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POSTERS: Chemical control

Efficacy of fungicides containing mefentrifluconazole to manage Frogeye leaf spot of soybean
Leonardo Rocha - Southern Illinois University. Ahmad Fakhoury- Southern Illinois University, Madelyn Heinecke- Southern Illinois University, Jason Bond- Southern Illinois University

The use of foliar fungicides is critical in the successful management of Cercospora sojina, the causal agent of Frogeye leaf spot (FLS) in soybean. Most cultivars do not have resistance to this pathogen. In 2012, strobilurin resistant isolates of this pathogen were identified in Illinois and other states underscoring the need of fungicides with multiple modes of action. Mefentrifluconazole (BASF Corporation) is a newly developed DMI fungicide with activity against C. sojina and other pathogens of corn and soybean. The focus of this research was to evaluate the efficacy of mefentrifluconazole and other fungicides to manage FLS and protect soybean yield. Field trials were established in 2017 and 2018 to evaluate strobilurins and mixes containing strobilurin, triazole and succinate dehydrogenase inhibitor (SDHI) fungicides. The research sites were naturally infested with strobilurin resistant isolates. Fungicide treatments were applied at the soybean growth stages R3, R5 or R3 followed by R5. Assessments were foliar disease severity, stem and pod quality, seed quality and soybean yield. The treatment containing azoxystrobin and difenoconazole (Quadris Top SBX) and the treatment containing mefentrifluconazole, pyraclostrobin and fluxapyroxad (Revytek) significantly reduced disease severity up to 70 days after application. Soybean yield in Revytek treatments applied at R3, R5 and R3 & R5 were higher than all other treatments and were 10.6%, 11.8% and 16.8% higher than the yield in non-treated plots. This research will provide growers with information to better manage FLS.