Spraying Tasseled Corn

July 16, 2017

Recently, there have been some really tall sprayers on the road, and helicopters or airplanes flying low over the fields. Most likely these are related to applying a fungicide to corn late in the growing season.

We apply fungicides to all of our crops. They are critical to prevent or slow the spread of disease caused by fungi. Fungicides don’t kill their targets like insecticides and herbicides. Instead, they form a barrier to protect the plants from disease infection. It has been common to spray wheat and soybeans with a fungicide at least once per growing season for many years. However, spraying corn after tassel emergence has not been common on our farm simply because of the cost to apply the fungicide and the short duration of disease protection. Tasseled corn is often too tall to use a ground sprayer, and helicopters are very costly. Considering the cost to make the application with the short two week timeframe that the plant is actually protected, we concluded that it was a low return on investment opportunity.

In 2015, however, our thinking changed when a summer tropical storm passing over Central America before coming through our region brought with it Southern Rust, which is a fungus that attacks the leaves of the corn plant. This disease, like many, ultimately results in reduced yield by prematurely killing the plant. That year we hired a helicopter to spray half of a field. The results were astonishing and really opened our eyes to the economic returns a fungicide application can bring. We gained between 15 and 20 bushels per acre where we applied fungicide. In 2016 we tested fungicide on a larger area over several different corn hybrids. A smaller, but still positive, return on our investment was realized that year also.

This year, new fungicide technology that expands the protection window to 45 days is now available. This is a significant improvement and offers the opportunity to adjust the timing of applications. Also this year we had some corn grow short enough to allow us to spray it with our own ground sprayer. We added new attachments to our spray boom that applied fungicide both above and below the corn canopy. The change in placement improves leaf coverage and hopefully maximizes return on investment through improved effectiveness. We hired a custom applicator with a high clearance ground sprayer to apply fungicide on all of our remaining acres that were too tall for our sprayer. By using ground sprayers, we were able to design and implement extensive test plots that will allow us to evaluate the effect of application timing and placement against no application at all. We are optimistic that the results of our research this year will help us make solid data-based decisions on capital investments in the future.

Plant health is critical to maximizing yield in corn, especially when there is heavy disease pressure present. Fungicides have shown their ability to keep the plant healthy, and we believe that the introduction of fungicides offering longer residual control and investments in our equipment to allow ground application over tasseled corn will provide an economically viable practice for years to come.