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

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.