Fungal diseases are the major threat to crop production. As per one estimate by Alexander et al (2017), one in every eight crops fail to give desired yield due to fungal diseases. In some instances the yield loss is more than 50%. Estimated yield loss by fungal infection globally is 10-23% in field and the same is 10-20% in post harvest stage. Sometimes fungal disease cause havoc, like in case of 'Great Irish potato Famine' lasted from the year 1845 to 1852. Phytopthora infestans was the proximate cause of Irish famine, resulted in starvation and death of millions of people.

        Along with the main damage, the fungal infections has various secondary effects like survival of inoculum and posing threat to succeeding crops, loss of vigor, defoliation and death of branches or stems leading loss in terms of quantity and quality. Ability of fungi to adapt new climate and develop resistance to fungicides posing greater challenges to crop productions. Emerging of new strains of pathogens and their hybridization with existing are the constrains agriculture researcher and scientist. 

         Leaf spots, rusts, powdery and downy mildew, cankers are the various types of fungal disease.  Easy, quick and effective way to control these anomalies are application of fungicides.

         Fungicides are those substances which control fungi causing damages to crops, leading to economic losses or endanger human and animals in any form. Fungicides are mostly synthetic chemicals in composition and occasionally biological or plant based. Fungicides controls the fungal diseases by killing the spores of parasitic fungal pathogens. They belong to different chemical groups and of various formulation. They vary in mode of action as well.

FUNGICIDES AND THEIR CLASSIFICATION AND GROUPS

CLASSIFICATION OF FUNGICIDES:

           Fungicides are classified into different types or groups  based on their mode of action, mode of applications and chemical componets.

Fungicides based on their application:

Soil Fungicides:

        Soil fungicides are those, applied to soil to control the fungal infections. There are applied before ( Chloropicrin, formadihide, vapum, Coper oxychoride, etc)  or after planting.   

Seed protectants:

            Seed protectants are used to   treat seed or  propagating materials,  before they are sown or planted.  There are fungicides in the form of  Capton, Thiram, carbendazem,  to use as seed protectants.  Seed treatment  is a preventive way of  fungal disease management.

Foliar fungicides:

       Foliar or foliage fungicides are those applied on leaves and shoots  to control fungal disease.  These are mainly contact fungicides. 

Wound dresser fungicides:

         Wound dressing  fungicides are applied to wound or cut on the plants, so as to restrict the possible entry of fungal pathogens or spores. Wound or cut occurred during  by pruning or removal of infected portion or by insect damage are applied with such fungicides. Bordeaux mixture or Chaubatia pastes are the popular wound dresser.

CLASSIFICATION OF FUNGICIDES BASED ON CHEMICAL COMPOSTION:

        Fungicides are mostly chemical compounds,  known for their quick and effective actions  in controlling plant fungal diseases. There are specific chemical ingredients which are responsible for the fungicidal activities of  of fungicides. Copper, mercury, zinc, tin and nickle are the metals used in preparation of fungicidal formulations, either in form of salts or organic acids or organic compounds. Hetero-cyclic nitrogenous compounds, quinones, Sulphur, Chlorines, phosphorous are the non metals used in fungicides as their active ingredients.

Sulphur Based Fungicides:

           Sulphur based fumgicides are either of organic sulphur or inorganic sulphur based. In case of inorganic sulphur, it is used in elemental or as lime sulphur and  dust or wettable sulpur. Sulfur fungicides have been found effective against powdery mildew kind of fungal diseases and also some specific  rust and leaf blights. 

          Sulphur dust is an example for elemental form of sulphur fungicides, available with trade names Cosan, Wetslf, Microsul. These are used  as contact and protective fungicides, effective against powdery mildew of fruits, vegetables and flowers and rust disease in field crops.  Lime sulphur also a elemental sulphur fungicide, used as protectant in powdery mildew.  Lime sulphur can be prepared by mixing 9 kg of rock lime and 6.75 kg of sulphur in 225 litres of water.

        Organic sulphur fungicides are otherwise known as Carbamate fungicides and  are the derivatives of Dithiocarbamic acids. Organic sulphur fungicides are classified into  two different groups like Mono alkyl Dithiocarbamates and Dialkyl Dithiocarbamates.

Monoalkyl Dithiocarabamate Fungicides:

 Mono Alkyl Dithiocarbamate  are  organic sulphur group of  fungicides Which includes some of the important  fungicides like Zineb, Maneb, Mancozeb,  Nabam, Vapum.

Zineb: It is chemically Zinc Ethylene bisdithiocarbamate, available in trade names like Du Pant Fungicide A, Poly ram. These group of fungicides  are effective against Early and Late blight of potato and tomato,  Rice blast, Fruit rot in Chilli, downy mildew and rusts in cereals.

 Maneb: Maneb is chemically Manganese ethylene bisdithiocarbamate.   Available  in trade  names like  Dithane  M22,  Manzatte  WP  and  MEB.

Mancozeb: It is a combination of  Maneb with Zinc ion. It is available in market with the trade names like  Dithane M45, Indofil M45, Manzeb.

Both Maneb and Mancozeb are effective against rust disease of pulses,  downy mildew and Anthracnose of vegetables,  blights of potato and tomato. These are broad spectrum fungicide which can be used to control various fungal diseases in various filed crops, vegetables, fruit crops.

 Nabam: Chemically Nabam is Di Sodium Ethylene bidithiocarbamate.  Available in trade manes like Dithane A-40, Dithane-D14, Chembam, etc. These are  used in foliar applications to control leaf spot diseases in vegetables and fruits.  They are also effective in  soil application to control pathogens like Phythium, Phytopthera and fusarium. It has also found effective to control algal growth in paddy field.

   Vapum: Chemically vapum is Sodium methyl Dithiocarbomate.  Available in trade names like VPM, Vapum,  Chemvape,  Karbation 4-S, Vita Fume. Used for soil application before sowing to take care of weeds, soil born fungus and insects.

Mercury based fungicides:

          Mercury based fungicides show high level of toxicity along with high level residual toxicity and have been banned in many counties. In India, it is restricted to use only seed treatment for certain crops. Mercury based fungicides are of two types Organic mercury and inorganic mercury compounds.

Mercuric Chloride and Mercurous Chlorides are the organic mercury based fungicides and available in different trade names. Merfusan and Mersil are the examples of Mercuric Chloride type of fungicides, used in seed treatment of potato tubers and some other tuber crops.

Cyclosan and M-C turfs are Mercurous Chloride type of fungicides which are restricted to soil applications.

Organomercurials: These are the organic mercury based fungicides. Ethyl Mercury Chloride, Phenyl Mercury Chloride, Methoxy Ethyl mercury Chlorides and Tonyl Mercury Acetate are the some in this group.

Ethyl Mercury Chloride: It is available in the trade name like Ceresan

Phenyl Mercury Chloride: Available in trade name Ceresan Dry (India), Ceresol, Leytosan.

Methoxy Ethyl mercury Chlorides: Available in trade names like Agallol, Aretan, Emisan, Ceresan wet.

Tonyl Mercury Acetate: Available in trade name Agrosol GN

Copper Based Fungicides:

             Use of copper based fungicide become more evident with the discovery of Bordeaux Mixture, a mixture of copper sulphate and lime, in France by Millardet in 1985. The Same was found effective against downy mildew of grapevine and Late Blight of Potato. Borduaux paste,  Burgandy mixture and Cheshnut compound were next to come and played effective role in control of fungal diseases. Copper Oxy- Chlorides, which is relatively new formulation, an insoluble compound, also proved effective against  several diseases.

Copper based fungicides are broadly classified as  Copper Sulfate based  and Copper Carbonate based. 

Copper Sulfate based Preparation:

1. Bordeaux Mixture: Prepared by mixing 1kg of Copper Sulphate and 1 kg of lime in 100 ltrs of water. It is effective as protective fungicide and used as foliar spray.

2. Bordaeux Paste: It is prepared by mixing 1kg of Copper Sulphate and one kg of lime in 10 Ltr of water. It is commonly used as wound dresser to avoid entry of fungal pathogen, usually after pruning.

3. Burgundy Mixture: It is prepared by mixing of 1kg of copper Sulphate and 1 kg of Sodium carbonate in 100 ltrs of water. it can be used in those crops sensitive to bordaex mixture.

4. Chesnut Compound: It is prepared by mixing 2 parts of copper sulphate and 11 parts of ammonium carbonate. Mixture has to be stored airtight overnight.  It is used for soil application especially against Phytium and Rizoctonia kind of fungi.

Copper Carbonate based Preparation:

1. Chaubattia Paste: It is a mixture of 800 gm each red lead and Copper Carbonate in 1 ltr of linseed oil or lanolin. This mixture has been found effective against canker , pink disease and color rot of apple, peach and pear. Paste can also be used as wound dresser.

2. Cuprous Oxide: It is available in trade names like fungimar, Perenox, Copper Sandoz, Copper 4% dust, Perecot, Cuproxd, Kirt i copper. These are used as protective fungicides as foliar sparay, seed treatment against rust, blight and downy mildew.

3.Copper oxychloride: Blitox, Cupramar 50%WP, Fytolan, Bilmix 4%, Micop D-06, Micop W-50, Blue copper 50, Cupravit, Cobox,       Cuprax,  Mycop. These are known for effective control of many leaf spots and leaf blight diseases.

Hetercyclic Nitrogen Compound Fungicides:

         Heterocyclic Nitrogen compound based fungicides are effective as foliage  and fruit fungicides. Captan, Gyodin, Captafol and folpet are some of the important fungicides under this group.

     Captafol: This is the fungicide of  protective in action. These are commonly available in trade names like Foltaf, Difolaton, Difosan, Captaspor, Sanspor, Folcid, Pillarton, etc. These have been reported  effective in controlling fungal diseases in tomato and coffee.

    Captan:  Captan type of fungicides are commonly used seed dresser against rot and damping off disease in fruits, ornamentals and vegetables. These are available in trade names like Captan 75 W, Captan 50 W, Essofingicide 406, Orthocide 406, Varacide 89, Deltan, Merpan, Hexa cap, Agrox, Merpan, Clomitane and others.

    Gyodine: Gyodines are narrow spectrum fungicides commonly used to control Apple Scab and leaf spot in cherry leaf. Gyoxilindane, Glyoxide, Gyodin, Gyoxide dry, Gydex-30, Melprex, Sulgen.

Bengene Based Fungicides:

         Benzene, an aromatic compound exhibits some sort of anti-fungal properties and  the same is used in plant disease control. Quintozene, Dichloram, Fenaminsosulph are the import fungicides under this group.

Quintozenes: Available in trade names like Brassicol, Terrachlor, Tritisan-10%, 20%, 40% Dust and 75% WP, PCNB 75WP. Mainly used for seed and soil treatment against Botrytis, Scerotium, Rhizoctonia and Scerotina Sps.

Dichloran: These are effective against fungal pathogens like Botrytis, Scerotium and Rhizoctonia Sps. This group includes fungicides like Allisan, Botran 50% and 75% WP.

Fenaminsosulph: Includes fungicides trade names like Karathane, Arathane, Crotothane, Mildex, etc. Useful in safeguarding germinating seeds and establishing seedlings. They protect the plants from powdery mildew.

Quinone Fungicide:

       Quinone fungicides are considered as effective seed protectant. Important fungicides in the group are Chloranil and Dichlone.

Choranil: Available with trade name Spergon. Effective against smut of barley and Sorghum and kernel bunt of wheat when used for seed treatment

Dichlone: Commonly used as seed protectant and occasionally for foliar spray against peach leaf curl and Apple cab disease.

Organo Tin Compounds:

           Organo tin Compounds also exhibits certain anti fungal and anti bacterial properties. This group includes Fentin hydroxide , Fentin Acetate and Fentin Chloride type of fungicides. Fentin Acetate group include fungicides like Brestan WP 40% and 60%. Considered specifically effective against Ramularia Sps in celery and Anthracnose and Downy mildew in Sugar Beet, anthracnose in bean.

         Fentin Chloride type includes Brestonol 45% WP and Tinmate. These are found effective against Cercosproa leaf spot in Sugar beat and Blast disease in Paddy.

        Fentin Hydroxide type includes fungicides bearing trade name like Fermatin, Du-ter, Du-terforte, Tubotin. These are effective against blast in paddy, Tikka disease in ground nut, Potato leaf blight and Sugar beat leaf spot.

SYSTEMIC FUNGICIDES:

          Systemic fungicides are chemical compounds which trans-locate in plant vascular system and can reach remotely located fungal pathogens to kill or control them. These can be used in different ways and means,   from seed treatment to foliage spray. These help in eradicating established fungal pathogens and prevents their  spread to new plant parts or plants.

       Systemic fungicides are grouped into Benzimidazoles, Thiophanates, Oxathiins related compounds, pyrimidines, morpholines, organo-phosphorus related compounds based on their chemical composition and structures.

Benzimidazole Fungicides:

       Benzimidazole fungicides are known for their broad spectrum activities. Benomyl , Carbendazim, Thiabendazole, Fuberidazole are popular fungicides included in this group.

Benomyl is available in trade name benomyl itself and Benlate 50 WP

Carbendazim is available in trade name of Bavistin 50 WP, MBC, Bersol, B-Sten 50, Zoom, Tagstin , Agrozim, Jkenstin, etc

Thiobenzazole available in trade names like Mertect, Tecto, Storite, Thiobenadazole, etc

Fuberidazole is available in trade name Voronit

Thiophanate Group of Fungicides:

        Thiophante group of fungicides are Thiourea based systemic fungicides and derived from Thioallophanic acid. Important fungicides included in this group are Halt, Cavalier,  Topsin 50 WP, Cercobin 50 WP, Enovit, Topsin M70 WP, Cercobin M70 WP, Mildothane and Envovit-Methyl. These are known for their broad spectrum activities. They are found effective against Yellow Sigatoka in banana, powdery mildew causing pathogens in cucurbits, vines, apple pears. 

Morpholine Group of Fungicides:

          These are the systemic fungicides includes fungicide with the trade names Calixin 75 EC, Bardew, Beacon, BAS 238 F. These are found effective against powdery mildew in vegetables, ornamentals and cereals and Mycospharella musicola in banana. BAS 238 F is specially effectice against powdery mildew in ornamental and floriculture plants.

Pyrimidine, Pyridine, Piperridine, Imiddazole Group of Fungicide:

          These group of fungicides are effective against powdery mildew and rust of many crops. This group  includes fungicides like Bayleton, Amiral, Baytan, Terrazole,  Terrazole ,  Koban, Pansol EG, Pansol 4% DP, Turban WP. 

Hydroxy Pirimidines Fungicides:

         These group of fungicides are effective against powdery mildew of various crops. Ethirimol and Dimethirimol are important type of fungicides included in the group. Milliatem 80 WP, Milcurb super and milgo are important fungicides under this group.

Furan Derivative Fungicides:

             Furan derivative fungicide includes Furcarbanil and Cyclafuramid.  Furcarbanil is effective against loose smut of barley and wheat, rust of vegetables. It is used for  seed treatment  or soil applications. Cyclafurmid is known for its effective control of smut, rust and bunts in cereals, leaf rust of coffee, blister blight of tea, Fusarium oxysporum  in  tomato, Black surfs  in potato and damping off in tomato and Armillaria sps in woody plants.

Benzanilide Derivatives:

          This group of fungicide includes fungicide Mebenil and Benodanil. Mebenil  has been found effective against yellow rust of wheat and barley, brown rust of barley. Effective against Sclerotium rolfsli, a soil born fungus affecting various crops  and Rhizoctonia. Benodanil is available in trade name like calirus which is proved effective against rust of cereals, root rot, downy mildew and blight in ornamental crops. These group of fungicides are also found effective as acaricides.

Organo-phosphorous Group of Fungicides:

Organo Phosphorous group of fungicides include mainly Pyrazophos and Iprobenphos. Pyrazophos gruop includes fungicides like Curamil WP, Missile EC and Afugan and known for controlling of powdery mildew of fruits, vegetables and ornamental. Iprobenphos mainly include Kitazin 48% EC, Kitazin 17 G, Kitazin 2% D. These fungicide are known for effectiveness against rice blast and rice sheath blight.

Piperazine Group of Fungicide:

Piperazine group of fungicides include fungicides like Fungitex and Saprol EG. These are effective against scab and powdery mildew diseases in fruits and also to control storage diseases of fruits.

Phenol Derivative Fungicides:

Phenol Derivative fungicides consists of Demonsan 65 WP, Tersan SP and Turf. These are found highly effective against disease caused by Rhizoctonia sps. like brown rot in different crops.

Fungicides of Miscellaneous Group

Metalaxyl: This group of fungicides are found effective against fungal disease caused by Oomycete fungi like downy mildew, leaf blight, damping off, root rots.  This group  Includes fungicides like Apron 35 SD and Ridomil.

Combination of Metalaxyl and Mancozeb: It is combination of two fungicides systemic and contact in nature.  Available in trade name Ridomil MZ 72 WP (8% Metalaxyl and 64% Mancozeb). It is effective against damping off, root   rot stem rot and downy mildew of grapes  and millet.

Tricyclazole: Available in trade name Beam, Blacides, etc. It is specifically effective against paddy blast with both preventive and curative actions.

Fosetyl-AI: Available in trade names like  Alliette 80 WP, effective against disease like root rot, stem rot and fruit rot and phytopthora disease of citrus, rubber, pepper and downy mildew of Grapes.

Hexaconozole: The group  consists of fungicides like Contaf 5% EC and Anvil 5% EC, Hexazole, Hexamax and others. These are effective against powdery mildew and rust of several crops. Effectively controls some seed born and soil born diseases caused by Ascomycetes and Basidiomycetes fungi.

Triazbutyl Oxide: This selectively effective against leaf rust of wheat caused by Puccina recondita. It is also an effective molluscicide and wood preservative.

Propicanazole: Available in trade name like Tilt 25 EC, Pinade, Propiguard, Zetox, etc. Found very effective against Sigatoka of Banana. Also effective in controlling powdery mildew, rust and leaf spot disease of various crops.

Terbuconazole: Available in the name Folicur 25EC, Orius, Tebustar,   Raxil 2DS, and others.  and are effective against  rust, sheath blight, anthracnose and powdery mildew. 

Penconazole:Available in trade name Tofas 10EC and is effective against powdery mildew of various ornamental, fruit and vegetable crops. 

Pyroquilon: Available in trade name Fongorene 50 WP and specifically effective against rice blast.