What Are the Functions of Fungicides? A Full Breakdown of Their Main Effects and Uses
What are the functions of fungicides? Please explain. Fungicides work in two ways: first, protective fungicides, and second, systemic fungicides. Protective fungicides contact the pathogen directly outside or on the surface of the plant, killing or inhibiting the pathogen so that it cannot enter the plant, thereby protecting the plant from disease...
What are the functions of fungicides? Please explain.
Fungicides work in two ways: first, protective fungicides, and second, systemic fungicides.
Protective fungicides contact the pathogen directly outside or on the surface of the plant, killing or inhibiting the pathogen so that it cannot enter the plant, thereby protecting the plant from harm by the pathogen. Fungicides of this type are called protective fungicides, and their action has two aspects: first, after spraying, the fungicide contacts the pathogen and directly kills it, that is, "contact fungicidal action"; second, the fungicide is sprayed on the plant surface, and when the pathogen lands on the plant and contacts the fungicide, it is killed by the poison, which is called "residual fungicidal action."
Protective fungicides mainly include the following categories:
Sulfur and inorganic sulfur compounds, such as sulfur suspension concentrate and solid lime sulfur mixture; copper preparations, mainly Bordeaux mixture and copper-ammonia mixture; organic sulfur compounds, such as thiram, zineb, amobam and mancozeb; phthalimide types, such as captan, dichlofluanid and folpet; antibiotic types, such as validamycin, blasticidin and polyoxin; and other types, such as yekuling, yekujing, chlorothalonil and nuarimol.
Systemic fungicides, after being applied to a certain part of the crop, can be absorbed by the crop and transported within the plant to other parts where they take effect. Fungicides with this property are called "systemic fungicides." Systemic insecticides have two modes of translocation: first, acropetal translocation, meaning that after the fungicide is absorbed into the plant, it moves with the transpiration stream toward the top of the plant, reaching the top leaves, terminal buds, leaf types and leaf margins. Most current systemic fungicides belong to this category. The other is basipetal translocation, meaning that after the fungicide is absorbed by the plant, it travels downward within the phloem along the transport pathway of photosynthesis products.
Systemic fungicides mainly include the following categories:
Benzimidazole types, such as benomyl, carbendazim, thiabendazole, thiophanate and thiophanate-methyl; dicarboximide types, such as iprodione and vinclozolin; organophosphorus types, such as IBP, kitazin P and fosetyl-aluminium; phenylamide types, such as metalaxyl; and sterol biosynthesis inhibitor types, which include tridemorph, triforine, dimethirimol, ethirimol, imazalil and prochloraz, triadimenol and triadimefon, etc. In terms of chemical structure, they belong respectively to morpholine, pyrazine, pyridine, pyrimidine, imidazole and 1,2,4-triazole compounds. Sterol synthesis inhibitor fungicides have both protective and curative action and a relatively broad fungicidal spectrum.
The principles by which fungicides control plant diseases:
Simply put, a fungicide is a compound that has a toxic killing effect on pathogenic microorganisms. However, the term "fungicidal" is not limited to the two meanings of "killing" pathogenic microorganisms or inhibiting their growth or spore germination. Fungicides that can kill pathogenic microorganisms exert a fungicidal action, while fungicides that can inhibit the germination or growth of pathogen spores exert a fungistatic action, and both actions can achieve the goals of disease prevention and disease treatment in agricultural production. Fungicides differ in their mode of action and are used in different ways, but fundamentally, the principles by which fungicides control diseases come down to three: chemical protection, chemical treatment and chemical immunization.
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