Fungicide resistance is an issue in grain crops production that is beginning to cause problems for growers trying to manage foliar diseases of grain crops. The biggest challenge has been managing frogeye leaf spot of soybean, due development of resistance to strobilurin fungicides in the causal pathogen, Cercospora sojina.

To help get the word out about fungicide resistance, Dr. Bradley has been an important national leader in partnering with key programs and developing extension products that can be used by extension professionals, farmers, crop consultants, and the ag industry, in general. Most recently, he was the initial plant pathology partner in the “Take Action” program. The Take Action program is sponsored mostly by Soybean Checkoff dollars with many partners in the industry with the purpose of educating people about the risk of resistance in crop protection chemicals (https://iwilltakeaction.com/). Two events that attracted lots of interest that Dr. Bradley was involved with was a panel at the Commodity Classic Annual Meeting in Anaheim, CA in March 2018 that had over 8,000 attendees, and a live TV show, “Rural America Live” that was broadcast during “primetime” on RFD TV Network in June 2018. RFD TV averages over 132,000 viewers during primetime.

Fungicide resistance education products developed through Take Action that are available on-line (https://iwilltakeaction.com/) include:

• Fungicide Classification Chart
• Fungicide Efficacy Fact Sheet
• Common Soybean Disease Infographic
• Plant Disease Triangle Infographic
• How Does Fungicide Resistance Develop?
• Best Management Practices for Fungicide Resistance
• Know Your Disease Risk in Soybeans – What’s Your Score?

In addition, Dr. Bradley coordinates the annual list of counties/parishes in the U.S. that have strobilurin-resistant strains of the frogeye leaf spot of soybean pathogen. His lab was the first to report on strobilurin fungicide-resistant strains of the frogeye leaf spot pathogen in 2010 (Kentucky, Illinois, and Tennessee), and his lab continues to receive samples from across the U.S. to help document new areas that have strobilurin fungicide-resistant strains of this pathogen. In addition to those outputs listed above, a peer-reviewed journal article is currently in-press that reports on all of the observations of strobilurin fungicide resistant strains of the frogeye leaf spot pathogen in the U.S. (Bradley et al., 2018), which has been in a total of 240 counties/parishes from a total of 14 states. Funding for the work comes from the United Soybean Board.

Reference:

Zhang, G., Allen, T. W.,……..Bradley, C. A. 2018. Widespread occurrence of quinone outside inhibitor fungicide-resistant isolates of Cercospora sojina, causal agent of frogeye leaf spot of soybean, in the United States. Plant Health Progress (in press).