Fungicide

Key takeaways

Fungicide belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Fungicide to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Fungicide from memory before moving on to harder problems.

Reference excerpt

Fungicides are pesticides used to kill parasitic fungi or their spores. Fungi can cause serious damage in agriculture, 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, which are not taxonomically/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 (such as powdery mildew), basidiomycetes (various rust fungi), deuteromycetes (such as anthracnose), and oomycetes (such as downy mildew).

Types of fungicides

Like other pesticides, fungicides are numerous and diverse. This complexity has led to diverse schemes for classifying fungicides. Classifications are based on inorganic (elemental sulfur and copper salts) vs organic, chemical structures (dithiocarbamates vs phthalimides), and, most successfully, mechanism of action (MOA). These respective classifications reflect the evolution of the underlying science.

Traditional

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, and the beneficial fungus Ulocladium oudemansii.

Nonspecific In the 1930s dithiocarbamate-based fungicides, the first organic compounds used for this purpose, became available. These include ferbam, ziram, zineb, maneb, and mancozeb. These compounds are non-specific and are thought to inhibit cysteine-based protease enzymes. Similarly nonspecific are N-substituted phthalimides. Members include captafol, captan, and folpet. Chlorothalonil is also non-specific.

Specific Specific fungicides target a particular biological process in the fungus.

Nucleic acid metabolism bupirimate metalaxyl

Cytoskeleton and motor proteins carbendazim pencycuron

Respiration Some fungicides target succinate dehydrogenase, a metabolically central enzyme. Fungi of the class Basidiomycetes were the initial focus of these fungicides. These fungi are active against cereals.

azoxystrobin binapacryl boscalid carboxin cyazofamid pydiflumetofen

Amino acid and protein synthesis blasticidin-S kasugamycin pyrimethanil

Signal transduction fludioxonil procymidone

Lipid synthesis / membrane integrity propamocarb pyrazophos tecnazene

Melanin synthesis in cell wall tricyclazole

Sterol biosynthesis in membranes fenpropimorph hexaconazole imazalil myclobutanil propiconazole

Cell wall biosynthesis dimethomorph polyoxins

Host plant defence induction acibenzolar fosetyl-Al phosphorous acid

Mycoviruses Some of the most common fungal crop pathogens are known to suffer from mycoviruses, 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 biocontrols/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 occurs, where resistance to one chemical class of fungicides increases sensitivity to a different chemical class of fungicides. This has been seen with carbendazim and diethofencarb. Also possible is resistance to two chemically different fungicides by separate mutation events. For example, Botrytis cinerea is resistant to both azoles and dicarboximide fungicides. A common mechanism for acquiring resistance is alteration of the target enzyme. For example, Black Sigatoka, an economically important pathogen of banana, is resistant to the QoI fungicides, due to a single nucleotide change resulting in the replacement of one amino acid (glycine) by another (alanine) in the target protein of the QoI fungicides, cytochrome 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. Resistance to fungicides can also be developed by efficient efflux of the fungicide out of the cell. Septoria tritici has developed multiple drug resistance using this mechanism. The pathogen had five ABC-type transporters with overlapping substrate specificities that together work to pump toxic chemicals out of the cell. In addition to the mechanisms outlined above, fungi may also develop metabolic pathways that circumvent the target protein, or acquire enzymes 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 such as azoxystrobin.

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, advises on the use of fungicides in crop protection and classifies the available compounds according to their chemical structures and mechanism of action so as to manage the risks of resistance developing. The 2024 FRAC poster of fungicides includes all the chemicals mentioned in this article.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Fungicide

Start with the simplest possible case. Write down what Fungicide claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Fungicide before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Fungicide ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Fungicide

In research: Fungicide appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Fungicide in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Fungicide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Biocides, Fungicides, Mycology, so understanding it makes those chapters shorter.
In everyday life: Look for Fungicide outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Fungicide in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Fungicide means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Fungicide out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Fungicide in simple terms?

Fungicides are pesticides used to kill parasitic fungi or their spores. Fungi can cause serious damage in agriculture, resulting in losses of yield and quality.

Why does Fungicide matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Fungicide?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Fungicide.