Feverishly they search in the soil, on the leaves, and even in the genome. Researchers want to save organic viticulture. Because organic winegrowers have a big problem: a harmful fungus can destroy entire harvests. Only one pesticide is permitted in organic viticulture to combat this fungal disease: copper. But this is controversial because the heavy metal damages soil organisms. The EU therefore wants to ban the use of copper. Does this spell the end for organic viticulture? Or will science find an ecological remedy for downy mildew?
Winemaker Simone Adams works biodynamically, strengthening the defenses of her vines in a variety of ways. As a result, she only has to use a small amount of copper to combat downy mildew, far less than the 3 kg per year permitted for organic viticulture in Germany. However, she cannot do without it entirely, because otherwise her viticulture would no longer be economically viable due to crop failures.
Researchers in Germany and France are searching for strategies to replace copper. They are pursuing various approaches. On the one hand, they want to specifically influence the microbial colonization of grapevines and soils in order to strengthen the vines’ defenses. They are also investigating a mysterious network in the soil: mycorrhizal fungi form a symbiotic relationship with the roots of the grapevine and activate its defenses. The cultivation of fungus-resistant varieties, known as PIWIs, through marker-assisted selection is intended to make grapevines fundamentally immune to downy mildew.
A film by Angela Volkner.
Commissioned by ZDF/ARTE 2025.