Sulphur is heavily relied upon in organically farmed vineyards to control powdery mildew. Sometimes, high application frequencies and high dosages are required to achieve control during high disease-pressure periods. This could lead to Fito-toxicity symptoms in the vine and high irritability for the spray operator. In this study, the efficacy of silicate, in combination with lower sulphur dosages, was evaluated as an alternative powdery mildew control mix.
Project layout
The trial was conducted in two organically managed vineyards in the Abruzzo region over three seasons. Both sites are in hilly areas and are highly susceptible to powdery mildew. The first site was a 36-year-old Trebbiano vineyard, where the trial was conducted during 2022 and 2024. The second site was a five-year-old Pecorino vineyard, where the trial was conducted during 2023 and 2024. Treatments included:
- Sulphur
- Calcium silicate + sulphur
- Silicon oxide + iron + sulphur
- Equisetum arvense + sulphur
- Untreated control
Measurements included disease incidence and severity, crop yield and quality.
Results
- In the old vineyard site, the calcium silicate + sulphur treatment significantly reduced disease severity in the 2022 and 2024 seasons compared to other treatments.
- The same results were achieved in the younger vineyard site in the 2024 season.
- In both sites, the calcium silicate + sulphur treatment showed lower disease incidence and severity than the conventional sulphur treatments.
- During 2024, significantly higher yields were measured with the calcium silicate + sulphur treatment at the old vineyard site than other treatments.
Significance of the study
Depending on the costs and availability of silicate products, it could be a valuable addition to the powdery mildew control “arsenal” for organic producers. The good results obtained regarding foliar symptom suppression from these silicate products also shows promise in lowering powdery mildew infection source the following season. Finding the right silicate product and application mix with sulphur in South Africa warrants further local investigation.
Reference:
Calzarano, F., Pagnani, G., Seghetti, L., D’Agostino, V., & Di Marco, S. (2024). First Results of Management of Powdery Mildew in Grapevine Using Sulphur, Silicate and Equisetum arvense Formulations. Agronomy, 14(12), 2930. https://doi.org/10.3390/agronomy14122930