Fungicides are

pesticide Pesticides are substances that are used to control pests. They include herbicides, insecticides, nematicides, fungicides, and many others (see table). The most common of these are herbicides, which account for approximately 50% of all p ...

s used to kill

parasitic fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as one of the traditi ...

or their

spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...

s. Fungi can cause serious damage in

agriculture Agriculture encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created ...

, resulting in losses of yield and quality. Fungicides are used both in agriculture and to fight fungal infections in animals, including humans. Fungicides are also used to control

oomycetes The Oomycetes (), or Oomycota, form a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms within the Stramenopiles. They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction o ...

, which are not

taxonomically In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon), and these groups are given ...

/genetically fungi, although sharing similar methods of infecting plants. Fungicides can either be contact, translaminar or systemic. Contact fungicides are not taken up into the plant tissue and protect only the plant where the spray is deposited. Translaminar fungicides redistribute the fungicide from the upper, sprayed leaf surface to the lower, unsprayed surface. Systemic fungicides are taken up and redistributed through the xylem vessels. Few fungicides move to all parts of a plant. Some are locally systemic, and some move upward. Most fungicides that can be bought retail are sold in liquid form, the active ingredient being present at 0.08% in weaker concentrates, and as high as 0.5% for less potent fungicides. Fungicides in powdered form are usually around 90% sulfur.

Major fungi in agriculture

Some major fungal threats to agriculture (and the associated diseases) are

Ascomycetes Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The de ...

("potato late blight"),

basidiomycetes Basidiomycota () is one of two large division (mycology), divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. Mor ...

powdery mildew Powdery mildew is a fungus, fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of Ascomycota, ascomycete fungi in the order Erysiphales. Powdery mildew is one of the easier plant disea ...

"),

deuteromycetes The fungi imperfecti or imperfect fungi are fungi which do not fit into the commonly established taxonomic classifications of fungi that are based on biological species concepts or morphological characteristics of sexual structures because their ...

(various rusts), and

downy mildew Downy mildew refers to any of several types of oomycete microbes that are obligate parasites of plants. Downy mildews exclusively belong to the Peronosporaceae family. In commercial agriculture, they are a particular problem for growers of c ...

").

Types of fungicides

Like other

pesticides Pesticides are substances that are used to pest control, control pest (organism), pests. They include herbicides, insecticides, nematicides, fungicides, and many others (see table). The most common of these are herbicides, which account for a ...

, fungicides are numerous and diverse. This complexity has led to diverse schemes for classifying fungicides. Classifications are based on

inorganic An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemistry''. Inor ...

(elemental sulfur and copper salts) vs

organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or is the product ...

, chemical structures (dithiocarbamates vs phthalimides), and, most successfully, mechanism of action (MOA). These respective classifications reflect the evolution of the underlying

science Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. Modern science is typically divided into twoor threemajor branches: the natural sciences, which stu ...

Traditional

: 120px, Captan, a phthalimide, is a major commercial fungicide.">phthalimide.html" ;"title="Captan, a phthalimide">Captan, a phthalimide, is a major commercial fungicide. Traditional fungicides are simple inorganic compounds like sulfur, and copper salts. While cheap, they must be applied repeatedly and are relatively ineffective. Other active ingredients in fungicides include neem oil, rosemary oil, jojoba oil, the bacterium ''

Bacillus subtilis ''Bacillus subtilis'' (), known also as the hay bacillus or grass bacillus, is a gram-positive, catalase-positive bacterium, found in soil and the gastrointestinal tract of ruminants, humans and marine sponges. As a member of the genus ''Bacill ...

'', and the beneficial fungus ''

Ulocladium ''Ulocladium'' is a genus of fungi. Species of this genus contain both plant pathogens and food spoilage agents. Other species contain enzymes that are biological control agents. Some members of the genus can invade homes and are a sign of moi ...

oudemansii''.

Nonspecific

In the 1930s

dithiocarbamate In organic chemistry, a dithiocarbamate is a chemical compound with the general formula . It contains the functional group with the Chemical structure, structure . It is the analog of a carbamate in which both oxygen atoms are replaced by sulfur ...

-based fungicides, the first organic compounds used for this purpose, became available. These include

ferbam Iron tris(dimethyldithiocarbamate) is the coordination complex of iron with dimethyldithiocarbamate with the formula Fe(S2CNMe2)3 (Me = methyl). It is marketed as a fungicide. Synthesis, structure, bonding Iron tris(dithiocarbamate)s are typi ...

ziram Zinc dimethyldithiocarbamate is a coordination complex of zinc with dimethyldithiocarbamate. It is a pale yellow solid that is used as a fungicide, the sulfur vulcanization of rubber, and other industrial applications. Applications Known as ziram ...

zineb Zineb is the chemical compound with the formula n. Structurally, it is classified as a coordination polymer and a dithiocarbamate complex. This pale yellow solid is used as fungicide. Production and applications It is produced by treating ethyle ...

maneb Maneb (manganese ethylene-bis-dithiocarbamate) is a fungicide and a polymeric complex of manganese with the ethylene bis (dithiocarbamate) anionic ligand. Health effects Exposure to maneb can occur when breathed in; it can irritate the eyes, ...

, and

mancozeb Mancozeb is a dithiocarbamate non-systemic agricultural fungicide with multi-site, protective action on contact. It is a combination of two other dithiocarbamates: maneb and zineb. The mixture controls many fungal diseases in a wide range of fi ...

. These compounds are non-specific and are thought to inhibit cysteine-based protease enzymes. Similarly nonspecific are N-substituted

phthalimide Phthalimide is the organic compound with the formula C6H4(CO)2NH. It is the imide derivative of phthalic anhydride. It is a Sublimation (phase transition), sublimable white solid that is slightly soluble in water but more so upon addition of bas ...

s. Members include

captafol Captafol is a fungicide.Captafol
from Extension Toxicology Network It is used to control almost all fungal ...

captan Captan is a general use pesticide (GUP) that belongs to the phthalimide class of fungicides. It is a white solid, although commercial samples appear yellow or brownish. Applications Although it can be applied on its own, Captan is often added as ...

, and

folpet Folpet is the tradename for the organic compound with the formula C6H4(CO)2NSCCl3. It is a fungicide derived from phthalimide (C6H4(CO)2N-) and trichloromethylsulfenyl chloride. The compound is white although commercial samples can appear brown ...

Chlorothalonil Chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile) is an organic compound mainly used as a broad spectrum, nonsystemic fungicide, with other uses as a wood protectant, pesticide, acaricide, and to control Mold (fungus), mold, mildew, bacteria ...

is also non-specific.

Specific

Specific fungicides target a particular biological process in the fungus.

Nucleic acid metabolism

bupirimate Bupirimate (systematic name 5-butyl-2-ethylamino-6-methylpyrimidin-4-yldimethylsulphamate; brand names Nimrod and Roseclear 2) is an active ingredient of plant protection products (or pesticides), which has an effect as a fungicide. It belongs to ...

metalaxyl Metalaxyl is an acylalanine fungicide with systemic function. Its chemical name is methyl N-(methoxyacetyl)-N-(2,6-xylyl)-DL-alaninate. It can be used to control '' Pythium'' in a number of vegetable crops, and ''Phytophthora'' in peas. Metalaxy ...

Cytoskeleton and motor proteins

carbendazim Carbendazim is a fungicide, a member benzimidazole fungicides. It is a metabolite of benomyl. The fungicide is used to control plant diseases in cereals and fruits, including citrus, bananas, strawberries, macadamia nuts, pineapples, and pomes. ...

* pencycuron

Respiration

Some fungicides target

succinate dehydrogenase Succinate dehydrogenase (SDH) or succinate-coenzyme Q reductase (SQR) or respiratory complex II is an enzyme complex, found in many bacterial cells and in the inner mitochondrial membrane of eukaryotes. It is the only enzyme that participates ...

, a metabolically central enzyme. Fungi of the class ''Basidiomycetes'' were the initial focus of these fungicides. These fungi are active against cereals. *

azoxystrobin Azoxystrobin is a broad spectrum systemic fungicide widely used in agriculture to protect crops from fungal diseases. It was first marketed in 1996 using the brand name Amistar and by 1999 it had been registered in 48 countries on more than 50 cr ...

binapacryl Binapacryl was used as a miticide and fungicide. Chemically, it is an ester derivative of dinoseb. Although binapacryl has low toxicity itself, it is readily metabolized to form dinoseb, which is highly toxic. International trade in binapacryl ...

boscalid Boscalid is a broad spectrum fungicide used in agriculture to protect crops from fungal diseases. It was first marketed by BASF in 2002 using their brand name Endura. The compound is an biphenyl amide derived inhibitor of succinate dehydrogenase. ...

carboxin Carboxin is a narrow-spectrum fungicide used as a seed treatment in agriculture to protect crops from fungal diseases. It was first marketed by Uniroyal in 1969 using their brand name Vitavax. The compound is a benzanilide analog that combines a ...

* cyazofamid * pydiflumetofen

Amino acid and protein synthesis

blasticidin-S Blasticidin S is an antibiotic that is used in biology research for selectable marker, selecting cells in cell culture. Cells of interest can express the blasticidin resistance genes BSD or bsr, and can then survive treatment with the antibiotic. ...

* kasugamycin * pyrimethanil

Signal transduction

fludioxonil Fludioxonil is a synthetic phenylpyrrole chemical introduced by Ciba-Geigy (now Syngenta) in 1993 for use as a non-systemic fungicide. It is a structural analog of the natural fungicide pyrrolnitrin. It is used for the treatment of crops, particu ...

procymidone Procymidone is a pesticide. It is often used for killing unwanted ferns and nettles, and as a dicarboximide fungicide for killing fungi, for example as seed dressing, pre-harvest spray or post-harvest dip of lupins, grapes, stone fruit, strawberr ...

Lipid synthesis / membrane integrity

propamocarb Propamocarb is a systemic fungicide used for control of soil, root and leaf disease caused by oomycetes. It is used by watering or spraying. Propamocarb is absorbed and distributed through the plant's tissue. Use Propamocarb has fungicidal activit ...

pyrazophos Pyrazophos is an organic compound used as a fungicide and an insecticide. Uses Pyrazophos is a systemic fungicide which is used in orchards, vineyards and vegetable crops against powdery mildew. In some instances, the compound is also an effectiv ...

tecnazene 1,2,4,5-Tetrachloro-3-nitrobenzene (tecnazene) is an organic compound with the formula . It is a colorless solid. A related isomer is 1,2,3,4-tetrachloro-5-nitrobenzene. It is used as a standard for quantitative analysis by nuclear magnetic res ...

Melanin synthesis in cell wall

* tricyclazole

Sterol biosynthesis in membranes

fenpropimorph Fenpropimorph is a morpholine-derived fungicide used in agriculture, primarily on cereal crops such as wheat. It has been reported to disrupt eukaryotic sterol biosynthesis pathways, notably by inhibiting fungal Δ14 reductases. It has also been r ...

hexaconazole Hexaconazole is a broad-spectrum systemic triazole fungicide used for the control of many fungi particularly Ascomycetes and Basidiomycetes Basidiomycota () is one of two large division (mycology), divisions that, together with the Ascomycota, ...

* imazalil *

myclobutanil Myclobutanil is a triazole chemical used as a fungicide. It is a steroid demethylation ( CYP51) inhibitor, specifically inhibiting ergosterol biosynthesis. Ergosterol is a critical component of fungal cell membranes. Stereoisomerism Safety ...

propiconazole Propiconazole is a triazole fungicide, also known as a DMI, or demethylation inhibiting fungicide due to its binding with and inhibiting the Lanosterol 14 alpha-demethylase, 14-alpha demethylase enzyme from demethylating a precursor to ergosterol. ...

Cell wall biosynthesis

dimethomorph Dimethomorph is a fungicide with systemic function. It is used for treating mildew and root rot caused by organisms such as ''Pythium'' and ''Phytophthora ''Phytophthora'' (from Greek (''phytón''), "plant" and (), "destruction"; "the plan ...

polyoxins Polyoxins are a group of peptidyl nucleoside antibiotics. They are a complex produced by ''Streptomyces cacaoi'' var. ''asoensis'' and ''S''. ''piomogenus.'' Polyoxin compounds contain the same base structure but differ in the composition of certai ...

Host plant defence induction

* acibenzolar *

fosetyl-Al Fosetyl-Al is an organophosphorus compound Organophosphorus chemistry is the scientific study of the synthesis and properties of organophosphorus compounds, which are organic compounds containing phosphorus. They are used primarily in pest control ...

phosphorous acid Phosphorous acid (or phosphonic acid) is the Compound (chemistry), compound described by the chemical formula, formula . It is diprotic (readily ionizes two protons), not triprotic as might be suggested by its formula. Phosphorous acid is an in ...

Mycoviruses

Some of the most common fungal crop pathogens are known to suffer from

mycovirus Mycoviruses (Ancient Greek: μύκης ' ("fungus") + Latin '), also known as mycophages, are viruses that infect fungi. The majority of mycoviruses have dsRNA virus, double-stranded RNA (dsRNA) genomes and isometric particles, but approximately ...

es, and it is likely that they are as common as for plant and animal viruses, although not as well studied. Given the obligately parasitic nature of mycoviruses, it is likely that all of these are detrimental to their hosts, and thus are potential

biocontrol Biological control or biocontrol is a method of pest control, controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or phytopathology, plants by bioeffector, using other organisms. It relies o ...

s/biofungicides.

Resistance

Doses that provide the most control of the disease also provide the largest selection pressure to acquire resistance. In some cases, the pathogen evolves resistance to multiple fungicides, a phenomenon known as cross resistance. These additional fungicides typically belong to the same chemical family, act in the same way, or have a similar mechanism for detoxification. Sometimes negative

cross-resistance Cross-resistance is when something develops resistance to several substances that have a similar mechanism of action. For example, if a certain type of bacteria develops antimicrobial resistance to one antibiotic, that bacteria will also have res ...

occurs, where resistance to one chemical class of fungicides increases sensitivity to a different chemical class of fungicides. This has been seen with

and diethofencarb. Also possible is resistance to two chemically different fungicides by separate mutation events. For example, ''

Botrytis cinerea ''Botrytis cinerea'' is a necrotrophic fungus that affects many plant species, although its most notable hosts may be wine grapes. In viticulture, it is commonly known as "botrytis bunch rot"; in horticulture, it is usually called "grey mould" ...

'' is resistant to both azoles and

dicarboximide fungicides Dicarboximide (or dicarboxamide) fungicides are a family of agricultural fungicides that include vinclozolin, iprodione, and procymidone. Dicarboximides are believed to inhibit triglyceride biosynthesis in sclerotia-forming fungi, including ''Bo ...

. A common mechanism for acquiring resistance is alteration of the target enzyme. For example,

Black Sigatoka Black sigatoka is a leaf-spot disease of banana plants caused by the ascomycete fungus ''Mycosphaerella fijiensis'' (Morelet), also known as black leaf streak. It was discovered in 1963 and named for its similarities with yellow Sigatoka, which ...

, an economically important pathogen of banana, is resistant to the

QoI Qo inhibitors (QoI), or quinone outside inhibitors, are a group of fungicides used in agriculture. Some of these fungicides are among the most popular in the world. QoI are chemical compounds which act at the quinol ''outer'' binding site of the ...

fungicides, due to a single

nucleotide Nucleotides are Organic compound, organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both o ...

change resulting in the replacement of one

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...

(glycine) by another (alanine) in the target protein of the QoI fungicides,

cytochrome Cytochromes are redox-active proteins containing a heme, with a central iron (Fe) atom at its core, as a cofactor. They are involved in the electron transport chain and redox catalysis. They are classified according to the type of heme and its ...

b. It is presumed that this disrupts the binding of the fungicide to the protein, rendering the fungicide ineffective. Upregulation of target genes can also render the fungicide ineffective. This is seen in DMI-resistant strains of ''

Venturia inaequalis ''Venturia inaequalis'' is an ascomycota, ascomycete fungus that causes the apple scab disease. Systematics ''Venturia inaequalis'' anamorphs have been described under the names ''Fusicladium dendriticum'' and ''Spilocaea pomi''. Whether ''V. in ...

''. Resistance to fungicides can also be developed by efficient efflux of the fungicide out of the cell. ''

Septoria tritici ''Zymoseptoria tritici'', synonyms ''Septoria tritici'', ''Mycosphaerella graminicola'', is a species of filamentous fungus, an ascomycete in the family '' Mycosphaerellaceae''. It is a wheat plant pathogen causing septoria leaf blotch that is ...

'' has developed multiple drug resistance using this mechanism. The pathogen had five ABC-type transporters with overlapping

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (aquatic environment), the earthy material that exi ...

specificities that together work to pump toxic chemicals out of the cell. In addition to the mechanisms outlined above, fungi may also develop

metabolic pathway In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell (biology), cell. The reactants, products, and Metabolic intermediate, intermediates of an enzymatic reaction are known as metabolites, which are ...

s that circumvent the target protein, or acquire

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

s that enable the metabolism of the fungicide to a harmless substance. Fungicides that are at risk of losing their potency due to resistance include ''

Strobilurins Strobilurins are a group of natural products and their synthetic analogs. A number of strobilurins are used in agriculture as fungicides. They are part of the larger group of QIs (Quinone outside Inhibitors), which act to inhibit the respiratory ch ...

'' such as

Fungicide resistance management

Cross-resistance can occur because the active ingredients share a common mode of action. The industry-sponsored Fungicide Resistance Action Committee (FRAC), whose parent organization is

CropLife International CropLife International is an international trade association of agrochemical companies founded in 2001. It was previously known as ''Global Crop Protection Federation'' and started out as ''International Group of National Associations of Manufact ...

, advises on the use of fungicides in crop protection and classifies the available compounds according to their chemical structures and

mechanism of action In pharmacology, the term mechanism of action (MOA) refers to the specific biochemical Drug interaction, interaction through which a Medication, drug substance produces its pharmacological effect. A mechanism of action usually includes mention o ...

so as to manage the risks of resistance developing. The 2024 FRAC poster of fungicides includes all the chemicals mentioned in this article.

Safety

Fungicides pose risks for humans. Fungicide residues have been found on food for human consumption, mostly from post-harvest treatments. Some fungicides are dangerous to human

health Health has a variety of definitions, which have been used for different purposes over time. In general, it refers to physical and emotional well-being, especially that associated with normal functioning of the human body, absent of disease, p ...

, such as

vinclozolin Vinclozolin (trade names Ronilan, Curalan, Vorlan, Touche) is a common dicarboximide fungicide used to control diseases, such as blights, rots and molds in vineyards, and on fruits and vegetables such as raspberries, lettuce, kiwi, snap beans, a ...

, which has now been removed from use.

Ziram Zinc dimethyldithiocarbamate is a coordination complex of zinc with dimethyldithiocarbamate. It is a pale yellow solid that is used as a fungicide, the sulfur vulcanization of rubber, and other industrial applications. Applications Known as ziram ...

is also a fungicide that is toxic to humans with long-term exposure, and fatal if ingested.National Center for Biotechnology Information. PubChem Compound Database; CID=8722, https://pubchem.ncbi.nlm.nih.gov/compound/8722 (accessed Jan. 13, 2019) A number of fungicides are also used in human health care.

References

External links

Fungicide Resistance Action CommitteeFungicide Resistance Action Group
United Kingdom

- National Pesticide Information Center, Oregon State University, United States {{Authority control Mycology Biocides