Fungicide-Resistant Diseases Spreading
Soybean farmers have a new resistance challenge – fungicide-resistant diseases.
At the same time that many U.S. soybean farmers are battling herbicide-resistant weeds, now they have another issue for which their previous management methods may no longer work.
Carl Bradley, Ph.D., plant pathologist at the University of Kentucky, says soybean farmers and agriculture in general could be facing a big obstacle.
“If fungicide resistance becomes more widespread, we will lose an important tool in disease management,” he says.
As soybean prices have increased, so has the use of fungicides to increase yields and manage fungal diseases, such as anthracnose, Septoria brown spot, Cercospora leaf blight, frogeye leaf spot, pod and stem blight and soybean rust. 
In 2014, a study funded by the Mississippi Soybean Promotion Board (MSPB) allowed samples from over 630 soybean leaves from 73 counties to be sent to Jeff Standish, a former Mississippi State University graduate student in plant pathology, for laboratory for analysis. He found that frogeye leaf spot strains resistant to the strobilurin class of fungicides was present in at least one field in all 73 counties.
Before using a foliar fungicide, Bradley advises farmers to scout and determine the type of disease present to help determine which products to use.
Farmers can proactively implement best-management practices now to curtail fungicide resistance, including:
- Become aware of common diseases. For example, if farmers see frogeye leaf spot on their farm year after year, then management of that disease should become more of a priority. Integrating different practices for disease management will result in the highest level of disease control.
- Choose a resistant variety. Bradley says this is the most important decision a farmer can make in managing a disease.