Baseline and Temporal Changes in Sensitivity of <i>Zymoseptoria tritici</i> Isolates to Benzovindiflupyr in Oregon, U.S.A., and Cross-Sensitivity to Other SDHI Fungicides

Zymoseptoria tritici is the causal agent of Septoria blotch (STB), a disease wheat (Triticum aestivum) that results in significant yield loss worldwide. Z. tritici’s life cycle, reproductive system, effective population size, and gene flow put it at high likelihood developing fungicide resistance. Succinate dehydrogenase inhibitor (SDHI) fungicides (FRAC code 7) were not widely used to control STB Willamette Valley until 2016. Field isolates collected dates spanning introduction SDHI (2015 2017) screened for sensitivity four active ingredients: benzovindiflupyr, penthiopyrad, fluxapyroxad, fluindapyr. Fungicide changes determined by concentration which fungal growth decreased 50% (EC 50 ) values. The benzovindiflupyr EC values increased significantly, indicating reduction sensitivity, following adoption Oregon (P &lt; 0.0001). Additionally, cross-sensitivity among ingredients was also observed with moderate relationship between penthiopyrad = 0.0002) weak fluxapyroxad 0.0482). No change fluindapyr, has yet been labeled region. document decrease Valley. highlights notion careful consideration required manage resistance suggests within-group rotation insufficient management.