Tennessee Extension plant pathologist tackles fungicide-resistant frogeye leaf spot, receives regional award

Frogeye leaf spot has always been a bane for soybean growers, but its recent resistance to fungicides has made it even more burdensome. So University of Tennessee Extension Plant Pathologist Heather Kelly has dedicated herself to learning more about the disease so that she can develop more effective control options and teach farmers how to use them. Her willingness to tackle the problem as a relatively new faculty member at UT caught the attention of her colleagues and earned her a Friends of Southern IPM Future Leader award, which she received on March 11 at the Southern Soybean Disease Working Group meeting in Pensacola, FL.

Originally from Orlando, Florida, Kelly joined the University of Tennessee in August 2012 as the Field Crops Plant Pathologist.

Heather Kelly

Heather Kelly and Henry Fadamiro

“Dr. Kelly regularly promotes integrated pest management practices within her extension publications and presentations by focusing on the basic “disease pyramid” to outline the factors required for disease epidemics to occur and how to use an integrated approach to manage these factors,” says Dr. Parwinder Grewel, head of the UT Entomology and Plant Pathology department.

Frogeye leaf spot typically affects the leaf of the soybean plant, although the fungus can also attack other parts of the plant as well. Diseased leaves have reduced photosynthetic rate and may pre-maturely defoliate, severely affecting yield. Better suited to warm, humid weather, the disease has been more prevalent in the Southeast than in the Central U.S., but it has moved to several states in the north central U.S. in recent years.

Although the disease has been in Tennessee for many years, farmers have been able to control it with fungicides until recently. In 2010, specialists discovered fungicide resistant populations in West Tennessee. Since then, fungicide-resistant frogeye leaf spot has been found in 11 different states and 172 counties. Kelly and other University plant pathologists are trying to gather as much data as they can to learn more about the pathogen.

“There’s still a lot to be understood about the disease,” Kelly says. “We’re investigating the disease cycle and how the pathogen interacts with different varieties, the environment and different practices, including interactions between cultural, chemical, and variety choice. We’re also using molecular tools to understand the pathogen and the host.”

Understanding the biology of the pathogen is crucial to developing a threshold for the disease. However, the complexity of the pathogen is making the research more challenging.

Once a threshold is in place, Kelly and her colleagues can work on a forecasting model to alert growers to scout their fields.

Kelly says that the support she has received from growers and Extension agents has contributed to the success of her research. To monitor for fungicide resistance, soybean sentinel plots are set up which are usually in a corner of a farmer’s field, which he/she doesn’t treat. Leaf samples are collected weekly by county agents and send to Kelly’s lab for analysis. Any spores recovered from frogeye leaf spot lesions on the samples are tested for fungicide resistance. The data she collects from sentinel plots as well as variety and fungicide trials will add to 10 years of data already collected by other UT specialists and bring them closer to understanding the disease.

In addition to her work on soybean and other field crops, Kelly collaborates with Tennessee Extension Entomologist and IPM Coordinator Scott Stewart and other researchers on pollinator health issues. A hobbyist beekeeper herself, Kelly is both personally and professionally interested in investigating the interaction of pesticides and pests of bees on colony health.

The opportunity to work on a variety of topics is one of the things that Kelly loves about her job. She has a joint research and extension position, so she is able to both research an issue and present her results directly to growers.

“The Extension appointment allows my research to truly be applied research,” she says. “I can directly relate my results to improve a farmer’s management practices. I not only enjoy educating farmers on best disease management practices, but also really enjoy teaching my graduate students. I feel I have great impact not only through the applied research that feeds into my extension program, but also through my students and the impact they will make in the world.”

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