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Distribution, genetic diversity, and impact of fungicide resistant Cercospora sojina, the cause of frogeye leaf spot in soybean, in Tennessee
H. KELLY (1), K. Lamour (2), W. J. Jordan (1), A. Cochran (1). (1) University of Tennessee, Jackson, TN, U.S.A.; (2) University of Tennessee, Knoxville, TN, U.S.A.

Frogeye leaf spot (FLS) of soybean, caused by <i>Cercospora sojina </i>K. Hara, is a common foliar disease in the southern USA and parts of the midwestern and northern USA.  Yield losses ranging from 20-60% are not uncommon in years where weather conditions are favorable for fungal growth and cultivars lack genetic resistance. Management strategies to control FLS include planting resistant varieties and applying foliar fungicides. In 2010, the first <i>C. sojina </i>isolate with resistance to quinone outside inhibitor (QoI) fungicides was reported in Tennessee. Since that time <i>C. sojina </i>isolates with resistance to QoI fungicides have been confirmed in 10 states, across 67 counties/parishes in the US. <i>C. sojina </i>field studies have been conducted across Tennessee to investigate genetic diversity, disease severity, response to fungicides, and impact on yield. The results of these studies and the impact of QoI resistant <i>C. sojina </i>isolates will be discussed.

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