Repeated and systematic treatment of weeds with herbicides can give lasting results for the whole season. They are chemicals that adversely affect the development and growth of plants. Herbicides are used only against weeds.

In order to know which drug is better to treat weeds, you need to know the specifics of its action. The main distinguishing feature of such funds is their spectrum of action. All herbicides are divided into two groups: continuous action and selective.

Continuous action drugs

Those substances that are part of continuous herbicides are capable of destroying all vegetation that was at the time of spraying. Such radical drugs are used in areas where vegetation is contraindicated.

The action of herbicides of this type is divided into subgroups, namely:

• . contact preparations,
• . systemic,
• . soil.

Contact herbicides begin to act on the plant only when the drug has got on the leaves or stems. The leaves begin to turn yellow, wither and dry. All this leads to the complete destruction of the weed.

The use of soil herbicides is appropriate in cases where the weed has had time to pour its seeds into the ground. Such preparations are applied directly to the ground. They have a detrimental effect on weed seeds, thus preventing them from germinating.

Systemic herbicides are considered one of the most popular, as they quickly and effectively affect the development of the weed. When such a herbicide hits a weed, it not only attacks the outer sheaths, but is absorbed into the plant itself. It spreads throughout the weed, which means that its action is also aimed at destroying the root system.

Of course, systemic preparations are incomparable with soil herbicides. Systemic herbicides can have a complex effect on the plant, while soil herbicides can only affect the seeds.

Selective drugs

The second large group of herbicides is headed by drugs of selective action. These substances can destroy only certain types of weeds. When choosing such drugs, you must carefully read the instructions for use of herbicides. Often, it contains a complete list of weeds that can be adversely affected by the selected drug.

When buying selective herbicides, you need to know:

• . drug expiration date,
• . herbicide application rates
• . ways of application.

Can a herbicide harm a person? The instructions for herbicides always indicate the level of danger and toxicity to humans. All substances that are part of the selected drug have different degrees of toxicity.

The price of herbicides varies depending on the system of action. The average price of one liter of herbicide can be 200-5000 rubles per 1 liter.

Popular drugs

What herbicides are considered the most popular in the market of chemicals? The action of herbicides is directed against weeds that could have been permanent "residents" of any territory or plot for years. Therefore, the fight against them is considered one of the most difficult.

After reading dozens of reviews about herbicides, we can conclude about the most popular drugs that can really help radically:

Herbicide Roundup is considered a non-selective systemic drug. It has a wide range of effects, especially on perennial weeds. It is considered one of the most radical drugs in the world. The final destruction of the weed falls on 14-15 days after treatment.

Herbicide Tornado is aimed at systemic effects. It is used as a universal remedy for weeds. It contains an increased concentration of the main active substance.

Herbicide Prima is considered a powerful drug that has two active ingredients. Often it is used to control weeds that grow in areas with cereals and corn.

Herbicide Gold is applied against cereal monocotyledonous and dicotyledonous weeds. It is used in fields with corn, rapeseed, sunflower, soybeans, etc.

Herbicide Hurricane is a systemic preparation that can be used both in fields and on private land plots. It shows itself perfectly among vineyards, forest plantations, orchards and fields. It has a wide field of action, therefore it is considered a universal remedy.

Herbicide Stomp is used to control weeds in vegetable beds. It is considered a dual-action herbicide, as it can act systemically on the weed and destroy seeds through the soil.

Herbicide Titus is a post-emergence preparation that is used to control weeds in areas where tomatoes, potatoes and corn will be planted. It is considered a systemic drug. It is popular for its low application rate, high selectivity and long-term efficiency.

Herbicide Zenkor is designed for systemic exposure to the weed. The drug has a wide spectrum of action. Differs in the long period of protection. Controls annual dicotyledonous weeds.

Herbicide Eurolighting - post-emergence preparation. It is aimed at the destruction of cereals and dicotyledonous weeds. It acts both through the vascular system of the plant and through the soil. One treatment will be enough to keep the soil clean throughout the growing season.

Herbicide Granstar is used for weed control for barley, wheat, sorghum, soybeans, rapeseed. Has a wide range of effects. It perfectly destroys dicotyledonous weeds, as it affects systemically.

The herbicide Gezagard is distinguished by a rather long period of exposure - 10-12 days. It is used for potatoes, vegetable crops, corn, coriander, sunflower, grain crops. Not phytotoxic.

According to the chemical composition, herbicides are divided into two groups: inorganic and organic. The inorganic ones include: sodium nitrate (NaN03); sodium arsenite (Na3As03 - NaAsO2); sodium borate (NaB407 10H20); sulfuric acid and its compounds (H2SO4 and CuSO4); ammonium sulfamate (NH4S03 NH2); sodium thiocyanate (NaCNS); sodium chlorate; potassium cyanate (KCN03); calcium cyanamide (CaCN2). The organic group includes 2,4-dichlorophenoxyacetic acid (2,4-D); 2-methyl-chlorophenoxyacetic acid (2M-4X); 2-methyl-4,6-dinitrophenol (DNOC); 2,4-dinitro-6-sec-butylphenol (DNBF, butafen); pentachlorophenol; isopropyl-N-(3-chlorophenyl) - carbamate (chloroIFK) phenylisopropylcarbamate (IFK), etc.

The vast majority of herbicides currently in use are organic compounds.

According to the effect on plants, herbicides are divided into general and selective. The former are able to kill all plants (weeds and cultivated). They can be applied before sowing or planting, after sowing (planting) but before crops emerge, in gardens, nurseries, along roadsides and in the control of unwanted shrubs.

Selective herbicides are much more common. They destroy plants of some species, but do not have a negative effect on plants of other species. These properties of herbicides make it possible to control weeds during the growing season of crops.

It should be noted that the selective effect of herbicides of this group is manifested only when they are used in small doses. Higher doses affect all plants. Herbicides of general extermination and selective action are divided into contact (local action) and systemic (moving). Contact herbicides are those that destroy plant tissues in places of direct contact. They almost do not move around the plant, therefore, the death of weeds in crops will largely depend on the degree of wetting. When crops are treated with contact herbicides, only the aerial part of weeds is destroyed. Their underground organs remain unaffected, and many perennial weeds grow back.

Contact herbicides of selective action include: dinitroorthocresol (DNOC), dinitroorthotorbutylphenol (DNBF), pentachlorophenol (PCP), nitrafen (preparation No. 125), kerosene, etc.

The group of systemic herbicides includes herbicides that quickly move from the place of application throughout the plant. Entering its organs, they disrupt the metabolism and lead the plant to complete death. Systemic herbicides are very effective in controlling root and rhizomatous weeds. These herbicides include: derivatives of phenoxyacetic acid (2,4-D, 2M-4X, 2,4,5T), phenoxybutyric acid (2M-4XM, etc.), urea (monuron, fenuron, diuron), triazine (simazine, atrazine, IPA, chlorIFK, etc.) and representatives of groups with different chemical structure (2,3,6-TB, THA, dalapon, alipur, endothal, murbetol).

According to the nature of their entry into plants, herbicides are divided into leaf action (contact and systemic) and root action (soil). The former penetrate plants better and affect them more when applied to leaves than to other organs. Root action herbicides enter plants more intensively through the root system. Such herbicides include simazine, monouron, avadex, chlorIFK, dalapon, endothal, 2,4-DES, HDEC, etc.

According to the rate of damage and death of weeds, herbicides are divided into two groups: fast-acting (acutely toxic) and slow-acting (chronic toxicity). The first group includes contact preparations.

From herbicides of chronic toxicity, weeds die off gradually, their complete death sometimes occurs after a few months.

Herbicides is a collective name generally accepted in world practice for chemical plant protection products, consisting of the roots of two words - herb - a plant and cide - to destroy. The semantic translation of the definition is means that destroy plants.

The first methods of weed control were mechanical and consisted of carefully preparing the soil for sowing and selecting weed seeds from the seed. However, the detrimental effect of certain chemical compounds and their mixtures on plants has been known for a very long time.

Herbicides are classified according to the following criteria:

• by chemical composition Herbicides are divided into organic and inorganic. However, in agriculture, mainly organic herbicides are currently used.
• according to the principle of action on plants, (i.e. according to phytotoxicity) distinguish herbicides continuous(general fighter) and electoral(selective) actions. When the soil or vegetative plants are treated with herbicides of continuous action, the destruction of all vegetation is observed. Preparations of this group are not recommended for use in crops of cultivated plants. They are used mainly for the destruction of unwanted vegetation along canals, field roadsides and non-agricultural lands (right of way of railways and highways, etc.)
• according to the nature of the effect on plants herbicides are also divided into contact and systemic action. Contact herbicides (DNOC, sodium pentachlorophenolate, reglolon, mineral oils, etc.) have an effect only on those parts of the plant on which they fall. These drugs do not move in plants. Systemic herbicides (2,4-D, 2M-4X, atrazine, simazine, THA-trichloroacetate, banvel, suffix) can penetrate and move in plant organs. Moreover, most of these drugs have electoral action, those. destroy some types of plants and do not damage others.
• in relation to botanical classes of plants organic herbicides systemic action divided into groups: Antidicotyledons. These include 2,4-D, 2M-4X. These compounds are used to control broad-leaved (double-leaved) weeds in monocotyledonous (cereal) crops. Anticereal. Herbicides of this group suppress monocotyledons, and at optimal rates do not damage dicotyledonous plants. These include sodium trichloroacetate, dichloralurea, dalapon, etc. Herbicides of this group are used to kill grass weeds, mainly in crops of broad-leaved crops - sugar beet, sunflower, etc.
• by ways of making herbicides are divided into two groups: Soil preparations (diuron, prometrin, propazin, simazin, tillam, eptam, etc.). They are introduced into the soil without subsequent incorporation or with incorporation by a harrow or cultivator. Volatile herbicides (ronit, tillam, treflan, eptam, etc.) require immediate (no more than 10-15 minutes) incorporation into the soil, as they quickly evaporate or decompose in the light without coming into contact with the soil. They are applied dry (granulated) or by spraying the soil. Preparations used for the destruction of vegetative weeds (2,4-D, 2,4-DM, 2M-4X, 2M-4XM, betanal, carbin, reglon, etc.) They are used only by spraying plants.
• by the timing of the introduction The following four groups of herbicides are distinguished. Preparations used before sowing cultivated plants (in autumn or spring). Preparations used simultaneously with the sowing of cultivated plants. (local-tape (row) application). Preparations used immediately or shortly after sowing of cultivated plants, but before the emergence of their seedlings (for 3-4 days). Preparations used at the beginning of the growing season of weeds and cultivated plants.

Timing of herbicide application

Depending on the physicochemical properties of herbicides, environmental conditions and biological characteristics of cultivated and weed plants, the following terms for applying herbicides are distinguished:

post-harvest period- when preparing the site for next year in the fight against particularly malicious perennial weeds, which are more difficult to destroy in the spring of next year. At the same time, it is important that the preparations do not have a negative aftereffect on spring crops.

Before sowing (planting), i.e. pre-sowing application– in the spring before harrowing or for soil cultivation, i.e. before sowing spring crops. Soil herbicides are mainly used to control weeds emerging from seeds.

During sowing - pre-sowing- Simultaneously with the sowing of spring tilled crops. Soil herbicides are mainly used with a small incorporation into the soil, usually with a tape method of their application (in one unit with a seeder).

Post-sowing– immediately after sowing spring crops with immediate incorporation of soil herbicide by harrowing.

preemergence- 2-4 days before the emergence of spring crops with subsequent harrowing of the soil (in dry areas) or without it (in humid areas).

Post-emergence- at the beginning of the growing season of cultivated plants and the mass appearance of weeds, as well as on clean fallows in order to replace the mechanical tillage of the chemical and on uncultivated lands in the presence of especially malicious weeds.

Plant susceptibility to herbicides

Cultivated and weed plants have different sensitivity to herbicides due to their selective action. For each crop, only such a herbicide is recommended, to which the plants are resistant, and the weeds that clog its crops are sensitive to this drug. Those. in this case we are talking about the selective action of herbicides.

We have already said that the selectivity of herbicides can be biochemical and anatomical and morphological. Thus, triazine derivatives (atrazine, promethrin, etc.) are characterized by biochemical selectivity. They inhibit the processes of photosynthesis and transpiration in susceptible plants, as well as other biochemical processes leading to plant death.

Preparations have anatomical and morphological selectivity. These 2,4-D and 2M-4X herbicides, falling on the broad leaves of dicotyledonous plants, are well retained on them and penetrate into the aboveground, and then into the underground organs of plants, leading to their death. At the same time, these drugs, falling on the narrow leaves of cereal plants, located more or less vertically and covered with a wax layer of the cuticle, are weakly retained on the surface of these plants and practically do not damage them.

Weeds in different phases of growth and development also have different sensitivity to herbicides. Therefore, for the introduction of chemicals, a period is used when cultivated plants have the greatest resistance, and weeds have the least.

With the growth of weeds, the sensitivity of most of them to herbicides weakens. Young plants, which have tender covers and are characterized by rapid development and intensive metabolism, are damaged by herbicides to a greater extent than old ones. However, some perennial root weeds are more sensitive, for example, to the herbicide 2,4-D in the phase in the rosette phase than in the stem phase - the beginning of budding.

This is explained by the fact that in the rosette phase, perennial weeds have large reserves of nutrients in their roots, which increases their resistance to this herbicide. In addition, at later phases of growth and development in weeds, the outflow of plastic substances from leaves to other organs increases, and with increased foliage, more drug gets per unit of their surface than in the early stages.

Environmental conditions largely determine the sensitivity of plants to herbicides. Cultivated and weed plants are most sensitive to herbicides during the period when weather conditions are favorable for their growth and development.

Most herbicides used during the growing season are most toxic to plants at a temperature of 18-24 o C. They have a weak effect on weeds at 25-30 o C, when there is a low relative humidity of the air and have almost no effect on them at a temperature of 8 -10 o C. At a temperature of 18-24 o C, the effect of the herbicide on the plant appears already on the day of spraying, and at 10-14 o C - a little later. The new drug Satis is successfully used at +5 o C.

In this regard, on hot days, spraying is best done in the morning and evening hours, and on cold days, during the day, when the weather is most favorable for the manifestation of herbicide phytotoxicity.

The form of the preparation has a great influence on the effectiveness of the herbicide. In the event of even small precipitation, soon after spraying the crops with 2,4-D herbicide, its drops are washed off the leaves and the drug does not have time to act on the plants. Under these conditions, the advantage is esters 2,4-D, which are faster ( after 3-4 hours) penetrate into tissues than the amine salt 2,4-D (after 5-6 hours), and the signs of toxicosis in weeds do not decrease.

In contact with

Today, in agriculture, from the point of view of economic feasibility, it is quite profitable to use herbicides against weeds. With their help, weeds are destroyed in the crops, while the cultivated useful crops are not exposed to the harmful effects of destroying chemicals (subject to the optimal doses of application).

At its core, herbicides are organic and inorganic compounds. They have the ability to quickly penetrate into the tissues and cells of weeds, which leads to their death. These chemicals, depending on their species, can affect different parts of plants. Some of them get deep into the structure through the root, others - through the surface of the leaves.

Thus, herbicides for the destruction of weeds are one of the topical agrochemical means today.

Types of herbicides

291 herbicides are approved for use in agriculture. All of them are classified according to various indicators. This takes into account the chemical composition of the drug, and the effect on the plant. Important parameters are the timing of application, as well as the method of applying herbicides. In order for their use to be effective, all these tools are systematized into groups. The division into types of herbicides helps to purposefully choose the drug that is needed at a certain stage or in the fight against a certain weed.

However, if we talk about these chemicals in a broad sense, then they are used not only to combat unwanted vegetation. Depending on the objects that they must destroy and the targets, 3 large groups of substances are distinguished:

1) Actually herbicides. They are used in agriculture for the destruction of weeds.

2) Arboricides. These drugs are designed to eradicate shrubs and trees.

3) Algicides. Means that perfectly cope with aquatic vegetation. They are often used to clean water bodies.

Some of the drugs can cope with several tasks at once, are effective in several directions.

Chemical composition of herbicides

These substances are a variety of chemical compounds. All drugs are divided into two large groups: inorganic and organic herbicides.

Inorganic compounds include magnesium chlorate, ammonium sulfamanate, calcium cyanamide, and several other substances.

The group of organic herbicides is much richer and more diverse. It includes:

1) Benzonitriles. For example, Ioksinil.
2) Substituted phenols. Like DNOC.
3) Carbamates. This species includes Karbin, IFC.
4) Amides. Among the best known are Diphenamide, Solan.
5) Triazines. These include Propazin, Simazin, Prometrin.
6) Derivatives of urea. Here you can highlight Meturin, Kotoran, Fenuron.
7) Derivatives of uracil. The main one is Lenacil.

At the heart of one of the characteristics of all these herbicides is the classification according to the spectrum of action. These drugs can destroy all plants or only parts of them, so they are divided into continuous or selective action.

Continuous herbicides

In agriculture, they are often called general exterminators. They have a detrimental effect on any plants: both weeds and cultivated. Most often, solid herbicides are applied to the soil when they want to get rid of severe weeds on uncultivated lands. For example, it is advisable to use them for processing the adjacent territories of stadiums, roadsides, irrigation canals. One such drug is Imazapir.

But there are continuous herbicides that can quickly decompose. They can also be used on cultivated plantations. For example, on busy fallows (after harvesting fallow-occupying crops) or during the stubble period. They help a lot in the fight against perennials.

Sometimes such preparations are used in vineyards, orchards, and also to protect against weeds those crops that are considered tilled crops and have a row spacing of at least 70 cm.

Almost all inorganic compounds belong to herbicides of continuous action. This group also includes a number of organic substances: Glifogan, Roundal, Arsenal.

Among the most common drugs that destroy all plants are:

1) Glyphosate.
It copes well with weedy cereal annuals and perennials, as well as dicotyledons. Its action is aimed at inhibiting amino acids, as a result of which the unwanted plants treated with it die. The herbicide Glyphosate is often used in tea plantations and for processing in citrus and orchards. It can be used in the spring when unwanted plants are actively growing, or in the fall after harvest.

2) Diquat.
It is used to control weeds in potato and carrot crops. For this purpose, it is applied in the spring before the emergence of seedlings of useful crops. Diquat can also act as a desiccant (a substance that promotes the drying of plants). As such, it is often used immediately before harvesting alfalfa, sunflower, clover.

Selective herbicides

Their other agrochemical name is selective herbicides. The peculiarity of these drugs is that they are able to infect some plants without causing any harm to others, even if both species are in close contact with each other. In modern agriculture, most of these substances are used. You can use them in various ways. It can be spraying or root application.

The very first herbicide of selective action is considered to be copper sulfate. Laboratory studies have shown that this salt has an adverse effect on the development of dicotyledonous weeds.

Sulfonylureas, as well as those herbicides that prevent the accumulation of fats, can be attributed to the same group. Such preparations are usually applied to the leaves of weeds.

But substances based on trifluralin are usually applied to the soil. They are used for the destruction of dicotyledonous and cereal weeds. Often used to protect tomatoes, carrots, cabbage, cucumbers.

All selective herbicides are divided into 2 large groups:

1) Widely selective.
They can destroy various types of weeds. For example, preparations based on triazine, which do an excellent job with both dicotyledonous and monocotyledonous plants.

2) Narrowly selective.
Preparations aimed at the destruction of a certain type of plant. So, the herbicide Grodil is used to treat crops of barley and wheat. He will easily destroy the tenacious bedstraw. Tristar will help get rid of chicken millet, tubers, barnyard grass on rice plantations.

Classification by processing time

In crop production, the use of herbicides is effective only if they are processed at the appropriate time. Depending on this, all drugs are divided into 4 large groups:

1) Applied in autumn or spring before sowing crops.
2) Used together with sowing plants.
3) Applied after sowing 3-4 days before germination.
4) Applied at the very beginning of the growing season.

In this regard, two more types of herbicides are distinguished: soil and leaf.

soil herbicides

Such substances have different characteristics. Some of them are volatile, so they require mandatory sealing. Secondly, you can simply apply it to the top layer of the soil, and thus, soil herbicides create a kind of protective screen. Once the weeds reach it, they die because the soil herbicides are absorbed. Before such preparations, various parts of plants are vulnerable: seeds, roots, seedlings.

In order for the introduction of the substance to give the expected result, it is necessary to pay attention to the following aspects:

1) The structure of the soil. It is desirable that the soil clods be as small as possible. Then we can talk about a uniform distribution of the funds used.

2) Soil moisture. If the soil is dry, then the herbicides lose their effectiveness.

3) The consumption rate of the substance. For soil preparations, this is very important, besides, shallow incorporation into the soil (up to 5 cm) also increases the efficiency.

4) Soil type. Sandstones are characterized by a low content of humus, therefore they are classified as light soils. Herbicides can be used on them in a minimal amount. Lands rich in organic compounds, where the humus content exceeds 6%, are classified as heavy soils. Therefore, the dose of the drug should be increased. Otherwise, it may lose activity.

5) Weather conditions. At low temperatures or drought, the effectiveness of herbicide treatment is significantly reduced.

The most famous soil preparations include Harnes for corn and Stefacil for beets.

foliar herbicides

These types of agrochemistry are post-emergence preparations. They are applied during the growing season and absorbed by the above ground parts of plants, mainly leaves. Having penetrated into the weed, the leaf herbicide effectively blocks all important life processes, which leads to the death of the plant.

All types of foliar herbicides are widely selective preparations. That is, they have a negative impact on most of the weeds, and not just on a certain group.

As for the dosage, it is not fundamental for foliar herbicides. You can reduce the rate, but the tool will still cope with the task - it will prevent the formation of seeds or reduce their germination.

Today, preparations based on glyphosate are often used - Accord, Glycel, Forsat.

Contact and system

Depending on how herbicides act on plants, there are 2 more groups:

1) Contact.
Such substances damage only those parts of the weeds with which they come into contact. The rest remain unchanged. So, for example, when using foliar herbicides, the roots of perennials may not be affected. Therefore, it is important to pay attention to the thoroughness of the coating with the solution and the uniformity of its application. This group includes Bazagran, Acet, Betanes.

2) Systemic herbicides.
Able to penetrate deep into the structure, spreading, leading to damage to the plant. Especially effective for weed control with a strong root system. Here you can highlight Glyphosate, Buran, Roundal.

Classification by mechanism of action

Once in the vegetation, different herbicides affect the plant in different ways. Experts note the following drugs:

1) Destroying cell membranes (definyl ethers, bipyridyls). They act instantly, within a few hours. The plant dries up.

2) Suppressing the formation of amino acids (sulfonylurea and others). There is a lack of proteins in the plant, which blocks its growth. The result can be seen in a few days.

3) Hormone replacement (benzoic, pyridinecarboxylic acids). This type of herbicide depletes plants. Particularly effective against dicotyledonous weeds, their movement in cereals is difficult.

4) Fat inhibitors (benzofurans). Growth stops almost immediately, death occurs after 2 weeks.

5) Suppressing photosynthesis (triazines, nitriles). Usually used against dicotyledons, less often for cereals.

6) Pigment inhibitors (clomazone, containing fluorine herbicides). The development of plants is suspended.

7) Suppressing cell division (chloroacetamides). The growth of shoots and roots slows down, nutrition is disturbed and the weed dies.

New types of herbicides are constantly emerging. Scientists are creating new drugs, modern technologies will improve old drugs, making them effective, and I want to believe, safer.

Herbicides - chemicals used to control weeds in crops (plantings) of cultivated plants, in meadows and pastures, as well as in non-agricultural areas (roadsides, water utilities).

At present, a large number of herbicides have been synthesized and produced. To systematize and effectively use them in agriculture, it is necessary to combine them into groups.

herbicides classify on the following grounds:

1) by chemical composition;

2) according to the principle of action on plants, (i.e. according to phytotoxicity);

3) by the nature of the effect on plants;

4) in relation to botanical classes of plants;

5) by methods of application;

6) by terms of introduction; etc.

There are other approaches to the classification of herbicides:

1) according to the spectrum of action on plants (broad-spectrum herbicides and narrow-spectrum herbicides; for example: carbine and triallat are used against wild oats in spring wheat and barley crops);

2) by the nature of penetration into plants (for example, penetrating through leaves and aboveground organs; penetrating through roots);

9) according to the duration of the residual action.

Let's take a look at some of these classifications..

1) By chemical composition. Herbicides are divided into organic and inorganic. However, in agriculture, mainly organic herbicides are currently used.

2) According to phytotoxicity (i.e., according to the principle of action) distinguish continuous herbicides(general fighter) and electoral(selective) actions. When the soil or vegetative plants are treated with herbicides of continuous action, the destruction of all vegetation is observed. Preparations of this group are not recommended for use in crops of cultivated plants. They are used mainly for the destruction of unwanted vegetation along canals, field roadsides and non-agricultural lands (right of way of railways and highways, etc.)

To herbicides of continuous action include most inorganic compounds, as well as a number of organic substances (simazine, atrazine, sodium trichloroacetate, roudap, utal, dalapon, DNOC, etc.), which destroy at elevated rates even those plants to which they show selectivity at optimal rates.

herbicides electoral action destroy some types of plants and do not damage others. Moreover, among them herbicides stand out, which are distinguished by a narrow specialization in relation to the protected crop. For example, the suffix destroys wild oats in spring wheat crops. Most selective herbicides are used to control weeds in crops of several crops. Thus, amine salt 2,4-D is used in crops of grain crops, corn, perennial grasses, hayfields and pastures, fallows and individual essential oil crops (rose, lavender).

Selectivity of herbicide action defined:

primarily:

chemical composition;

Form of preparation (powder, aqueous solution, soluble wettable powder, emulsion concentrate, granular preparation, mineral oil suspension);

The norms of the drug;

Terms and methods of spraying crops;

growth phases;

Physiological and biochemical characteristics of cultivated and weed plants;

Anatomical and morphological features of cultivated and weed plants;

The conditions of the external environment.

The selectivity of the action of herbicides can be manifested both by one of the named signs, and by their complex.

Factors determining the selectivity of the herbicide action:

Physical (dose, formulation, method of application);

Biological (morphological, physiological and metabolic features - the area of ​​the leaf blade);

Chemical properties of herbicides: molecular composition, solubility, volatility, adsorption properties;

The use of antidotes together with herbicides (increases the resistance of cultivated plants);

The possibility of combining herbicides with other pesticides and fertilizers (the use of herbicides with mineral fertilizers increases the herbicidal activity and resistance of agricultural plants to herbicides).

3) By the nature of the action on plants herbicides are also classified into a) contact and b) systemic action.

Contact herbicides(DNOC, sodium pentachlorophenolate, reglone, mineral oils, etc.) have an effect only on those parts of the plant on which they fall. These drugs do not move in plants.

Systemic herbicides(2,4-D, 2M-4X, atrazine, simazine, THA-trichloroacetate, banvel, suffix) can penetrate and move in plant organs. Moreover, most of these drugs have electoral action, those. destroy some types of plants and do not damage others.

4) In relation to the botanical classes of plants (systematic position) organic herbicides systemic action divided into groups:

Antidicotyledons. These include 2,4-D, 2M-4X. These compounds are used to control broad-leaved (double-leaved) weeds in monocotyledonous (cereal) crops.

Anticereal. Herbicides of this group suppress monocotyledons, and at optimal rates do not damage dicotyledonous plants. These include sodium trichloroacetate, dichloralurea, dalapon, etc. Herbicides of this group are used to kill grass weeds, mainly in crops of broad-leaved crops - sugar beet, sunflower, etc.

5) According to the method of application herbicides are divided into two groups:

Soil preparations (diuron, prometrin, propazin, simazin, tillam, eptam, etc.). They are introduced into the soil without subsequent incorporation or with incorporation by a harrow or cultivator. Volatile herbicides (ronit, tillam, treflan, eptam, etc.) require immediate (no more than 10-15 minutes) incorporation into the soil, as they quickly evaporate or decompose in the light without coming into contact with the soil. They are applied dry (granulated) or by spraying the soil.

2. Drugs used for destruction of vegetative weeds (2,4-D, 2,4-DM, 2M-4X, 2M-4XM, betanal, carbine, reglone, etc.) They are used only by spraying plants.

6) By the timing of the introduction The following four groups of herbicides are distinguished.

Preparations used before sowing cultivated plants (in autumn or spring).

Preparations used simultaneously with the sowing of cultivated plants. (local-tape (row) application).

Preparations used immediately or shortly after sowing of cultivated plants, but before the emergence of their seedlings (for 3-4 days).

Preparations used at the beginning of the growing season of weeds and cultivated plants.