As part of the “Zéro black-rot” program, the French Institute of Viticulture (IFV) is investigating how effective biocontrol is in the fight against black rot disease in vineyards. This disease is becoming a serious problem because grapevine varieties are being developed that are resistant to blight and powdery mildew, but are sensitive to black rot. Therefore, it has become a priority to find effective biocontrol products, and IFV has been leading this program since 2021.
The program was started by testing different active substances in the laboratory and in the greenhouse, in order to identify those with the greatest potential for successful biocontrol. After these preliminary tests, field experiments were conducted on microplots that were under heavy pressure from black rot disease. The results of these tests made it possible to divide the products into three categories: effective solutions, products that deserve further research and those that were eliminated due to insufficient efficiency.
When it comes to biocontrol, the combination of sulfur and potassium phosphonate proved to be the most effective combination. This combination achieved an efficiency of 78% in the protection of bunches, which is almost equal to the efficiency of metiram (82%) and the combination of sulfur and copper (81%).
Sulfur was applied in amounts of 3 to 8 kilograms, depending on the stage of vine growth, together with a full dose of phosphonate. Another product, a combination of sulfur and Armicarb (potassium bicarbonate), showed a slightly lower efficiency of 69% on clusters. However, when these products were used individually, their effectiveness declined significantly. Phosphonates alone had 50% efficiency, sulfur 40%, while Armicarb only had 30%.
Biocontrol or not, black rot is creeping up
Potassium hydrogen carbonate (Vitisan) is in the category of products that deserve further research. The one in question showed promising results at the beginning of the season, with an efficiency of 55% on the leaves, but only 19% on the bunches.
Sweet orange essential oil had similar results, with 40% efficacy on leaves and 18% on clusters. However, it should be noted that these results were very uneven. Carpet (sodium hydrogen carbonate) was 36% effective on leaves and only 9% on clusters. Although these products have produced interesting results in laboratory and greenhouse conditions, further research is needed to confirm their utility in the field.
The third group includes products that did not show efficacy on leaves or bunches, with results similar to untreated samples. Among them are Romeo (a defense stimulator based on yeast cell walls), Sonata (Bacillus pumilus) and Redeli (disodium-phosphonate). Although the last two gave good results in laboratory conditions, they were not successful in field tests.
It is important to note that although some biocontrol products have shown efficacy against black rot, they are not yet approved for use in the fight against this disease. This means that winegrowers cannot currently use these products to control black rot.
However, IFV research may lead to expanded permitted uses for these products in the future. The next steps of the “Zéro black-rot” program include the validation of risk prediction models and the construction of strategies with optimized doses. Those doses will be tested on larger plots in cooperation with partner winegrowers.
Source: Vitisphere
Source: boljazemlja.com
