Supplemental data for: Determining effective management strategies for Stemphylium leaf blight of onion: Early infection trials

<p>Stemphylium leaf blight (SLB) of onion caused by Stemphylium vesicarium (Wallr.) E.G. Simmons is the most common foliar disease of onion in Ontario. The objectives of this research were to develop and evaluate disease forecasting models to reduce fungicide applications, detect infection of onion early in the growing season, and assess mutations associated with resistance to succinate dehydrogenase inhibitor (SDHI) fungicides in S. vesicarium. Modified forecasting models based on weather data or conidia counts did not reduce SLB severity. Infection of onion was detected in the field as early as the flag leaf stage and penflufen seed treatment did not reduce early season infection of onion. Six mutations associated with SDHI resistance were detected in S. vesicarium isolates collected in the Holland Marsh from 2021-2024. More research is needed to develop an effective forecasting model and assess mutations for reduction of efficacy for all registered SDHI fungicides.</p><p>This research included disease forecasting trials, fungicide resistance trials and early infection trials. This dataset includes the data for the early infection trials. Please see the Related Dataset metadata field for links to the datasets for the disease forecasting trials and fungicide resistance trials.</p>