In the world of viticulture, growers frequently have to battle the hazards of nature. Fungi are among the most serious threats to a healthy harvest and a year's worth of work. In combating fungal infections, growers generally turn to a high-density chemical element: copper
Copper is a heavy metal found in nature, which plays an essential role in the process of plant photosynthesis. Its use in winemaking dates back to the end of the year 1800 as a way of primarily combating fungi and bacteria in the vineyard. Copper offers powerful protection against these microorganisms without damaging the plants or fruit.
However, copper – like other heavy metals – can have a toxic effect in the long term, because it tends to bioaccumulate. Bioaccumulation refers to the increased concentration of a chemical product in a living organism (a plant or animal) within a certain period of time compared to the concentration of said chemical product in the environment (Angelova et al., 2004).
In the vineyard, copper is applied externally to the plants, but when it washes off, it finds its way into the soil. According to a 2018 report by the French National Institute for Agricultural Research (INRA), the continued use of copper from year to year leads to an accumulation in the soil that can adversely affect the growth and development of most plants, microbial communities, and soil life. The risk depends on the rate of accumulation and the type of soil, because copper is a non-degradable metal. Copper has the second most deterrent effect on root development after herbicides.
Although it is one of the primary tools used in organic viticulture, copper has engendered a vigorous debate about the environmental problems it may cause. In Europe, this has led to a reduction in copper applications, now limited to 4 kg/hectare/year, and analyses are underway to determine if its use is sustainable.
Can copper be replaced?
Fungal infections pose a real risk, especially in Europe where many wine regions, including Champagne and Galicia, have the kind of soil composition and rainy weather that make vineyards particularly susceptible. Without the use of copper, the impact of fungal outbreaks like downy mildew would make the majority of vineyards completely inviable.
Various alternatives exist at this time, which are either biological in origin – plant extracts or microorganisms – or inorganic products. Many are still in the research phase, and the vast majority cannot substitute copper entirely, but could reduce its use.
Jeff Baccus, vineyard manager at Joseph Phelps Vineyards in Napa, California, explains how he has always limited the use of copper to small amounts during shoot emergence to control fungal pressure early on in the season
His concern about the accumulation of this heavy metal, however, has made him move away from copper treatments in favour of reintroducing livestock to the vineyard. He believes the first step in any effective strategy to protect against fungal pathogens is to minimize the risk of infection through key physical and cultural decisions, such as the choice of variety, clone, rootstock, row orientation, and vine training.
Forecasting models are seen as another strategy to reduce copper inputs by increasing the efficiency of treatment timing (La Torre et al., 2018).
In Europe, the new lines of research include the project COPPEREPLACE RDI, which brings together 13 French, Portuguese, and Spanish organizations in the wine sector – including the Familia Torres and Jean Leon wineries – to significantly reduce the use of copper in winegrowing. At the same time, the project seeks comprehensive and sustainable solutions in line with environmentally friendly production methods.
Copper alternatives are still very limited and do not meet the demands of the sector at this time, nor do they make it possible to completely forego the use of copper. However, this could provide growers with the opportunity to develop a holistic approach in the vineyard that promotes soil life and vineyard health by adopting sustainable options. Given how the excessive use of copper can have a negative impact on the soil, it is crucial that we continue the search for new solutions.
Angelova V., Ivanova, R., Delibaltova, V. and Ivanov, K. 2004. Bio-accumulation and distribution of heavy metals in fibre crops (flax, cotton and hemp). Industrial Crops and Products. 19: 197–205.
La Torre, A., Iovino, V., Caradonia, F. 2018. Copper in plant protection: current situation and prospects. Copper in plant protection: current situation and prospects. Phytopathologia Mediterranea. 57, 2: 201−236