ABSTRACT Wheat sharp eyespot (WSE) is a major fungal disease threatening wheat production in the Huang‐Huai‐Hai wheat region of China, and chemical seed dressing remains a widely applied strategy for its control. In this study, the mycelial growth rate method was employed to determine the sensitivity of 99 Rhizoctonia cerealis isolates to flutolanil collected from 16 cities in Henan Province in 2023. The biological characteristics of isolates exhibiting varying sensitivities to flutolanil were evaluated, alongside correlations in sensitivity between flutolanil and six additional fungicides, and the field efficacy of seed dressing treatments. The concentration for 50% inhibition of mycelial growth (EC 50 ) of flutolanil against the tested isolates ranged from 0.125 to 0.502 μg/mL, with an average of 0.252 μg/mL, presenting a unimodal sensitivity distribution. No significant difference in mean sensitivity was observed between cities across the province. At the baseline sensitive concentration, flutolanil reduced mycelial dry weight by 56.1%, sclerotial production by 39.0% and sclerotial germination by 13.7%. No significant virulence correlation was found between flutolanil and difenoconazole, fludioxonil, thifluzamide, tolclofos‐methyl or validamycin, whereas a positive correlation was detected with tebuconazole. Seed dressing with 20% flutolanil WP at 82.5 g a.i./100 kg seed achieved 38.2%–65.0% control efficacy against WSE at the jointing, filling and wintering stages. These findings provide a scientific basis for the rational use of flutolanil in WSE management and highlight the need for ongoing monitoring of R. cerealis sensitivity to this fungicide.
Zhou et al. (Fri,) studied this question.