In chemistry we can find different forms of copper that act as a fungicide for agriculture. The most traditional and the most economical is copper sulphate, used as a fungicide, healing paste or algaecide for reservoirs and swamps.
Although still in use today, it was slowly replaced by other more efficient forms of coppersuch as copper oxychloride, copper hydroxide, copper chelate or organic forms such as copper gluconate.
The combination of sulfur and copper It is a very popular mixture since the sulfur acts effectively as a preventive against different types of fungi (such as powdery mildew), and in turn the copper acts by contact against a wide spectrum of fungi and even bacteria.
In this article, we tell you how to use copper sulphate as a fungicide and its main characteristics.
Characteristics of copper sulphate
Copper sulphate comes from the attack of copper rock (chalcanthite) with sulfuric acid, which gives the molecule CuSO4 (when it contains water, it becomes CuSO4 5H2O, the commercial formula).
Their characteristic blue colorstains any aqueous solution and coats trees and plants with a blue color, has made this formula an economical, effective and relatively long-lasting solution.
Its use is currently authorized in organic farming by the main producing and certifying countries (OMRI, NOP, CE 1009/2019, etc.).
- Trade name: copper sulphate pentahydrate
- Chemical formula: CuSO4 5H2O
- Copper richness: 25.0% w/w
- Apparent density: 2.3g/cm³
- Water solubility: 20.3 g/100 ml of water (temperature 20°C)
Dosage and use of copper sulphate in agriculture
Copper sulphate as an algaecide for tanks
The most economical water treatment is the application of copper sulphate directly into irrigation reservoirs. The dose of 2 g/m3 prevents the development of any species of algae, and if they are already developed, the dose to be applied is between 4 and 5 g/m3.
Copper sulphate as a fungicide in agriculture
Copper is used for control a large number of fungi They affect all kinds of plants. In general, most crops accept frequent applications of copper, both in foliar form and in fertigation, and it is an effective and inexpensive resource to delay or avoid the application of other phytosanitary active ingredients.
The dose of copper sulphate depends on the crop to be applied:
- Fruit, citrus and subtropical trees: 300-600 ml/hl in foliar application
- Horticultural crops: 150-300ml/hl
- olive grove: 300-600 ml/hl in foliar application (see uses of copper in olive groves)
- Vineyard: 300-600 ml/hl in foliar application
In foliar spraying, it will always be applied alone. Do not use on plants subject to stress (drought, flooding, shocks of cold or heat).
In liquid form, the maximum concentration it will have, once the rock or copper sulphate pole is solubilized, will be 6-6.5% w/w (w/w) copper.
fungus it controls
Copper sulphate as a fungicide works on virtually all types of fungi. Its effectiveness is much lower for neck or wood fungi (such as tinder), due to the difficulty of copper penetration inside conductive vessels, because it’s not systemic.
It is authorized and recommended against the following diseases:
- I repeat
- Other endophytic fungi
- More Effective Alternatives to Copper Sulfate
The discovery of new raw materials and field studies have made it possible to bring solutions to the market which, today, are quite numerous. more effective than copper sulphate as a fungicide.
When we talk about efficacy, we mention certain parameters such as the reduction of phytotoxicity, increased assimilation by foliar route, greater penetration by the root, better resistance to washing and lower risks of phytotoxicity due to excess copper. .
Some of these mixtures are copper hydroxide, copper oxychloride, copper EDTA chelate or organic forms that complex copper and increase its assimilation by the plant, such as copper lignosulfonate, copper gluconate or copper heptagluconate.
These solutions have also made it possible to reduce the consumption of the famous Bordeaux wine from the vineyard, solutions, a priori, less effective.
Both hydroxide and oxychloride provide a greater amount of copper (50-70%), the doses are therefore reduced and surfactants and surfactants are incorporated which increase their resistance to washing (a very important condition for copper applied in the spring, in periods of possible rain).
Instead, the organic agents protect the copper and increase its absorption capacity by the plant, both at leaf and root level.
This complexation also partially reduces the phytotoxic effects of copperbut care should always be taken with timing of application (eg do not apply with an open flower), crop conditions, combination with other products.
However, it should be remembered that most complexed coppers are derived from a base of copper sulphate.
Limitations on the use of copper
Copper has been in the sights of the authorities for several years. Being a product classified as organic, it has been used at higher doses and frequencies than recommended. However, it is not harmless to humans or animals.
The future limitation sets a maximum of 28 kilos of copper metal applied over a period of seven years. This translates to 4 kilos per hectare. Currently in Spain 6 kg per year are allowed.