**4.1 Copper as fungicide**

First uses of fungicide reach back 400 years ago where simple water solutions (salts) were frequently used for cereal seed treatments. Not earlier than at the beginning of 20th Century more complex organic chemical solutions were introduced (Bordeaux and Burgundy mixture etc.). Nowadays a considerable number of phytochemical companies offer numerous and different classes of fungicides, where copper fungicides according to their antifungal and antibacterial effects play an important role. The efficiency of copper fungicides, particularly aggressive in moist media, is caused by denaturation of protein structures (secondary and tertiary) of fungi and bacteria, and consequently the interruption of their functions. Copper forms compounds in the oxidation states of +1 (cuprous) and +2 (cupric), but trivalent copper in aqueous solution splits rapidly.

Classification of copper fungicide according to chemical structure:


#### **4.1.1 Copper sulphate (cupric sulphate)**

Copper(II) sulphate is a very versatile chemical compound with a wide use in industry but also in horticulture where it exists in a various forms that differs in degree of hydration. Cupric sulphate is the most frequently used form of Cu in pesticides against many diseases listed in Table 3. It is produced industrially by treating copper metal or its oxides with sulfuric acid, or with placing of copper in a solution of nitric or sulfuric acids as well as in water. The chemical form copper sulphate pentahydrate (CuSO4 x 5H2O), a fungicide, mixed with hydrate lime (Ca(OH)2), is called Bordeaux mixture or with sodium carbonate (Na2(CO)3) Burgundy mixture. Both Cu solutions are used more than 200 years yet, especially in fungi disease control in horticulture (vineyards, orchards etc.).

Bordeaux mixture is produced by dissolving copper sulphate and hydrated lime in water, mostly in a concentration of 1 %; in relation 1:1:100 means 1 kg of copper sulphate and 1 kg of hydrated lime is dissolved in 100 litres of water. Copper sulphate contains approx. 25 %

Copper plays an important role not only in pathogen controlling but also in soil fertilization, animal nutrition etc. Excessively long copper use in plant protection but also in terms of fertilisation in modern agriculture lead to copper accumulation in soils, where copper surplus is considered if the soils contain more than two parts per million available copper, bearing in mind the physiological and biochemical needs of the plants. On the other hand the same soil conditions in context of copper deficiency can also affect nutritional statuses of

First uses of fungicide reach back 400 years ago where simple water solutions (salts) were frequently used for cereal seed treatments. Not earlier than at the beginning of 20th Century more complex organic chemical solutions were introduced (Bordeaux and Burgundy mixture etc.). Nowadays a considerable number of phytochemical companies offer numerous and different classes of fungicides, where copper fungicides according to their antifungal and antibacterial effects play an important role. The efficiency of copper fungicides, particularly aggressive in moist media, is caused by denaturation of protein structures (secondary and tertiary) of fungi and bacteria, and consequently the interruption of their functions. Copper forms compounds in the oxidation states of +1 (cuprous) and +2

Copper(II) sulphate is a very versatile chemical compound with a wide use in industry but also in horticulture where it exists in a various forms that differs in degree of hydration. Cupric sulphate is the most frequently used form of Cu in pesticides against many diseases listed in Table 3. It is produced industrially by treating copper metal or its oxides with sulfuric acid, or with placing of copper in a solution of nitric or sulfuric acids as well as in water. The chemical form copper sulphate pentahydrate (CuSO4 x 5H2O), a fungicide, mixed with hydrate lime (Ca(OH)2), is called Bordeaux mixture or with sodium carbonate (Na2(CO)3) Burgundy mixture. Both Cu solutions are used more than 200 years yet,

Bordeaux mixture is produced by dissolving copper sulphate and hydrated lime in water, mostly in a concentration of 1 %; in relation 1:1:100 means 1 kg of copper sulphate and 1 kg of hydrated lime is dissolved in 100 litres of water. Copper sulphate contains approx. 25 %

especially in fungi disease control in horticulture (vineyards, orchards etc.).

animals and consequently their life expectancy.



**4.1.1 Copper sulphate (cupric sulphate)** 

(cupric), but trivalent copper in aqueous solution splits rapidly. Classification of copper fungicide according to chemical structure:


**4.1 Copper as fungicide** 


copper as metal, therefore the content of Cu in 1 % Bordeaux mixture varies between 0 and 25 %. On the other hand 1 % Burgundy mixture is made by dissolving 1 kg of copper sulphate in 50 litres of water and separately 125 kg washing soda (or 0.475 kg soda ash) in 50 litres of water. After that the soda solution has to be slowly added to the copper sulphate solution with stirring. Both mixtures have been effective in controlling most of the fungi diseases of plants, applied in a time span of 10 to 20 days, depending on fungi species, plant, weather conditions, age and phenological stage of plants etc. According to the manner of Cu use it is important that first spraying is done before the diseases is expected and continued at regular intervals throughout the susceptible period. The protective coating of Cu mixtures prevents spores germination and consequently their damages caused by penetration through tissues of unprotected parts of plants. An effective spraying scheme has to ensure permanent copper coating over susceptible plant parts, what demands accuracy of the timing of the spraying, especially at precipitation (> 30 mm) and at intensive fruit growing (fruit enlargement).


Copper in Horticulture 267

Leaf curl (*Taphrina deformans*) Rust (*Puccinia pruni-spinosae*)

Shot hole (*Clasterosporium carpophilum*)

Shot hole (*Clasterosporium carpophilum*)

Scab ( America) (*Cladosporium effusum*) Thread blight (*Corticium koleroga*)

Bacterial spot (*Xanthomonas pruni*) Black rot (*Dibotryon morbosum*) Blossom wilt (*Sclerotinia laxa*) Brown rot (*Sclerotinia fructigena*) Rust (*Puccinia pruni-spinosae*)

Shot hole (*Clasterosporium carpophilum*) Watery rot (Pocket plums) (*Taphrina pruni*)

Cane spot (Anthracnose) (*Elsinoe veneta*) Cane wilt (*Leptosphaeria coniothyrium*) Spur blight (*Didymella applanata*)

Angular leaf spot (*Mycosphaerella angulata*)

Wilt (*Pseudomonas prunicola*)

"Coitre" (*Coniothyrium diplodiella*)

Anthracnose (*Elsinoe ampelina*) Crown gall (*Bacterium tumefaciens*) Bitter rot (*Melanconium fuligineum*) Black rot (*Guignardia bidwellii*) Downy mildew (*Plasmopara viticola*)

Leaf spot (*Isariopsis fuckelli*)

Powdery mildew (*Uncinula necator*) Totbrenner (*Pseudopeziza tracheiphila*)

**Strawberry** Leaf spot (*Mycosphaerella fragariae*)

Leaf spot (Leaf speck) (*Mycosphaerella sentina*)

Bacterial canker (*Pseudomonas mors-prunorum*)

Brown spot (*Alternaria passiflorae*) Grease spot (*Pseudomonas passiflorae*)

Leaf curl (*Taphrina deformans*) Rust (*Puccinia pruni-spinosae*)

Bitter rot (*Glomerella cingulata*) Firebiiglit (*Erwinia amylovora*)

Scab (*Venturia pirina*)

Blossom wilt (*Sclerotinia laxa* and *Sclerotinia fructigena*)

Blossom wilt (*Sclerotinia laxa* and *Sclerotinia fructigena*)

**Plant Disease and Pathogen** 

**Olive** Leaf spot (*Cycloconium oleaginum*)

**Nectarine**

**Passion fruit** 

**Peach**

**Pear**

**Plum**

**Raspberry**

**Grapevine** 


Bitter rot (*Glomerella cingulata*)

Scab (*Venturia cerasi*)

Blight (*Endothia parasitica*)

Leaf scorch (*Gnomonia erythrostoma*) Leaf spot (*Coccomyces hiemalis*)

Shot hole (*Clasterosporium carpophilum*)

Ink disease (*Phytophthora cambivora*)

Mal secco (*Deuterophoma tracheiphila*)

Melanose (*Diaporthe citri*) Scab (*Elsinoe fawcetti*)

**Currant (Ribes)** Leaf spot (*Mycosphaerella grossulariae* and *Mycosphaerella ribis*) Leaf spot (*Pseudopeziza ribis*)

Rust (*Cerotelium fici*)

Die back (*Botrytis cinerea*)

**Fruit trees** Crown gall (*Bacterium tumefaciens*)

Septoria spot (*Septoria depressa*) Sooty blotch (*Leptothyrium pomi*) Sooty mould (*Aithaloderma citri*) Thread blight (*Corticium koleroga*)

Blight (*Phizoctonia microsclerotia*) Canker (*Phomopsis cinerescens*)

Thread blight (*Corticium koleroga*)

Leaf fall and Fruit rot (*Cercospora bolleana*)

American mildew (*Sphaerotheca mors-uvae*) Cluster cup rust (*Puccinia pringshemiana*)

Anthracnose (*Colletotrichum gloeosporioides*) Anthracnose (*Gloeosporium mangiferae*) Bacterial black spot (*Erwinia mangiferae*) Powdery mildew (*Oidium mangiferae*) Red rust (*Cephaleuros virescens*) Scab (*Elsinoe mangiferae*)

Leaf spot (*Mycosphaerella grossulariae*)

Black pit (*Pseudomonas syringae*) Black spot (*Phoma citricarpa*) Brown rot (*Phytophthora* spp.) Canker (*Xanthomonas citri*)

Anthracnose (Wither tip) (*Gloeosporium limetticola*)

Bacterial canker (*Pseudomonas mors-prunorum*)

Brown rot (Blossom wilt) (*Sclerotinia laxa* and *Sclerotinia fructigena*)

**Plant Disease and Pathogen** 

**Cherry**

**Chestnut** 

**Citrus**

**Fig**

**Gooseberry**

**Mango**


Copper in Horticulture 269

Ring spot (*Marssonina panattoniana*)

Dry rot (*Sclerotium rolfsii*) Early blight (*Alternaria solani*) Grey mould (*Botrytis cinerea*)

Black spot (*Diplocarpon rosae*) Downy mildew (*Peronospora sparsa*)

Mildew (*Sphaerotheca pannosa*) Rust (*Phragmidium mucronatum*)

Downy mildew (*Peronospora effusa*)

Downy mildew (*Peronospora schactii*)

Black rot (Die back) (*Botryodiplodia theobromae*)

Wilt (*Sclerotinia sclerotiorum*)

Blister blight (*Exobasidium vexans*) Grey blight (*Pestalotia theae*) Red rust (*Cephaleuros niycoidea*)

Early blight (*Alternaria solani*) Foot rot (*Phytophthora cryptogea*) Fruit rot (*Didymella lycopersici*) Fruit rot (*Phytophthora capsici*) Grey leaf spot (*Stemphylium solani*) Leaf mould (*Cladosporium fulvum*) Leaf spot (*Septoria lycopersici*) Mildew (*Leveilluia taurica*) Table 3. List of diseases and pathogens at some horticultural plants suitable to control with

Anthracnose (*Colletotrichum phomoides*) Bacterial spot (*Xanthomonas vesicatoria*) Blight (Late blight) (*Phytophthora infestans*)

Blight (Late blight) (*Phytophthora infestans*)

Leaf spot (Anthracnose) (*Sphaceloma rosarum*)

**Plant Disease and Pathogen** 

**Lettuce** Downy mildew (*Bremia lactucae*)

**Spinach** Leaf spot (*Heterosporium variabile*)

**Sugar beet** Leaf spot (*Cercospora beticola*)

**Sunflower** Rust (*Puccinia helianthi*)

**Sweet potato** Wilt (*Fusarium* spp.)

**Persimmon** Canker (*Phomopsis diospyri*)

**Potato**

**Rose** 

**Tea** 

**Tomato**

copper fungicides

**Onion** Downy mildew (*Peronospora destructor*)


Blight (*Xanthomonas juglandis*) Ring spot (*Ascochyta juglandis*)

Chocolate spot (*Botrytis cinerea*)

Anthracnose (*Colletotrichum lindemuthianum*) Common blight (*Xanthomonas phaseoli*)

Powdery mildew (*Erysiphe polygoni*) Rust (*Uromyces appendiculatus*)

Black leg (Canker) (*Phoma lingam*) Black rot (*Xanthomonas campestris*) Damping off (*Oipidium brassicae*) Downy mildew (*Peronospora parasitica*)

Bacterial soft rot (*Bacterium carotovorum*)

Anthracnose (*Colletotrichum lagenarium*) Black rot (*Mycosphaerella citrullina*)

Leaf blight (*Alternaria cucumerina*)

Wilt (*Erwinia tracheiphila*)

Red thread (*Corticium fusiforme*) Snow mould (*Calonectria graminicola*) Stripe smut (*Ustilago striiformis*)

Downy mildew (*Pseudoperonospora cubensis*)

Powdery mildew (*Erysiphe cichoracearum*) Stem end rot (*Physalospora rhodina*) Wet rot (*Choanephora cucurbitarum*)

Brown patch of lawns (*Rhizoctonia* and *Holminthosporium* spp.)

Blight (*Alternaria dauci*) Leaf spot (*Cercospora carotae*)

Halo blight (*Pseudomonas medicaginis* var*. phaseolicola*)

Leaf spot (*Asochyta pisi*) Rust (*Uromyces fabae*)

Anthracnose (Blotch) (*Gnomonia leptostyla*) Downy leaf spot (*Microstroma juglandis*)

**Plant Disease and Pathogen** 

**Artichoke (Globe)** *Ramularia cynarae*  **Asparagus** Rust (*Puccinia asparagi*)

**Walnut**

Vegetable and others

**Bean (French and Runner)** 

**Bean (Broad)**

**Brassicas**

**Carrot**

**Cucurbits**

**Grasses**

**Vine (Sultana)** Sooty dew (*Exosporium sultanae*)


Table 3. List of diseases and pathogens at some horticultural plants suitable to control with copper fungicides

Copper in Horticulture 271

a black-brown crystal or amorphous powder. It is used in making fibres and ceramics and for welding fluxes. Cu2O presents one of the principal oxides of copper. The most common preparation of cuprous oxide is by oxidation of copper metal 4 Cu + O2 → 2 Cu2O; 2 Cu + O2 → 2 CuO, commercially however also by reduction of copper(II) solutions with sulfur dioxide, the final product of which is reddish mineral cuprite. Cuprous oxide is commonly used as a pigment (colouring of porcelain and glass), a fungicide (seed dressings) and an antirust protection agent for marine paints. Available on the market are copper(II)

Synonyms of cuprous oxide are yellow cuprocide; red copper oxide; dicopper monoxide; dicopper oxide; brown copper oxide; copper hemioxide; Copper nordox; copper protoxide; copper suboxide; cuprite; cuprocide; fungimar; dikupferoxid (German); óxido de dicobre

Copper(II) chloride is a light brown solid chemical compound with the formula CuCl2 and has the potential of slowly absorbing moisture and forming a blue-green dihydrate., The aqueous solution prepared from copper(II) chloride contains a range of copper(II) complexes depending on concentration, temperature, and the presence of additional chloride ions. Copper(II) chloride occurs as a very rare mineral in nature, tolbachite and the dihydrate eriochalcite, more common however are mixed oxyhydroxide-chlorides, like atacamite Cu2(OH)3Cl. There are few preparations of cupric chloride known, used as

CuCl2 is a yellowish to brown, deliquescent powder soluble in water, alcohol and ammonium chloride, used as a mordant in dyeing and printing textiles. CuCl consists of fine grey-black pearls with size of a few hundred µm and a copper content of 64 %. Copper(II) chloride dihydrate (CuCl2 x 2H2O) is built up of blue-green crystals, soluble in water and has a copper content of approx. 37 %. Anhydrous copper(II) chloride is a brown crystal powder, soluble in water and highly hygroscopic, with a copper content of approx. 47 %. Synonyms of cupric chloride; copper(II) chloride; dichlorocopper, Kupferdichlorid

Copper(I) chloride, known also as lower chloride of copper with the formula CuCl (Mr = 99.03 g mol-1) or Cu2Cl2 (Mr = 198.05 g mol-1), is a white solid substance partially soluble in water, but totally in concentrated hydrochloric acid. In middle of 17th century cuprous chloride was first produced by Robert Boyle from mercury(II) chloride and metal Cu: HgCl2 + 2 Cu → 2 CuCl + Hg. Later Proust J.L. prepared CuCl by heating CuCl2 at red heat in absence of air, causing it to lose half of its combined chlorine, followed by removing residual CuCl2 by rinsing with water, and by the application which was widely used for heating and lighting. During the 19th and early 20th Centuries the acidic solution of CuCl

oxides with a copper content of around 78 %.

(Spanish); oxyde de dicuivre (French).

fungicide in agriculture as well:

**4.1.5 Cuprous chloride** 

a. chlorination of copper: Cu + Cl2 + 2 H2O → CuCl2(H2O)2,

(German); dicloruro de cobre (Spanish); dichlorure de cuivre (French).

b. treatment of Cu hydroxide, oxide or Cu(II) carbonate with hydrochloric acid, c. anhydrous CuCl2 prepared directly by the union of copper and chlorine and d. by crystallization of torrid dilute hydrochloric acid, cooling in CaCl2-ice bath.

**4.1.4 Cupric chloride** 

#### **4.1.2 Copper acetates**

Copper(II) acetate is also known as cupric acetate with the chemical formula Cu(OAc)2, where OAc- stands for acetate (CH3CO2 -). Since ancient times copper acetates of some form have been used as fungicides (greenish colour), whereas nowadays more frequently as reagents for syntheses of many inorganic and organic compounds. Copper acetate is odourless and efflorescent. It is soluble in alcohol and slightly soluble in ether and glycerol. The commercially available copper acetates are these in hydrated forms (Cu(C2H3O2)2 H2O); Mr = 199.67 g mol-1) which contain one molecule of water for each atom of Cu. The production of copper acetates first appeared in France, where the term of "verdigris" (*verte grez*) was applied. At grape remaking and wine production copper metal sheets were used, and when the surface of copper sheets exposed to the air for some days, they had become coated with verdigris, which were removed, and then replaced. The obtained product was known as blue verdigris and in a concentration of 1 kg of basic copper acetate in 500 litres of water; it was used as a fungicide. It contains approx. 32 % of copper and crystallises with 1 mol crystal water. Nowadays it is prepared by dissolving cupric oxide or a copper carbonate in acetic acid; however it can be produced also by treating a copper sulphate solution with lead acetate or by the reaction of acetic acid and copper with subsequent crystallization.

Until the 19th century, verdigris coincidentally happened to be the most vibrant green pigment available and was therefore frequently used in painting. Copper acetates of different chemical compositions make up pigments, colours from green to green-blue, bluegreen, and finally blue. Reactions with copper acetate vary among substances such as the following: copper acetates dissolve in mineral acid, alkalis convert them into blue copper hydroxide, oils, resins and proteins react to form green transparent copper oleates, resinates, and proteinates.

Neutral Verdigris is neutral copper acetate which occurs when basic acetates are dissolved in acetic acid, or when basic verdigris is ground up with strong acidic acid. Basic verdigris forms from the combination of air, water vapour, acetic acid vapour, and copper or copper alloy mix. It forms a solid of blue, or blue-green material. It is often made up of fine needles. The chemical formula for basic verdigris can include all of the following (Kühn, 1997):

> [Cu(CH3COO2]2. Cu(OH)2. 5H2O (blue) Cu(CH3COO)2. Cu(OH)2. 5H2O (blue) Cu(CH3COO)2. [Cu(OH)2]2 (blue) Cu(CH3COO)2. [Cu(OH)2]3. 2H2O (green)

Synonyms of cupric acetate are acetate cuivrique (DOT French); acetato cuprico (DOT Spanish); acetic acid cupric salt; acetic acid, cupric salt; copper acetate; copper acetate (Cu(C2H3O2)2); copper acetate (Cu (MCO2)2); copper acetate (Cu(OAc)2); copper diacetate; copper (II) acetate; copper (II) diacetate; copper (II) acetate; crystallized verdigris; crystals of venus; cupric acetate monoydrate; cupric diacetate; neytral verdigris; and venus copper.

#### **4.1.3 Cuprous oxide**

Cuprous oxide is an inorganic compound of two known forms: copper(I) oxide (Cu2O; Mr = 143.08 g mol-1), in nature present as cuprite, dark red crystals or granular powder, formed on copper by heat, and cupric oxide copper(II) oxide (CuO; Mr = 79.55 g mol-1),

Copper(II) acetate is also known as cupric acetate with the chemical formula Cu(OAc)2,

have been used as fungicides (greenish colour), whereas nowadays more frequently as reagents for syntheses of many inorganic and organic compounds. Copper acetate is odourless and efflorescent. It is soluble in alcohol and slightly soluble in ether and glycerol. The commercially available copper acetates are these in hydrated forms (Cu(C2H3O2)2 H2O); Mr = 199.67 g mol-1) which contain one molecule of water for each atom of Cu. The production of copper acetates first appeared in France, where the term of "verdigris" (*verte grez*) was applied. At grape remaking and wine production copper metal sheets were used, and when the surface of copper sheets exposed to the air for some days, they had become coated with verdigris, which were removed, and then replaced. The obtained product was known as blue verdigris and in a concentration of 1 kg of basic copper acetate in 500 litres of water; it was used as a fungicide. It contains approx. 32 % of copper and crystallises with 1 mol crystal water. Nowadays it is prepared by dissolving cupric oxide or a copper carbonate in acetic acid; however it can be produced also by treating a copper sulphate solution with lead acetate or by the reaction of acetic acid and copper with subsequent crystallization.

Until the 19th century, verdigris coincidentally happened to be the most vibrant green pigment available and was therefore frequently used in painting. Copper acetates of different chemical compositions make up pigments, colours from green to green-blue, bluegreen, and finally blue. Reactions with copper acetate vary among substances such as the following: copper acetates dissolve in mineral acid, alkalis convert them into blue copper hydroxide, oils, resins and proteins react to form green transparent copper oleates, resinates,

Neutral Verdigris is neutral copper acetate which occurs when basic acetates are dissolved in acetic acid, or when basic verdigris is ground up with strong acidic acid. Basic verdigris forms from the combination of air, water vapour, acetic acid vapour, and copper or copper alloy mix. It forms a solid of blue, or blue-green material. It is often made up of fine needles. The chemical formula for basic verdigris can include all of the following (Kühn, 1997):

[Cu(CH3COO2]2. Cu(OH)2. 5H2O (blue) Cu(CH3COO)2. Cu(OH)2. 5H2O (blue) Cu(CH3COO)2. [Cu(OH)2]2 (blue) Cu(CH3COO)2. [Cu(OH)2]3. 2H2O (green) Synonyms of cupric acetate are acetate cuivrique (DOT French); acetato cuprico (DOT Spanish); acetic acid cupric salt; acetic acid, cupric salt; copper acetate; copper acetate (Cu(C2H3O2)2); copper acetate (Cu (MCO2)2); copper acetate (Cu(OAc)2); copper diacetate; copper (II) acetate; copper (II) diacetate; copper (II) acetate; crystallized verdigris; crystals of venus; cupric acetate monoydrate; cupric diacetate; neytral verdigris; and venus copper.

Cuprous oxide is an inorganic compound of two known forms: copper(I) oxide (Cu2O; Mr = 143.08 g mol-1), in nature present as cuprite, dark red crystals or granular powder, formed on copper by heat, and cupric oxide copper(II) oxide (CuO; Mr = 79.55 g mol-1),


**4.1.2 Copper acetates** 

and proteinates.

**4.1.3 Cuprous oxide** 

where OAc- stands for acetate (CH3CO2

a black-brown crystal or amorphous powder. It is used in making fibres and ceramics and for welding fluxes. Cu2O presents one of the principal oxides of copper. The most common preparation of cuprous oxide is by oxidation of copper metal 4 Cu + O2 → 2 Cu2O; 2 Cu + O2 → 2 CuO, commercially however also by reduction of copper(II) solutions with sulfur dioxide, the final product of which is reddish mineral cuprite. Cuprous oxide is commonly used as a pigment (colouring of porcelain and glass), a fungicide (seed dressings) and an antirust protection agent for marine paints. Available on the market are copper(II) oxides with a copper content of around 78 %.

Synonyms of cuprous oxide are yellow cuprocide; red copper oxide; dicopper monoxide; dicopper oxide; brown copper oxide; copper hemioxide; Copper nordox; copper protoxide; copper suboxide; cuprite; cuprocide; fungimar; dikupferoxid (German); óxido de dicobre (Spanish); oxyde de dicuivre (French).
