Copper-based sprays  are used in conventional, organic and Biodynamic wine-growing, and for a wide range of other crops in agriculture in general such as fruit, hops, potatoes, vegetables and ornamental-plant production (IFOAM, May 2018, p.2.)

What is copper?: ‘Copper is a trace element and an essential micronutrient appearing in plant, animal and human tissue. Therefore, copper is used both in plant protection against bacterial and fungal diseases and as a foliar fertilizer [and] as a supplement in animal nutrition,’ (IFOAM, May 2018), p.1). 

How copper works: Copper binds to proteins in fungi and algae causing pathogen cells to leak and die. ‘Currently copper is approved as an active substance in plant protection product (PPP) for more than 50 different diseases in viticulture, horticulture, hops, market garden and arable crops. In particular, it is used in vineyards to control downy mildew (Plasmopara viticola, peronospora) on arable crops to protect potato against late blight (Phytophtora infestans), in apple orchards to prevent the spread of scab (Venturia inaequalis) but also in many other crops,’ (IFOAM, May 2018, p.1).

Why is copper allowed? Copper is allowed in organics and Biodynamics because it is deemed tradition and occurs naturally. In addition, copper-based sprays are contact sprays rather than sap-penetrating systemics. This means copper does not automatically end up in either the juice or the wine. It can however end up in the wine as residue from traces on the grape skins (for example from an application of copper in late summer, after which there was no rain to wash the copper of the skins). See Dr Richard Smart’s comment below for potential effects on wine.

How much copper is used in farming? ‘In the 1950s amounts of 20-30 kg/ha/year, exceptionally even 80 kg and more per hectare were applied for plant protection in Europe [crops in general as opposed to just vineyards]. Although copper formulations have been used for more than 100 years, there are no reported resistances which makes it a very important tool also in conventional and integrated pest management (IPM) farming systems,’ (IFOAM, May 2018, p.1).

Copper reduction: ‘The minimization of copper is a central topic in organic farming and is therefore also reflected in the development of organic regulations over time. In the first European organic regulation in 1991 a maximum of 8 kg per hectare and year was allowed. This was reduced in 2006 to 6 kg/ha/year. Under the current organic regulation (EC) No 889/20082 the 6 kg/ha/year was maintained,’ (IFOAM, May 2018, p.2). Additionally, a smoothing mechanism of 30 kg/ha for five years is currently in place,’ (IFOAM, May 2018, p.1). ‘A successful copper minimization strategy [means] farmers reduce copper in years with dry weather conditions. Only in years with very unfavourable weather conditions [is] the full [permitted] amount of copper allowed per ha per year used,’ (IFOAM, May 2018, p.3). Typically, organic and Biodynamic growers can use only around one fifth of the amount of copper permitted in conventional agriculture.

Soil toxicity: Copper build-up in the soil can be toxic and stunt vine growth, but can be neutralised by humus and lime (Hilary Wright: 2000, p.39).

Biodynamic and organic farmers are accused of having excess levels of copper in their soils. Analyses by Claude and Lydia Bourguignon of LAMS revealed that copper residues in Biodynamic vineyards do not stay in the top soil but descend to the sub-soil. ‘I don’t know why this is the case,’ Claude Bourguignon told me ‘only that it happens. Maybe the soil microbes are dragging it down.’ This observation stems from research conducted in the vineyards of Domaine Huet in Vouvray in the Loire, and Domaine Leflaive in Burgundy, amongst others.

Limits: Copper use is restricted by government regulations (eg. European Union, USDA, national agriculture ministries) and by Biodynamic and organic certification bodies.

Four ways to reduce Copper: Prof. Dr. Randolf Kauer of the Fachhochschule Wiesbaden, says: ‘the first way of reducing copper use is via bacteria, which are antagonistic to the downy mildew pathogen, Plasmopara viticola. Examples of such antagonistic organisms would be Pantoea agglomerans (formerly Erwinia herbicola) and others. These usually would be introduced to the vineyard via spraying. Successful application of such antagonistic organisms could reduce copper use by up to 50 per cent.

The second way of reducing copper use is by using phosphonic acid (phosphonates), which is a plant hardener. It can be used pre-flowering with no risk of residue appearing in the wine and soil; however when used after flowering it can leave a residue which is a problem under existing organic regulations.

The third way of reducing copper use is the best way, and involves adopting disease-resistant grape varieties (see PIWIs), such as Regent and Rondo for red wines, and Johanniter, Solaris and Saphira for white wines, all of which have been bred in Germany. These varieties need maybe one application of copper per year. All of these new varieties have non-vinifera parentage but are eligible for quality wine status under German and European law.’

A fourth way of reducing copper-based and other sprays is via systemically plant-induced resistance via the use of natural agents (plant-based sprays).

Levels used: Dr. Randolf Kauer (ibid) says ‘the average total level of [annual] copper use in German organic vineyards between 1997-2002 was 2.4kg/ha. On average, German organic winegrowers make 4 or 5 applications of copper per season, with each application containing between 500-800g/ha of copper.’

Copper & soil toxicity: Continued use of Bordeaux mixture can lead to accumulation of copper in the soil, causing reduced vine vigour, especially in acidic soils but this problem can be overcome by adding lime to the soil (Dr Richard Smart, 2015).

Replacement of copper: ‘Replacement of copper with another substance which has the same unique properties and which is equally or even better ecologically would need to have the following characteristics: 1) A significantly lower risk to health and the environment. 2) Be reliable and even with low application rates. 3) Have a high impact on many fungal and bacterial diseases. 4) Show no resistance in 100 years of practice. However, due to its unique properties copper is unlikely to be replaced with a new substance or range of substances that comply with all these criteria. See Andrivon et al,’ (IFOAM, May 2018, p3).

Copper & wine quality: Dr Richard Smart (2015) points out that copper sprayed on grapes within 14 days before harvest can produce browning, turbidity, and sulfide characters in the wine. It can also result in incomplete fermentations. (I am not aware of any wine-growers spraying copper-based sprays in the 14 days leading up to harvest.)

France: The national legal allowed application rate of copper is 6kg/ha/year with smoothing mechanisms (30 kh/ha/year) for organic agriculture. Private labels can be lower: e.g. Demeter allows 3kg/ha/year with smoothing. The amount of copper actually used in France as PPP in organic farming varies a lot from a region to another, from year to year. In 2013, the French Organic Research Institute (ITAB), the French Wine Institute and professional organisations have published a survey on 5 years of use of copper by organic winegrowers from 2008 to 2012. 2008 and 2012 have been years with bad weather conditions. Around 500 winegrowers answered. Producers use more than 4kg/ha/a in 4 years out of 5 in Champagne, 3 in Aquitaine, 2/5 in Burgundy and the least dependent is the Mediterranean area, Languedoc,’ (IFOAM, May 2018, p.6-7).

Germany: In the current national authorization of copper compounds in Germany the application of copper is restricted to 3 kg/ha/year (4 kg/ha/year for hops). The private associations of organic farming have always restricted copper applications to 3kg/ha/year (4 kg/ha/a for hops). Demeter in Germany does not permit copper application on Biodynamic annual crops (eg. onions), only on permanent crops (eg. vines).

However, for organic wine, in the last…difficult years 3 kg/ha/year has proved not to be sufficient for an effective control of fungal diseases in all regions.

From 2010 to 2017 36 research projects for copper minimisation were funded by the Federal Ministry of Food and Agriculture (BMEL) in the frame of the BOELN.

Progress was achieved in the reduction of the amount of copper per application in different crops. However, the overall duration of the vegetation period in the past years has considerably increased due to climate change. Thus, especially in vine growing a higher number of applications per year is needed so that the progress in reduction of the amount of copper per application was nearly completely counterbalanced by the higher number of applications.

In wine growing, in 2011 ca. 15 % of the area in investigation was treated with more than 2.5 kg. In 2012 and 2013 with more unfavorable weather conditions this area was more than doubled to about 30 %. I

In fruit growing, other minor diseases appeared (e.g. Marssonina coronaria) and the resistance of the scab resistant varieties 􏰀 an important part of the strategy – was broken. Until now, there is uncertainty regarding the availability of some alternative compounds that are also important parts of the strategy.

Austria: ‘Austrian Organic farming associations participate in the copper task force set up by the Austrian Agency for Health and Food Safety (AGES) in May 2014 with the common aim to minimize the use of copper. It consists of the different sector groups as well as of conventional and organic farming associations and industry representatives. It organizes a national event once a year in order to bring together different constituencies involved (conventional/organic farming associations, researchers, policy makers) and discuss the national copper minimization strategy,’ (IFOAM, May 2018, p.9-10).

‘In Austria, at national level a maximum amount of copper of 6 kg/ha/year is allowed in organic farming. The organic farming association Bio Austria sets considerably lower levels that are also crop- specific: 3 kg/ha/year in wine growing and fruit, 2 kg/ha/year in arable crops and 4 kg/ha/year for hops. The second relevant organic association Erde & Saat allows a maximum of 2 kg/ha/year with the exception of wine growing where it is 3 kg/ha/year,’ (IFOAM, May 2018, p.9-10).

Italy: ‘In Italy there is currently no maximum level for the amount of copper to use per ha and year in the national authorization (. However, there are limits for different products based on copper compounds. In organic farming, the limits of the Regulation (EC) 834/2007 are in force at national level. Several private organisations, especially the international organisations (Naturland, Demeter) and the Bioland association active in South Tyrol have lower limits (in general 3 kg ha and year). In the southern part of Italy the amount of copper compounds used by the growers is very low also in crops which traditionally use high amounts of copper like vineyards depending on the climate conditions in spring. In the typical northern regions (Piedmont, Friuli) famous for the excellent wines and important fruit industry, rainfall during the vegetation period is quite frequent and often severe. In these conditions 6 kg of copper per ha and year is often needed to protect efficiently the harvest from Plasmopara viticola and other disease,’ (IFOAM, May 2018, p.5).

See also: Bordeaux mixture. | Myco-Sin

Bibliography

Andrivon D., Bardin M., Bertrand C., Brun L., Daire X., Fabre F. ,Gary C., Montarry J., Nicot P., Reignault P., Tamm L.,SaviniI., 2017. Peut-on se passer du cuivre en protection des cultures biologiques? Synthèse du rapport d’expertise scientifique collective, INRA, 66p. https://inra-dam- front-resources-cdn.brainsonic.com/ressources/afile/423215-51d65-resource-expertise-cuivre-en-ab-synthese-francais.pdf

Dr Richard Smart (2015), Entry on copper in the Oxford Companion to Wine 4th edition ed. Jancis Robinson MW and Julia Harding MW (Oxford University Press, 2015), p95-6. 

Paulin Köpfer and Helga Willer, Paper prepared for BIOBACCHUS, International Organic Wine Conference, Frascati, Villa Aldobrandini, 5-6 May 2001.

IFOAM, Strategy for the minimisation of copper in organic farming in Europe (IFOAM EU Group), May 2018