While fungicides can be effective in treating yield-reducing fungal diseases in corn and soybean crops, a Purdue Extension plant pathologist says farmers should scout fields to determine whether fungicide application is necessary.
In so doing, crop producers can identify fields that are at-risk and ultimately only apply fungicides when necessary, said Kiersten Wise. Doing so can increase profits and save money by preventing unnecessary applications.
"The first step in the decision process for a fungicide application is determining if disease is a problem and then determining what disease you have," Wise said. "Fungicides aren’t going to manage every disease."
Her research indicates that the greatest chance of economic return from a fungicide application in corn or soybeans is when fungicides are applied in response to presence of a disease or if there is a high risk of disease.
Many important diseases of field crops, like sudden death syndrome of soybean, cannot be managed effectively with fungicides; instead, specialists recommend planting varieties with good resistance to the syndrome.
Wise said there are many other sources of plant abnormalities, such as nutrient deficiencies, pesticide damage and environmental damage, that can mimic crop diseases, which makes scouting and sampling very important.
Farmers can get a fast and accurate diagnosis for a crop problem by submitting plant samples to Purdue’s Plant and Pest Diagnostic Laboratory. Visit http://www.ppdl.purdue.edu/PPDL/ for more information.
Growers also can call their county Purdue Extension office for help (888-EXT-INFO). Web tools and Extension publications also are available to help with diagnosis.
Wise cautions against diagnosing plant problems completely based on pictures.
"Sometimes it helps to look at the whole plant and have people trained in diagnosis determine what’s wrong," she said.
If during the season growers find and confirm a disease problem in a field, a fungicide application may help prevent further spread of the disease, depending on the particular disease and the crop’s growth stage at the onset of disease onset, Wise said.