Supplemental data for: Determining effective management strategies for Stemphylium leaf blight of onion: Disease forecasting trial

The objectives of this research were to detect infection of onions early in the growing season, develop and evaluate disease forecasting models to reduce fungicide applications and assess mutations associated with succinate dehydrogenase inhibitor (SDHI) resistance in S. vesicarium.

Modified forecasting models based on either weather data or conidia counts did not reduce SLB severity. Infection of onions was detected in the field as early as the flag leaf stage but penflufen seed treatment did not reduce early season infection of onions. Six mutations associated with SDHI resistance were detected in S. vesicarium isolates collected in the Holland Marsh from 2021-2024.