The use of copper in agriculture and its risks

Copper chemicals have been used for many years in agriculture to control fungal plant diseases. They usually consist of copper sulfates or copper oxychlorides, which interfere with the metabolism of fungi, effectively destroying them. They are effective across a broad spectrum, i.e. they affect many types of fungi indiscriminately.

Copper is also a micronutrient for plants and if taken in too large amounts it is toxic to plants. This is why copper-based treatments must be calibrated with the minimum effective against the disease, especially in a preventive manner.

Although these treatments are authorized by organic farming, they are not free of contraindications, so much so that the European Commission has included copper phytosanitary products among the substances to be replaced, financing the After-Cu study program . to find viable alternatives.

The fact that copper is authorized by the organic method may lead many to believe in good faith that it does not pose a risk to the environment: this is a myth that must be debunked. Certainly, the rules of organic farming guarantee greater ecological protection than traditional farming, in which products much worse than copper are authorized and used. However, care must be taken as even products of natural origin (the mineral in the case of copper) can have negative effects if abused.

Contents [Ocultar]

  • Presentation of the method

  • A little history

  • Effects and risks

  • Alternatives to using copper in agriculture


pressure method

A scientist spends days and nights of his life hunched over a book, to the point of becoming myopic. When someone asks him: “What have you studied all your life?” “, he answers:” I was looking for a cure for myopia.

This hyperbole from Masanobu Fukuoka, the father of natural agriculture, warns us against overreliance on science in the study of nature and agriculture. The risk for anyone who goes too far in a subject is to get lost in the details, to study them very carefully, but to miss the big picture. Thus, industrial agriculture has often found rather immediate solutions to problems, without taking certain factors into account, thus developing remedies that are not effective in the long term. In addition, it must always be borne in mind that, as in any economic sector, there are agricultural entrepreneurs who choose the path of immediate profit, at the expense of environmental repercussions and what will happen in the near future.

This premise is applicable to agriculture in general, today we are going to deepen one: the use of copper to fight against fungal diseases. This is a classic case where you’re often not fighting a disease, but blocking a symptom. The disease does not come from the plant, which is infested by a parasite, but it is the disease of an agricultural ecosystem that presents deficiencies. It may present deficiencies in biodiversity, in soil organic matter, in the ability of plants to absorb substances and in soil micro-organisms. The causes of this view are the most varied. The most important thing is to take care of the whole agricultural environment, only then the plant we want to grow will be healthy. The further one moves away from this point of view, the more short-sighted science becomes.

A little history

The first use of copper sulphates in agriculture dates back to 1761, when it was discovered that soaking seeds in a weak solution of copper sulphates inhibited fungal diseases transmitted by the seeds themselves. Since the beginning of the 19th century, the treatment of cereal grains with copper sulphates and their subsequent drying with lime has become common practice to prevent the formation of mold during storage.

The greatest advance in copper salts was undoubtedly in 1880 when the French scientist Millardet, while looking for a remedy in the vine against mildew, noticed by chance that a mixture of sulphates of copper, lime and water, made the grapes unappealing to passers-by. , made plants immune to disease. Thus was born the “Bordeaux mixture”, which takes its name from the French quarter of Bordeaux, and which remains today one of the most widely used fungicides in agriculture.

Effects and risks

The most effective use of these products is preventive Yes small dose . For example, if we are at the end of the winter period, it is very humid and last year there was an infestation in our orchard or vineyard, some product can be sprayed on the plants. In biodynamics, the use of copper-based products is allowed only for perennial crops up to a maximum of 3 kg of metallic copper per hectare per year, preferably using less than 500 gr./ha per treatment.

Spraying large quantities of product when the infestation has already started and during the growth period could do more harm than good in the long term. In this case, as we have seen, the symptom can be blocked, but the copper sulphates will eventually spread through the environment, settling on the ground. They will modify the ecosystem. So important for all our cultures. They can decrease the symbiosis between plant root systems and microorganisms, leading to poor absorption of nutrients. If the microorganisms are affected, the quality of the decomposition of the organic matter will also decrease and in general we will have weaker plants.

The risk is also to favor the development of resistance of pathogens to treatments, such as the excess of antibiotics in the human body.

The environmental pressure which is exerted on the ecosystem with the treatments will favor the adaptation of the micro-organisms which present favorable mutations to resist. This process is already underway: certain diseases are increasingly resistant to the use of copper sulphates, particularly in wine-growing environments, where the use of these products has been practiced for 130 years.

Reckless agricultural practices are reacting to increased pathogen resistance with the increased use of copper products, setting off a dangerous whirlwind of environmental degradation.

Regarding the development of resistance, another point was raised by Dr. Stefania Tegli, researcher at the Department of Food Production and Environmental Sciences at the University of Florence: Copper causes an alarming increase, in the microflora of agroecosystems, of the percentage of bacteria resistant to antibiotics, which end up constituting a sort of reservoir of antibiotic resistance genes. These genes are present in mobile elements of their genome, the plasmids, which can also be easily transmitted to pathogenic bacteria in humans and animals, making them in turn resistant to antibiotics and effectively nullifying their prophylactic and therapeutic action in medicine. human and veterinary. “.

Alternative to the use of copper in agriculture

For disease prevention, we must work by promoting the richness and stability of the ecosystem. From this point of view, biodynamic agriculture offers many useful tips. Specifically to reduce fungal diseases, soil quality is essential: mature soil and well drained This already helps a lot in prevention. This is achieved by avoiding tillage, the use of heavy vehicles and weeds, by not using pesticides and other synthetic products (including copper, at least in large quantities).

Proper fertilization also promotes the development of good sap, leading to strong, healthy plant tissues that are less vulnerable to disease development. On the contrary, an excess of nitrogen, for example, forces the growth of plants with less resistant tissues. From this point of view, biodynamic or natural fertilizations are generally more balanced for the plant (an article to find out more: the good nutrition of plants in biodynamics). Pruning should also be contained, but the foliage of the plant should be ventilated. Shade and humidity, on the other hand, will favor the development of diseases.

Finally, one last consideration that is often underestimated. If the plants get sick, it may not be the right crop for that location. We must respect the vocation of the territory and cultivate the varieties and crops that best adapt to the climate and the soil. I understand that the vine is profitable, but the pursuit of profit has already done a lot of harm to agriculture.

Personally, I think these means may be sufficient, but some natural fungicides recommended by biodynamic agriculture, such as bentotanium (powder of various rocks), propolis, horsetail decoction, lemon and grapefruit essential oils, Potassium baking soda should not suffice. Last but not least, the use of effective microorganisms, a combination of soil microbes that promote soil regeneration processes, nourishing the nutrient cycle, promoting the production of vitamins, hormones and enzymes.

In cultures where copper products are widely used, the doses and the number of treatments can be gradually reduced if all the good preventive practices we have seen are applied. In this way, it will be possible to reduce the number of treatments up to these two winter treatments, at low doses that may be necessary for certain types of crops of great economic importance in our lands.

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