Of the many modern means and methods of plant protection, the chemical method is of greatest importance - the use of chemical compounds that destroy harmful organisms. The chemical method is also effective for protecting various materials and products from them from biological destruction.

Chemicals used to kill various types of pests or to prevent their development are called pesticides .

In recent years, progesticides have been used - substances that do not have pesticidal properties, but are able to turn pesticides in the body of harmful insects or in other harmful organisms. Propesticides also include substances with pesticidal properties, which in the body to be destroyed are converted into more active compounds.

Depending on which harmful organisms pesticides act on, they are divided into the following main groups.

Acaricides — for tick control.

Algicides - for the destruction of algae and other aquatic plants.

Antiseptics - for the protection of metallic and nonmetallic materials from destruction by microorganisms. The same group includes drugs used for disinfection in order to destroy microorganisms pathogenic for humans and animals.

Arboricides — to destroy unwanted woody and shrubbery vegetation.

Aphids - to fight aphids.

Bactericides - to fight bacteria, pathogens of bacterial diseases of plants, animals and humans.

Herbicides — for weed control. In most cases, herbicides also include arboricides and algaecides.

Zoocides - to control rodents. In foreign literature, this group of substances is often called rodenticides or raticides.

Insecticides - to control harmful insects. Separate groups of insecticides have more special names, for example, acids.

Limacids, or molluscocides, to combat various mollusks, including gastropods.

Nematocides - to combat roundworms (nematodes).

Fungicides — to combat diseases and phytopathogenic fungi — pathogens of plants. Some fungicides can be used as antiseptics.

Pesticides also include

plant growth regulators — chemical agents of stimulation and inhibition ( retardants ) of plant growth,

preparations for removing leaves ( defoliants ) and drying plants ( desiccants ), used to facilitate the laborious work of harvesting cotton, soy, potatoes and many other crops;

preparations for repelling ( repellents ), attracting ( attractants ) and sterilization ( sex sterilizers) insects.

Drugs are being developed that repel insects from food - antifidings , or antifidants .

Herbicides, insecticides, fungicides, as well as plant growth regulators are most widely used in various sectors of the economy.

Depending on the ability to penetrate the pest, on the nature and mechanism of action on it, and some other criteria, these pesticides are divided into various subgroups.

According to the nature of the effect on plants, herbicides are divided into two main subgroups: continuous action , affecting all types of plants, and selective (selective) , dangerous only for certain types of plants and safe for others. This division is conditional, since the same substances, depending on the applied concentrations and consumption rates, can exhibit both continuous and selective action.

According to external signs of action and application features (introduction to the roots through the soil, application to the plant surface, etc.), herbicides are divided into three subgroups : contact, systemic and acting on the root system of plants or on germinating seeds.

Contact herbicides include substances that affect the leaves and stems of plants in direct contact with the drug. As a result of a violation of the normal processes of plant life, it dies. It should be borne in mind that such herbicides affect only those areas on which the drug fell, and the growth of new shoots and the further development of the affected plant are possible. By the nature of the action, defoliants and desiccants approach contact action herbicides. In many cases, contact herbicides are used as defoliants and desiccants if they are safe for the seeds of the crop being cultivated.

Systemic herbicides include substances that can move along the vascular system of plants. Such herbicides, once on the leaves and roots of a plant, spread rapidly throughout the plant, causing its death. The use of systemic drugs is especially effective in controlling weeds that have a powerful root system, especially perennial ones.

The third subgroup consists of herbicides, which are applied to the soil to destroy seeds, including germinating, and weed roots.

Insecticides by the nature of the penetration and damage of the insect organism are divided into the following main subgroups:

contact - affecting insects in contact with any part of the body,

intestinal - entering the body of an insect with food and poisoning it when poison enters the intestine,

systemic - able to move around the vascular system of the plant and poison insects as a result of eating poisoned plants,

and fumigants - penetrating the body of an insect through the respiratory system.

Most of the used insecticides can penetrate into the insect organism in various ways, in connection with this, certain drugs are assigned to one or another subgroup, given the main route of their penetration into the insect organism. For example, phosphamide is usually considered a systemic insecticide, although it has both a contact and a fumigation effect.

Some insecticides have a purely physical effect on the body, namely, they cause obstruction of the insect's respiratory tract, as a result of which it dies from asphyxiation. Such action can be exerted by mineral oils, finely divided silica gel.

Fungicides are usually divided into two main subgroups: fungicides for vegetative plants and seed dressers used for presowing treatment of seeds in order to protect seedlings from various diseases.

In turn, fungicides for vegetative plants are divided into prophylactic drugs (most often contact), used to protect plants from various infections, and eradicating drugs (healing) used to treat plants.

Among fungicides, there are contact and systemic drugs; the use of the latter gives a particularly good effect. To increase the efficiency and expand the spectrum of action, mixtures of systemic and contact fungicides are used.

An important group of pesticides is plant growth regulators , which have a wide range of purposes, in particular, drugs designed to accelerate ripening and fruiting, rooting during vegetative propagation by cuttings, to prevent freezing and drought, and to inhibit crop growth in the fight against lodging.

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