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POSTERS: Chemical control

Baseline sensitivity of Cercospora sojina isolates to adepidyn causing frog eye leaf spot on soybeans.
Gilberto Olaya - Syngenta Crop Protection. Kimberly Edlebeck- Syngenta Crop Protection, Rachel Linley- Syngenta Crop Protection, Heather Kelly- University of Tennessee

Frog eye leaf spot caused by Cercospora sojina is a soybean disease that can be controlled with foliar fungicides. Adepidyn® is the active ingredient of the fungicide Miravis® and is the first member of a new chemical group among the succinate dehydrogenase inhibitor fungicides (SDHI, FRAC Group 7), the N-methoxy-(phenyl-ethyl)-pyrazole-carboxamides. The common name for adepidyn is pydiflumetofen. Adepidyn has high binding properties to the complex II enzymes that provide a strong fungicidal potency combined with the control of a wide range of plant pathogen species. The sensitivity of 35 isolates of C. sojina to the fungicide adepidyn was determined using a mycelial inhibition growth assay. Isolates were obtained from symptomatic lesions from several soybean production areas in the USA. Sensitivity tests were conducted in vitro using V8 agar media amended with adepidyn. Mycelial growth inhibition was quantified using the following adepidyn concentrations: 0, 0.001, 0.01, 0.1, 1, 10 and 100 mg.ai/L. Baseline sensitivity distributions (ED50 values) of C. sojina isolates ranged from 0.0158 to 0.7405 mg.ai/L with a geometric mean of 0.1763 mg.ai/L and a range of 47X. Baseline sensitivity will be used in resistant monitoring studies focusing on early detection of resistant isolates.