Viewpoint: ‘A very curious form of self-sabotage’ — Organic industry rejects crop biotechnology solutions for environmental damage caused by widespread copper sulfate use

Application of copper to grape leaves. Credit: Stella Photography via Alamy
Application of copper to grape leaves. Credit: Stella Photography via Alamy
Last February, the National Agency for Food, Environmental and Occupational Health and Safety (Anses) published a “mapping” on the uses of copper. Passed under the radar of the national press, this report is in great danger of ending up in the depths of a drawer because of the not very politically correct nature of its conclusions.

Particularly rich in information, thanks to the elements provided by the Regulated Products Information Systems Department (SSIPR), which is the managing body of the Top database (Traceability and Process Optimization) within ANSES, ” the mapping of the uses of copper-based plant protection products published by the agency provides for the first time figures which clarify the considerable use of copper – around 1,900 tons per year on average for the last ten years – in the main agricultural productions. These cupric solutions are mainly used against apple scab, vine and tomato mildew, but also to fight against peach leaf curl, potato mildew or fruit bacteriosis (peach, plum, hulled, for example).

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Copper galore

The vine remains by far the agricultural sector most affected by the use of copper. Used since 1885, Bordeaux mixture, a solution based on copper sulphate mixed with lime which owes its name to the place of residence of its inventor, the botanist Alexis Millardet, has hardly known any modification since its beginnings.

“Since then, copper has been a major element in crop protection methods against various diseases,” notes the report by way of introduction, which recalls that in organic farming, “copper is applied to almost all surfaces in vine of all the wine-growing areas.”

With on average quantities added per hectare and per campaign two to three times higher in organic farming than in conventional agriculture, which also uses this active ingredient in its treatments.

As far as arable crops are concerned, copper is particularly used on potatoes, since 75% of the surfaces in organic farming are concerned, compared to only 0.1% in conventional agriculture, while in the cultivation of organic fruits and vegetables. [Peach crops] hold the absolute record with 100% of the areas concerned, followed by tomatoes and melon, with respectively 90 and 73% of the areas, and always with the application of two to three times more treatments than in conventional agriculture.

It is therefore easy to imagine the effect that the desired acceleration in the number of hectares converted to organic farming will have on tonnages. Thus, for the potato, the report estimates that a mere 13% increase in area would lead to an increase of more than 800% in the amount of copper dumped on the fields! A shame, when we read the note of November 28, 2018 cited in the report, which emanated from the Ministry of Agriculture: “The transition to more economical uses of copper and the use of substitution methods is necessary given the risks and potential impacts of excessive use of copper on the environment and health.”

The risks of copper

These risks are known and have already been widely documented, as evidenced by a collective scientific expertise from Inrae published in 2018, which recalls that several EU countries – including Denmark and the Netherlands – have already banned its use due to “negative environmental effects of copper, in particular on soil organisms and crop auxiliaries.”

According to a CNRS study published in 2021 on soil pollution, the amount of copper present in oysters from the Nantes estuary has doubled in thirty years.

“Excess concentrations of copper have recognized phytotoxic effects on the growth and development of most plants, manifesting themselves in particular by chlorosis and a reduction in the total biomass,” specifies INRAE, which indicates that certain crops, in especially legumes, vines, hops or cereals, are particularly affected. Finally, the experts point out that “the deleterious effects of excess copper on soil microbial communities, as well as its toxicity for certain components of soil fauna such as springtails, seem well established.”

So many reasons that doom copper to be a “candidate substance for substitution,” that is to say that the 57 copper solutions with [certification] today are supposed to no longer be authorized in the not so distant future! The question will indeed arise from 2025, the approval of copper having been renewed in 2018 for a period of seven years. Until then, however, farmers will still be allowed to dump up to 28 kilos per hectare and up to a maximum of 4 kilos per year. A practice that can hardly be described as “sustainable,” since these solutions are not biodegradable.

Indeed, as the Inrae report establishes, “the repeated application of copper-based pesticides is the main source of copper pollution in agricultural soils, and causes a sometimes massive accumulation of this element in the surface horizons.” Thus, in Europe, the almost uninterrupted application of Bordeaux mixture has increased the copper content of wine-growing soils considerably, and even worryingly, “up to values ​​that can reach 200, or even 500 mg/kg (compared to 3 to 100 mg/kg in natural soils).” This explains why we already find copper levels in certain vine-growing areas, making subsequent crops complicated, as Laurent Cassy, ​​operator of a vineyard in Morizès (Gironde) [southwest France] testifies: “On one of my plots, I had about 4,000 m2 where nothing was growing. [After asking experienced people] he realized that this location was that of “an old basin where we made Bordeaux mixture, and which sometimes overflowed” as he told it on Franceinfo. [Analysis] then confirmed that the soil contained copper “in significant proportions, enough to be harmful to the plants that grow there.” [Since planting the seed, it] “grows two to five centimeters, and then nothing.”

And that’s not all. According to a CNRS study published in 2021 on soil pollution, the amount of copper present in oysters from the Nantes estuary has doubled in thirty years. “However, this trace element, essential for life, is an extremely powerful antiseptic in high doses and becomes toxic for living beings,” notes the study, which considers it plausible that this copper comes from the Bordeaux mixture used by conventional winegrowers. and biological to treat the vine in the region.

Finally, the study by Public Health France carried out in July 2021 on “the impregnation of the French population by copper” quantified the levels of copper in the population. And if research into the determinants of exposure has shown that smoking status influences urinary copper concentrations in adults – smokers being more impregnated than non-smokers – in children, it is the more frequent consumption of vegetables from organic farming which is associated with an increase in urinary copper concentrations.

Organic at an impasse

However, as far as organic farming is concerned, to date there is no known “non-chemical” alternative that is really effective, which promises a very delicate situation in the future for the organic production concerned.

“Most of the projects for the development of alternatives to copper concern organic farming, which uses copper in significant quantities without the availability of alternative active substances to copper authorized in organic farming and presenting the same effectiveness,” worries ANSES. Admittedly, the use of biocontrol products makes it possible to reduce the quantities of copper, but the authors acknowledge that “their limited effectiveness would not make it possible to completely replace copper.”

With regard to changes in agricultural practices “in a logic of redesigning cropping systems,” the experts recommend “technical support for farmers” and “the provision of decision-making tools” as well as “economic incentives” due to increased workload, such as chipping leaves for apple scab and walnut anthracosis. But again, these are only very partial solutions.

In the end, the work of the experts highlights above all the fact that, for organic farming, “there do not seem to exist at present any alternatives to copper which could be considered feasible.” A ban on copper in 2025 would therefore put entire sectors of organic farming in great difficulty, going against the various European and national plans to promote this type of farming.

NBTs to the rescue of organic

How then to get out of this impasse? Clearly, in the absence of other solutions, varietal resistance, which “occupies an important place in the design of low-copper systems,” remains the most promising avenue.

We remember BASF’s Fortuna project proposing a potato resistant to mildew. A ban on copper in 2025 would put entire sectors of organic farming in great difficulty, running counter to European and national plans to promote this type of farming.

This new tuber was designed from a European potato known to give quality fries, to which we had added two genes from another potato more resistant to mildew. Lacking societal acceptability, this project had to be abandoned in the 2010s. “The continuation of investments cannot be justified due to the uncertainty of the regulatory environment and the threats of destruction on the ground,” explained the German giant.

Under the pressure of deadlines as short as 2025, it would now be essential to relaunch, and even accelerate, the search for new varieties resistant to both scab and mildew. However, although there are several public research projects in this field, mainly developed in China and the United States, a complicated legal context and uncertainties about future European legislation concerning NBTs contribute to strongly curb the enthusiasm of breeders. For its part, Inrae does not even mention varietal improvement among the alternative solutions to copper detailed in its collective expertise of 2018…

To make matters worse, the organic sector, which could greatly benefit from modern techniques of varietal improvement, continues to mobilize to ban their use. A very curious form of self-sabotage…

[Editor’s Note: This article was originally published in French and has been translated and edited for clarity.]

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