide when it’s dry. After all, most diseases need moisture to thrive, so they certainly won’t thrive during a dry year. A common 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, there is no value in a fungicide application.

“Common misperceptions still exist when it comes to fungicides,” Myers says. “Fungicides trigger beneficial physiological reactions in the plant, even with dry weather and in the absence of visible disease symptoms.”

One of the physiological reactions is the fact that fungicides help a corn plant improve its water efficiency when rainfall seems to be scarce.

In fact, Myers talked with a number of growers who made an early application of Stratego® YLD in 2012, the most recent widespread drought, before they knew that dry weather conditions would take hold. The growers reported that fields receiving the fungicide yielded better than untreated corn.

Application Methods

Clearly, prevention is the best approach when it comes to mitigating the effects of serious weather events.
Growers can consider two approaches to preventive fungicide applications; 1) the more common at-tassel aerial application; 2) an early season application between V4 and V7, usually tankmixed with a planned herbicide application.

  • At-Tassel
    An at-tassel application of Stratego YLD delivers improved stalk strength with reduced risk of lodging and green snap, as well as preventive and curative activity against gray leaf spot, northern corn leaf blight, and/or southern rust. Replicated research trials indicate that Stratego YLD applied at VT increases yield by 11.8 bu/A on average. If corn is $4/bu, that means you have the potential to make about $22/A more.

  • Early Season
    Despite the history of fungicide application between the VT and R2 growth stages, the practice of early season fungicide application - between the V4 and V7 stages of corn – is becoming more common.

    During these stages, corn plants go through critical changes that will affect the yield potential of the field. Having to secure all of their own nutrients and plant resources for the first time, plants are susceptible to environmental stresses and diseases. Applying Stratego® YLD at this stage is not only convenient, but it also offers early season disease control and more complete plant coverage.

When applied at a rate of 2 oz/A, growers saw an average yield increase of 6.8 bu/A. This means that even with $4 corn you have the potential to see a $19.15 return on investment.

Master the weather, read more

  • When Weather Delays Planting
  • Wet or Dry: Weed Management
  • Financial Returns of Early Season Application

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