Baseline sensitivity of Fusarium graminearum from wheat, corn, dry bean and soybean to pydiflumetofen in Michigan, USA

Abstract

Fusarium graminearum is perhaps best known for causing head blight in wheat and ear and stalk rot in corn. However, F. graminearum can also cause seedling diseases and root rot on many field crops including wheat, corn, soybean, and dry bean. In 2019, a new Succinate Dehydrogenase Inhibitor (SDHI) fungicide, pydiflumetofen (Syngenta, Switzerland), was registered for management of Fusarium Head Blight of wheat and corn ear rot. Here, we determined the sensitivity of isolates of F. graminearum from wheat, corn, soybean and dry bean from Michigan to this new active ingredient. In vitro sensitivity of 94 isolates was assessed with a poison plate mycelial growth assay, and a subset with 21 isolates was also tested with a spore germination assay. The effective concentration that reduced growth or germination by 50% (EC50) was determined for each isolate. Mycelial growth EC50 values ranged from 0.008 to 0.263 μg/mL, with a mean of 0.060 μg/mL. EC50 values for spore germination assays ranged from 0.167 to 0.538 μg/mL, with a mean of 0.321 μg/mL. This study demonstrates both mycelial growth and spore germination are inhibited by this new chemistry in vitro. This data also establishes baseline sensitivity values of Michigan populations of F. graminearum before widespread application of this chemistry on commercial fields.