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Adepidyn fungicide: Baseline sensitivity and cross resistance patterns in Alternaria alternata from almonds.

Gilberto Olaya: Syngenta Crop Protection

<div>Adepidyn® fungicide (pydiflumetofen) is the active ingredient of Miravis®, a new fungicide currently under development by Syngenta. Miravis® is a carboxamide fungicide and is the first member of a new chemical group among the succinate dehydrogenase inhibitor fungicides (SDHI, FRAC code 7), the N-methoxy-(phenyl-ethyl)-pyrazole-carboxamides. The baseline sensitivity for <em>Alternaria alternata</em> was established using 40 isolates identified to be wild-type, sensitive to other SDHI fungicides, and with no identified mutations conferring resistance to SDHI fungicides. All monoconidial isolates were obtained from <em>Alternaria</em> blight infected almond leaves from California. The Adepidyn® fungicide baseline sensitivity distributions (EC<sub>50</sub> values) of the <em>A. alternata</em> isolates ranged from 0.003 to 0.785, with a mean of 0.056 In another study, the <em>in vitro</em> sensitivity of 102 isolates was determined for Adepidyn® and Solatenol® fungicides, boscalid and fluopyram. This group of isolates contained wild-type isolates and isolates identified to have mutations conferring resistance to SDHI fungicides. The<em> i</em><em>n vitro</em> sensitivity revealed an incomplete cross resistance pattern between Adepidyn® and Solatenol® fungicides, boscalid, and fluopyram. Adepidyn® fungicide demonstrated the highest intrinsic activity among these fungicides and across all the isolates with or without mutations in the sdh subunits (SdhB-H277Y, SdhB-H277L, SdhC-H134R, SdhC-H135R, SdhD-D123E, SdhD-H133R/P/T, SdhB-H277Y+SdhC-H134R and H277Y+SdhD-H133R). Boscalid was the least active compound, and the activity of solatenol was similar to fluopyram.</div>