What acid is included in herbicides? Continuous action herbicides for weed removal. Necessary natural conditions

Herbicide- a chemical plant protection product used to control weeds (mainly herbaceous).

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Herbicides are a collective name generally accepted in world practice. chemicals plant protection, consisting of the roots of two words - herb - plant and cide - destroy. The semantic translation of the definition is means that destroy plants. The term was coined around 1944.

Story

The first methods of controlling weeds were mechanical and consisted of carefully preparing the soil for sowing and selecting weed seeds from the seed material. However, the harmful effects of some chemical compounds and their mixtures on plants have been known for a very long time.

Antiquity

. In the 4th century BC. The ancient Greek naturalist Theophrastus proposed destroying tree growth by treating root system tree oils, in particular olive oil. In the poems of the Roman poet Virgil, belonging to the 1st century BC, it was said that plants die from sea water. (photo) This led to the emergence of a long-term “fashion” for using salt to kill plants. When the Romans conquered Carthage, they sprinkled salt on its fields, making the land barren.

Middle Ages

. In the Middle Ages, salt, slag and ash were used to control vegetation on roads and weeds in crops. Unfortunately, this often caused the simultaneous death of crop plants, so that the practice of using these herbicides remained very imperfect.

New time

. After studying the properties, the first selective herbicide was discovered: the ability of copper compounds (in particular, copper sulfate) to inhibit the growth of dicotyledonous weeds was noted. Also in 1897, Martin reported the herbicidal effect of ferrous sulfate, and Duclos mentioned the successful use of copper nitrate and sulfuric acid in weed control.

XX century

. In 1908, the American agronomist Bolly published data on the successful use of sodium chloride, ferrous sulfate, and sodium arsenite as means to get rid of weeds in wheat crops. In the Hawaiian Islands, sodium arsenite was also used to clear weeds from sugarcane plantations.

In Russia, salts and acids began to be used for plant protection also from the beginning of the 20th century. In 1932, I. Negodnov proposed using aviation to spray fields with herbicides. In the 30s, sodium chlorate, ferrous sulfate and acids began to be often used as herbicides, but aggressive solutions quickly rendered the equipment for their application unusable, so that over time they were abandoned.

In 1938, French researchers released the drug Synox, made from the sodium salt of 4,6-dinitro-ortho-cresol and intended for the treatment of flax crops, grains and some vegetables. At the same time, mineral oils began to be used in carrot crops, and Irwin discovered the herbicidal activity of 2-naphthoxyacetic acid.

After the discovery of the hormone-like compounds 2,4-D and 2,4,5-T in 1944, a new era began in agronomic chemistry.

In the USSR, particularly significant growth rates in the volume of herbicides used were observed in the 60-70s of the 20th century. Their use declined over the next decade. The irrational use of drugs has led to the emergence of resistance to them in weeds and to a decrease in the effectiveness of treatments, which has forced us to limit the production and application of herbicides.

In 1982, a biological method of combating harmful plants was proposed in the USA. It consisted of using a drug based on a pathogenic fungus that can inhibit the vital activity of vetch. It was also proposed to use “natural enemies” of weeds as a means to eradicate unwanted vegetation. Potential candidates included: geese for weed control in cotton, grass carp for algae removal, bitter nematode against bitter grass, etc. Unfortunately, it turned out that the costs of such methods of control are prohibitively high; using herbicides is many times cheaper.

Mistakes and tragedies in the history of herbicides

. Illiterate use of salts and acids suppresses not only harmful, but also cultivated plants, and also leads to sterilization of the soil: the death of beneficial flora and insects. The presence of arsenic compounds in the soil causes poisoning among people. But none of this can compare with the famous episode in history when herbicides were used as chemical weapons.

During the Vietnam War, the US government used a mixture of substances called Agent Orange (2,4,5-trichlorophenoxyacetic acid and 2,4-dichlorophenoxyacetic acid + toxic intermediates of their synthesis) as a defoliant to spray in the jungle. Due to the presence of dioxins, the mixture had a teratogenic and carcinogenic effect, as a result of which both the Vietnamese population living in the area where the herbicides were treated and the American soldiers in the area where the drug was sprayed suffered. The use of chemical weapons resulted in the death of several hundred thousand people and the birth of children with hereditary diseases and genetic mutations. Victims of Operation Ranch Hand still live in Vietnam; (photo) They were denied compensation for damages.

In addition to Agent Orange, there were other herbicide formulations designed to destroy rice crops (Agent Blue) and other crops.

Classification of herbicides

By purpose

Drugs in this group can act not only on weeds. Depending on the purposes (types of objects destroyed), herbicides include:

Some drugs have a simultaneous effect in two or more directions.

According to the spectrum of action

Within each direction of action, herbicides are capable of destroying all plants or only part of them. Based on this, they are divided into two groups according to the spectrum of action:

By chemical structure

herbicides are divided into:

According to the ability to move around the plant

Based on this, herbicides are:

Methods of penetration and mechanism of action

Contact preparations are characterized by low mobility in plants, so they practically do not penetrate inside. Uptake of systemic herbicides occurs either through leaves or roots, depending mainly on the application method active substance.

Penetration

. Once on the surface of the leaf, the product can:

remain on the surface (ferrous sulfate);
dissolve in cuticle wax ( aromatic oils);
penetrate into the aqueous phase of epidermal cells (bromoxynil);
penetrate the phloem through the symplast (2,4-D).

When applied by roots, systemic herbicides adsorbed by root hairs and then move to the site of action with an acropetal flow of fluid.

Most modern herbicides act on plants through enzyme systems.

Depending on the mechanism of action

, means:

destroy cell membranes;
suppress the formation of amino acids;
exhibit hormone-like effects;
inhibit fat synthesis;
inhibit photosynthesis;
inhibit the formation of pigments;
inhibit meristematic mitosis.

Other, smaller drugs have different mechanisms of action: they disrupt auxin transport, suppress the formation of cellulose, or have unclear patterns of action on plants.

Destruction of cell membranes

Bipyridyls, triazolinones, diphenylethers.

After absorption by leaf tissues, free radicals are formed that have a damaging effect on cell membranes. Reactive oxygen species interact with fatty acid residues, and the lipid peroxidation reaction starts. The membranes are damaged, the contents of the cells move into the intercellular space. In the sun this process occurs faster. First, soaking occurs, and then necrosis and desiccation of the tissues. Symptoms of damage from these herbicides develop quickly, within a few hours.

Suppression of amino acid formation

Inhibition of the formation of amino acids leads to a lack of structural proteins in plants, which suppresses the processes of growth and development. Herbicides that inhibit amino acid synthesis act relatively slowly, the effect developing over several days.

Hormone-like drugs

Phenoxyacetic, quinolinecarboxylic, benzoic, pyridinecarboxylic acids.

They replace natural plant hormones and show their effect most effectively in dicotyledonous weeds growing in grain crops, because they move poorly in grains. Application is most justified in the initial stages of weed growth.

After absorption through roots and leaves, hormone-like herbicides have toxic effect on plants. The features of this action are not known for all herbicides. In some cases, under the influence of drugs, the process of ethylene formation is initiated, which causes inhibition of growth in the length of shoots or roots. At the same time, plant cells increase in size without having time to store nutrients. This leads to gradual depletion of the weed and causes death.

Inhibition of fat formation

Cyclohexanediones, benzofurans, aryloxyphenoxypropionates.

Suppress the formation of fatty acids, have high degree selectivity for annual and perennial grasses. They process vegetative parts of plants.

They move with the phloem current along the symplast to places of active growth. As a rule, they inhibit acetyl-coenzyme-A carboxylase, which is responsible for initial stages formation of fatty acid molecules. Due to disruption of their synthesis, the formation is secondarily inhibited cell membranes. As a result, plant growth stops almost immediately, and later other symptoms of damage appear; Weed death occurs after 10-14 days.

Suppression of photosynthesis

Suppression of pigment formation

Isoxazolidinones, cyclohexanediones, some fluorinated herbicides ().

They move more along the xylem, so they show their effect better when introduced into the soil. After penetration into the plant, they move into the chloroplast lamellae, where they suppress the formation of chlorophylls and carotenoids necessary for the process of photosynthesis. Carotenoids transfer light energy to chlorophyll and protect it from photo-oxidation, therefore, if their formation is disrupted, chlorophyll becomes discolored and loses its basic properties. Suppression of carotenoid synthesis can occur in different ways. For example, flurochloridone does this by inhibiting the enzyme phytoene desaturase, and benzoylcyclohexanediones inhibit the formation of pigments in the plant by inhibiting the enzyme 4 - hydroxyphenylpyruvate dioxygenase.

Isoxazolidinone clomazone harms weeds by inhibiting the formation of di- and tetraterpenes (precursors of gibberellins responsible for the development and growth of plants). Diterpenes are part of chlorophyll molecules, so inhibition of their formation also leads to a decrease in the formation of the latter.

Mitosis inhibition

Selectivity of herbicide action and plant resistance to these drugs

Effect of herbicides on sensitive plants

. Contact with a herbicide is always a stressful effect, since the plants have not previously interacted with such substances. In sensitive species, under the influence of a chemical preparation, they irreversibly change metabolic processes, harmful metabolic products accumulate, synthetic processes are inhibited, and all this leads to their death.

Effect of herbicides on resistant plants

. Along with a detrimental effect on some species (varieties), herbicides can stimulate growth processes in others (usually target crops). Initially, metabolic disorders also occur in them, accumulation of simple products(amino acids, sugars). However, all these changes are reversible and soon form a compensatory reaction. After more or less long period inhibition, recovery systems are stimulated, enzymes are activated, photosynthesis processes occur more fully, the susceptibility of fertilizers improves, and all together this contributes to increased growth and sometimes increased yield.

The degree of “danger” of herbicides for weeds, in addition to the peculiarities of the mechanism of action of the drug and other factors, is determined by the stability of the herbicide in the soil and on the surface of plants. (photo)

Areas of use of herbicides

The use of herbicides is not limited to agricultural interests. Non-selective drugs are used to treat areas around industrial facilities for various purposes and on communication routes (under power lines, on roads). At one time, they even found use in the work of the drug control service, when they were used to destroy discovered hemp plantations. (photo)

In addition, herbicides mixed with were used for military purposes to detect the location of the enemy in forests and jungles.

Use of herbicides in agriculture

Preparative forms

Herbicides are produced in the form of wettable powders, and.

Deadlines for depositing

According to the timing of application, herbicides are pre-emergence and post-emergence. Treatment with pre-emergence preparations can be carried out before, during or after sowing, and post-emergence preparations are applied simultaneously with the appearance of the first shoots, during plant tillering and when the weeds reach a certain height (5-15 cm).
As a rule, young plants are more inhibited by herbicides than older ones. Thus, when treating soybean seedlings 10, 20 and 30 days after the appearance of the first shoots, there was a decrease in yield by 9.9, 19.8 and 39.1%.

Methods of application

The method of application is determined by the intended contact of the herbicide with certain parts of the plants.

Foliar herbicides are used to control vegetative plants; they are applied to above-ground parts - shoots, leaves, etc. Application is usually done by spraying.
Soil herbicides are applied to moist soil and spread throughout it.
Root herbicides are applied by incorporation into the soil or by drip irrigation (fertigation).

Peculiarities

. If a non-selective herbicide is used, then cultivated plants should be protected from its action by carrying out a targeted herbicide. It is necessary to take into account changes in plant resistance to the action of drugs at different “ages”.

Necessary natural conditions

When applying herbicides to the soil, soil moisture is important. When dried, the drug remains in upper layers and has virtually no effect on plant roots, which reduces the effectiveness of the product. When substances are applied to above-ground parts of plants, in the next 2-4 hours before and after treatment they should not be washed off with water, that is, weather conditions should be assessed (presence of rain, expected precipitation, spring frosts).

Herbicides and crop rotation

The use of herbicides requires the evaluation of crop rotation parameters. Soil-resistant herbicides should not be used in areas where plants sensitive to these agents will be sown next season. For example, if potato crops are treated with trifluralin, winter grains cannot be planted in this field in the future. And vice versa: proper planning Alternating crops allows you to reduce the frequency of treatments.

Consumption rates

The correct determination of this indicator is extremely important, since if the norm is insufficient, the area will not be completely rid of weeds, and if the dose is exceeded per unit area, it can lead to the protected crops also being damaged. The establishment of the norm should be carried out in accordance with, but individually, taking into account the degree of infestation, the species composition of weeds, and the properties of the soil. Thus, preparations based on glyphosate, when treating fruit and vineyards, are used at a rate of 2-4 l/ha when infested with annual cereals and dicotyledonous weeds, but if the weeds include dicotyledonous and perennial cereals, it is used at a rate of 4-8 l/ha .

Before using herbicides, determine the degree of soil contamination with weeds, which is assessed by the number of weeds per 1 square meter area.

Herbicides and the environment

Every year, about 4.5 million tons of various herbicides are produced around the world, which are intensively applied to the soil. This cannot go unnoticed for the state of the environment in areas of developed agriculture.

First of all, these substances accumulate in the soil. They are able to be washed out of it, entering water bodies, and then into the body of animals and humans. The processes of physico-chemical absorption, biological and enzymatic destruction play a role in ridding the soil of poisons, but some of the action toxins can still penetrate into the crop and pose a threat to the quality of feed and food.

In addition, chemical components inhibit the vital activity of the biological component of the soil: bacteria, fungi, actinomycetes, algae, rhizomes, flagellates, etc. that live in it. All of them participate in the formation of humus, and their death inevitably leads to a deterioration in the nutritional properties of the soil. This is very important, since the effect of the applied drug can last quite a long time. long time. Moskvichev Yu. A., Feldblum V. Sh. Chemistry in our lives (products of organic synthesis and their application): Monograph. - Yaroslavl: YAGTU Publishing House, 2007. - 411 p.

Images (reworked):

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Kulikova N.A., Lebedeva G.F. Herbicides and environmental aspects of their use. Tutorial. - Moscow, book house "LIBROKOM", 2010. - 152 pp., Illustrations from the book

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Every gardener knows well how difficult it is to rid plantings of weeds. Unlike pests and diseases, the harm caused by weeds is indirect, but they significantly reduce the quality and quantity of the crop and make harvesting difficult, so herbicides are used to overcome the situation. These are chemicals that effectively help get rid of weeds without harming the quality of products and soil microorganisms.

Definition and classification of herbicides

Products that destroy vegetation are called herbicides. The name comes from the Latin words herba - grass and caedo - I kill.

In order not to get confused in the huge selection of herbicides synthesized in our time, they were divided into types. Herbicides are divided according to several indicators, namely:

By chemical components:

organic preparations do not harm nature and are harmless to the health of people and animals. They are used in agriculture;
inorganic compounds. Their use is limited due to a number of disadvantages. They are ineffective and unsafe for the health of living beings.

In terms of phytotoxicity, in other words, based on the effect on plants:

By the nature of the action:

contact herbicides are incapable of moving through plant organs and act only at the point of contact, causing burns and wilting;
systemic are capable of moving in plant organs, penetrating them and destroying them completely. Most of them are selective.

In relation to botanical classes, organic preparations systemic action divided into two groups:

By method of application:

By terms of deposit:

With such a broad classification of herbicides, it is very important in each specific case to choose the right drug and know how to apply it correctly.

Rules of application

First of all, herbicides are chemicals. Therefore, it is recommended to use them only when there are a lot of weeds on the site, and other methods of controlling them have proven ineffective.

Preventive measures using the drug are carried out in early spring, when the harmful effect on cultivated plants is minimal. Also, weeds are more susceptible to drugs at the beginning of the growing season.

Work is carried out in the absence of wind in the morning until 10 o'clock or in the evening after sunset, from approximately 18 o'clock. During these hours the air humidity is quite high. No work is carried out during rain. Processing efficiency is greatly influenced by temperature regime. Early spring The thermometer should not fall below 5 0 C. For application to the soil, the optimal air temperature should be 20−25 0 C.

Spray method

When using the spraying method, the necessary equipment is prepared for the process at home, and the sprayer is adjusted directly on the site. You also need to know that the toxicity indicator of a herbicide when spraying is not related to the amount of working fluid on well-wetted plants, but for poorly wetted plants it is advisable to increase the volume of working fluid. The consumption of the solution will be greater in hot weather due to the rapid evaporation of moisture. The working fluid is diluted immediately before use in a non-metallic container.

When using soil herbicides, long-term toxic effects of chemicals are ensured, and their effectiveness does not depend on external weather conditions. However, rain even favors the uniform distribution of the active substance in the soil. These chemicals can be applied by application to the soil surface or by post-incorporation and incorporation into the soil to a specific depth.

Work related to the use of fertilizers is carried out in special clothing - a robe, hat, boots and rubber gloves. For protection respiratory tract Respirators or masks are used, and goggles are used to protect the eyes.

Deadlines for depositing

Depending on environmental conditions, the range of cultivated plants and the types of weeds growing on the site, certain timing of herbicide application:

Preparations for the garden

For a summer cottage, it is best to choose selective-type drugs. For example, the modern selective herbicide “Lontrel” has proven itself well in strawberry growing areas and on lawns. This drug contains the substance clopyralid, which is close in class to vitamins. It disintegrates almost immediately in the soil without causing damage to it. Kills thistles, thistles, suppresses ragweed, dandelion, knotweed and does not affect the leaves of cultivated strawberries or the grasses of the lawn. Apply Lontrel as weeds emerge in warm weather. The drug is quickly destroyed in air and does not linger in the soil.

For lawns, it is even better than Lontrel to use the combined type drug Proweed. This post-emergence herbicide fights dicotyledonous weeds and can destroy more than 100 types of weeds within a few weeks, maximum 4 weeks. The drug has no aftereffect and is environmentally friendly, as it is used in minimal doses and quickly decomposes into its components.

Another effective herbicide is Glyphosate. Based on it, such drugs as Roundup, Tornado, Hurricane have been developed - at least 100 items in total. These drugs fight a huge number of weed species. When using them, it should be taken into account that the greatest effect is manifested when the weeds have already grown a good vegetative mass, therefore, when treating the crops with the drug, they need to be isolated, for example, by covering them with film.

The packaging of each chemical contains instructions for use, which should be read carefully before use.

To remove weeds manually or resort to the help of chemicals - every gardener or summer resident decides on his own. The use of herbicides without causing harm to the environment, soil and the health of people and animals is possible with a competent and reasonable approach.

If you translate the word, it comes from herb - “plant”, cide - “to destroy”. Depending on their mode of action, there are selective and continuous (non-selective) herbicides. In the article you will find information about continuous action herbicides and the features of their use.

General description

As the name implies, all green ones are destroyed in a continuous action, including. They, as a rule, act on greenery through contact, destroy the membrane and lead to necrosis or rapid death of vegetation.

Important! All herbicides pose a risk to human and animal health. In 2015, the International Agency for Research on Cancer classified glyphosate and 2,4-D as possible carcinogens. There are studies that claim the effect of anti-weed drugs on human DNA. About 290 herbicides are allowed to be used in agriculture.

Continuous herbicides are used less and less today; selective substances are becoming more popular. However, they are still actively used both in agriculture and at industrial sites, in construction, near airfields and railway tracks. In agriculture they are used both professionally, in large farms, and in small farms and summer cottages. By chemical composition herbicides are:

organic;
inorganic.

Depending on the period of use, continuous herbicides are divided into:

pre-emergence;
post-emergence;
universal, used in different periods vegetation development.

Depending on the specific application, there are herbicides:

soil (affect roots, seeds, seedlings);
leafy (affect the above-ground part of herbs).

Forms of release of herbicides:

aqueous solution;
granular composition;
powder mixture;
suspension.

Species

All anti-weed preparations are divided into 2 groups according to the method of action on herbs and method of application:

contact;
systemic.

Contact

Contact substances affect leaves and stems in direct contact with them. They disrupt the normal life processes of the grass and lead to its death. However, after their application, new shoots may grow as the roots remain unaffected.

The substances are resistant to moisture. They are used if it is necessary to quickly and massively destroy vegetation. Are particularly toxic, therefore, their use on private farms is prohibited.

System

Systemic substances penetrate into vascular system herbs and thus spread throughout all organs, provoking their rapid death. In this case, both aboveground and underground organs die.

Such continuous action herbicides are especially effective when treating weed plantations that have a powerful root system, as well as against

Features of selection and application

In order to choose the right drug, you need to clearly understand in which territory it will be used, against which ones, and what effect needs to be achieved.

In general, chemicals with a continuous systemic effect are suitable for use:

on agricultural areas - in fields during pre-sowing and post-harvest periods, in summer cottages;
in gardening - for processing row spacing, including on;
on non-agricultural lands - along runways, railway tracks, power lines, highways, highways, in city parks;
in shipping - to destroy objects that interfere with the passage of ships.

There are known facts in world history that chemicals were used as one of the military tactics to destroy enemy crops and deprive him of food or negative influence on the health of the nation.

Depending on the grass for which the chemical is intended, there are several ways to use it:

to get rid of annuals, as a rule, pre-sowing treatment is used, during and after harvesting;
perennials are exterminated by the post-harvest method or by periodically treating the areas between plants.

When using anti-weed chemicals, you must strictly adhere to the dosage recommended by the manufacturer, as well as recommendations on how to behave with chemicals.

Important! Since herbicides are toxic to the human body, they should be used using personal protective equipment. You need to work on calm days at temperatures of 16–25 °C. When working, you need to wear a protective suit that covers your body, protect your eyes with special goggles, and protect your respiratory tract- mask.

Consumption of food and drinks while using chemicals is strictly prohibited. You cannot work after drinking alcohol. After applying herbicides, you should take a shower, wash your hair and drink a glass of milk.

It must be remembered that herbicides are drugs that have a prolonged effect, so there is no need to rush with re-treatment. It is better to wait 2-3 weeks for the effect.

We should not forget that continuous action preparations also kill cultivated plants, so if the treatment is carried out during their growing season, you need to use a sprayer with a fine stream.

Continuous action herbicides (with description and photo)

The group of non-selective herbicides includes some organic matter(“Roundup”, “Glyfogan”, “Arsenal”), as well as almost all inorganic ones.

Let's look at the 10 most commonly used ones.

. A broad-spectrum drug. It is considered one of the best for sealing in industrial areas. Very good for processing virgin soil. The substance included in its composition can act on some plants for 4–5 years.
The peculiarity of this drug is that when used systemically in the phase of active plant growth and after the final harvest, the synthesis of amino acids slows down and, over time, completely stops. It is good for treating areas that should be completely destroyed. It is used in vineyards, tea fields, and citrus orchards.
- a relatively new continuous action herbicide. It has proven itself well in fields with monocot and perennial crops, as well as during the destruction. It is used in gardens, vineyards, industrial and urban facilities.
. Universal remedy, which, falling on the leaves of a plant, moves down it and, reaching the root system, kills it. Can be used over a wide temperature range. Suitable for use in a summer cottage.
- a continuous action herbicide, which stands out from the entire line of drugs in that it contains an increased concentration of the active substance. Therefore, it is more economical - less product is required to treat a larger area. The drug is a universal substance that has the same effect on annual and perennial crops. Applicable over a wide temperature range. Can be used in the countryside.
An effective and inexpensive drug. Due to the fact that it penetrates the vascular system of plants, it kills them completely, both ground organs and the root system. The drug is popular because it is effective against weeds belonging to the hydrophytic group (sedge, etc.). After using it, you can plant cultivated plants within a week. The drug does not settle in, does not affect and is suitable for affecting any herbs. It is allowed to be used on dacha farms.
- continuous action herbicide containing increased concentration chemical substance imazapyr. Affects almost everything. It is highly effective - a week after its use, all herbs completely die. It is used both for industrial purposes and for personal use.
. Suitable for the destruction of all types. In sunny weather, the effect of use occurs after 3 days. On average, it will take a week to achieve complete weed control. Cultivated plants can be planted in cultivated soil after 3 weeks.
Suitable for getting rid of all types of weeds. It does not have soil activity, which means it can be used before planting any crops. Affects all plant organs. If you use it correctly, following all the manufacturer’s recommendations, you can avoid harm to humans and animals.
"Octopus". Contains an increased amount of the active ingredient - glyphosate (

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

Herbicides are classified according to the following criteria:

by chemical composition— Herbicides are divided into organic and inorganic. However, currently mainly organic herbicides are used in agriculture.
according to the principle of action on plants (i.e. phytotoxicity) differentiate herbicides continuous(general exterminator) and electoral(selective) actions. When treating soil or vegetative plants with continuous action herbicides, destruction of all vegetation is observed. Preparations of this group are not recommended for use in crops. They are used mainly for the destruction of unwanted vegetation along canals, field roadsides and non-agricultural lands (right-of-way for railways and highways, etc.)
by the nature of the effect on plants Herbicides are also divided into contact and systemic. Contact herbicides (DNOC, sodium pentachlorophenolate, Reglon, 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, TCA-trichloroacetate, banvel, suffix) can penetrate and move in plant organs. Moreover, most of these drugs have by selective action, those. destroy some plant species and do not damage others.
in relation to botanical classes of plants organic herbicides systemic action divided into groups: Antidicots. These include 2,4-D, 2M-4X. These compounds are used to destroy broadleaf (dicot) weeds in monocot (cereal) crops. Anticereals. Herbicides of this group suppress monocots, and at optimal rates do not damage dicotyledonous plants. These include sodium trichloroacetate, dichloroalurea, dalapon, etc. Herbicides of this group are used to destroy cereal weeds mainly in crops of broad-leaved crops - sugar beets, sunflowers, etc.
by application methods herbicides are divided into two groups: Soil preparations (diuron, prometrin, propazine, simazine, tillam, eptam, etc.). They are introduced into the soil without subsequent incorporation or with incorporation with 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 in dry form (granulated) or by spraying the soil. Preparations used to destroy vegetative weeds (2,4-D, 2,4-DM, 2M-4X, 2M-4XM, betanal, carbin, reglon, etc.) They are used only by spraying plants.
according to the terms of payment The following four groups of herbicides are distinguished. Preparations used before sowing cultivated plants (in autumn or spring). Preparations used simultaneously with sowing of cultivated plants. (local-band (row) application). Preparations used immediately or shortly after sowing cultivated plants, but before their emergence (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 timing of herbicide application is distinguished:

Post-harvest period– when preparing a site for next year in the fight against particularly malicious perennial weeds, which are more difficult to destroy in the spring of next year. It is important that the drugs 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 used mainly to control weeds emerging from seeds.

During sowing - pre-sowing– simultaneously with the sowing of spring row crops. Mainly soil herbicides are used with a small incorporation into the soil, usually using the belt method (in one unit with a seeder).

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

Pre-emergence– 2-4 days before the emergence of spring crops, followed by 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 mechanical tillage with chemical ones and on uncultivated lands in the presence of particularly malicious weeds.

Plant sensitivity to herbicides

Crop and weed plants have different sensitivity to herbicides due to their selective action. For each crop, only a herbicide is recommended to which the plants are resistant, and the weeds that infest 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-morphological. Thus, triazine derivatives (atrazine, prometrin, etc.) are characterized by biochemical selectivity. They suppress the processes of photosynthesis and transpiration in sensitive plants, as well as other biochemical processes leading to plant death.

The drugs have anatomical and morphological selectivity. These 2,4-D and 2M-4H herbicides, falling on the wide leaves of dicotyledonous plants, are well retained on them and penetrate into the above-ground 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 waxy layer of 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, to apply chemicals, use the period when cultivated plants have the greatest resistance, and weeds have the least resistance.

As weeds grow, the sensitivity of most of them to herbicides weakens. Young plants, which have delicate integuments and are characterized by rapid development and intensive metabolism, are damaged by herbicides in to a greater extent than the old ones. However, some perennial root-sucking weeds are more sensitive, for example, to the herbicide 2,4-D in the rosette phase than in the stem-beginning phase 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, during later phases of growth and development in weeds, the outflow of plastic substances from leaves to other organs increases and with increased foliage, more of the drug enters a unit of their surface area 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 low relative humidity 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 - somewhat later. New drug Satis is successfully used at +5 o C.

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

The form of the drug has a great influence on the effectiveness of the herbicide. If even a small amount of precipitation falls shortly after spraying the crops with 2,4-D herbicide, drops of it are washed off from the leaves and the drug does not have time to act on the plants. In such conditions, they have an advantage 2,4-D esters, which are faster ( in 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.

The development of large farms determined the need to find an easier solution for getting rid of weeds. Chemists studying properties various substances, came across the ability of copper sulfate (while studying the properties Bordeaux mixture) suppress dicotyledonous weeds. Later, the same property was discovered in the action of iron sulfate, copper nitrate, sodium chloride, sodium arsenite, sulfuric acid and other compounds.

The successful development of a new direction in chemical production has begun - the production of substances capable of destroying green plants. They were called herbicides (1944), from herb - plants, cide - to destroy. Herbicides were identified as a separate group of chemicals.

Types of herbicides

The development of the herbicide industry initially was limited to a continuous action on green plants. Later, by changing the concentration, we achieved the possibility of selective action of the herbicide on uncultivated plants. Their tiny doses, when diluted at high levels, contributed to the acceleration of plant growth, that is, they no longer inhibited the plants, but acted as a stimulant. Having identified a number of other necessary properties for the selective destruction of weeds, herbicides were divided into 2 groups:

continuous action,
selective (selective) action.

Today, the first group of herbicides is used in the construction of roads, stadiums, airfields, high-voltage lines, etc. Selective herbicides have found their niche in crop cultivation.

Ways to influence herbicides on weeds

Continuous herbicides destroy all vegetation, even cultivated plants. They are practically not used in agriculture today.

Selective action herbicides are divided according to their spectrum of action into:

widely selective. Destroy mono- and dicotyledonous weeds;
narrowly selective. They affect a certain class of weeds, down to individual species. Can be used in sowing cultivated plants.

According to the method of influencing weeds, herbicides are also divided into:

contact,
systemic.

The contact herbicide group requires contact with the plant. When spraying, the area of contact of the pesticide with the surface of the weed is large, which has a depressing effect on the entire plant.

Systemic herbicides, when in contact with a plant, penetrate inside and spread with a flow of liquid throughout all its organs. This property is especially significant for the destruction of perennial weeds with a powerful root system.

In agricultural production, broadly selective systemic herbicides are most often used, especially for multispecies weeds.

Herbicides are produced in the form of:

emulsion concentrates,
wettable powders of various color shades,
suspensions.

How to use herbicides

To choose the right herbicide, you need to do some research before purchasing it. preparatory work:

roughly estimate the degree of weediness in the field;
determine the species composition of weeds.

Taking into account field weediness is a very important indicator. If the dose of herbicide is insufficient (the desire is not to poison the soil too much), not all weeds will disappear. Some will survive under these conditions, and it will be necessary to apply the pesticide again. If you apply too much, the crops will suffer.

Special reference books provide standards and combinations of herbicides according to: the species diversity of weeds, the degree of weediness of the plantings, the type of soil and its properties.

Methods and terms of depositing

The timing and methods of treatment with pesticides depend on the type of herbicide. If a continuous non-selective action herbicide is used, it is necessary to protect the cultivated plants before applying it. When using a targeted herbicide, the age of the weed must be taken into account. With age, some weeds increase the degree of resistance to the herbicide, intensively weed the crop, thereby reducing its yield (sometimes by 30-40%).

According to the timing of application, they are divided into pre-emergence and post-emergence.

Pre-emergence application is carried out before sowing seeds, during sowing and for some time after sowing.

Post-emergence preparations are applied from the phase of weed emergence, tillering and reaching a height of 5-10 cm. Most weeds die when applied in the seedling phase; with age, their resistance to the herbicide increases.

Pre-emergence applications typically use soil-based herbicides. They are usually applied to moist soil, which makes it easier for the drug to distribute in the applied layer. Special root herbicides are applied in the form of granules and embedded in the target soil layer. Foliar herbicides are applied to green plants, spraying vegetative organs (leaves, stems).

Duration of action of the herbicide and its harmfulness

To increase the effectiveness of the herbicide, it is necessary to create certain environmental conditions. So, soil and root herbicides are applied to moist soil. When dry, they are inactive and only accumulate, and then, with watering or precipitation, their increased quantities destroy all types of vegetation (weeds and cultivated species).

After treating the above-ground parts of the weeds with herbicides, dry sunny weather is required for 2-4-6 hours. Washing off the drug from plants requires re-treatment. The drug that gets into the soil does not affect weeds, but accumulates in the soil.

Undegraded herbicides large quantities water is washed out of the soil and enters various bodies of water (ponds, lakes, rivers, seas), where it enters plants, river and sea animals, and, ultimately, the human body.

Of course, time plays a role. Some herbicides are destroyed over time under the influence of biological decay, physicochemical absorption, and enzymatic destruction. But all of them, incl. and part of the herbicides that have broken down into chemical components have their effect negative impact on soil biota involved in the formation of humus. As a result, humus formation decreases, and hence soil fertility. Some systemic toxins enter the crop and dining table. In general, the effect of the drug and its toxins lasts for a very long time.

The duration of action of herbicides is clearly demonstrated by the drug Agent Orange, which was used by the United States in Vietnam. The drug, a mixture of defoliants and herbicides, was intended to destroy forest vegetation, but at the same time it was dangerous for people. Upon returning home, American soldiers were sick for a long time and died from oncological diseases gastrointestinal tract, respiratory organs, lesions nervous system. After the war and to this day, children are born in Vietnam with various disabilities. Therefore, even if your home plot is heavily infested with weeds, think before using pesticides.

The use of herbicides in summer cottages

If it is impossible to do without the use of pesticides, check out the catalog of drugs approved for use in agriculture. Select herbicides that have a short decomposition period and do not accumulate in the soil.

Today, Lintur, Hurricane, Tornado, Agrokiller, and Physilad are offered in small packaging for treating plants and soil. The most effective technique is to prepare the solution according to the accompanying recommendations and spray the green weeds. The duration of exposure is from 8 to 12 days. Within a month, the above preparations decompose and do not accumulate in the soil. The effect and duration of preservation of the components of the decomposed drug are in the specialized literature.

Health protection when using herbicides

Herbicides are poisons with a high degree of harm to health. Therefore, when using herbicides in your work, it is necessary to take personal protection measures.

Work only in calm weather.
Work in clothing that completely covers exposed areas of the body (head covering that covers the neck, glasses, respirator, long-sleeved robe, gloves, trousers, boots).
After work, change your clothes completely, take a shower, drink milk.

Drinking alcohol can be fatal.

Worldwide production and use of herbicides amounts to 4.5 million tons of drugs annually.
Natural living herbicide. In the Amazon, ants (s/s formicines) live in symbiosis with trees of the genus Duroya. By injecting formic acid into any type of growth, except Duroya, they clear the forest of weeds and other trees.
Using No-Till technology, it is possible to control weeds without herbicides if, without allowing flowering, the weeds are destroyed, leaving their remains between the plants. Leave all crop residues on the field. Due to the layer of mulch, weeds cannot emerge and germinate freely. After a few years the field is cleared.
Use of green manure. Green manure crops sown before going into winter, releasing allopathic substances, act as herbicides.
In large fields the soil is kept in the form of green vapor. Under green fallow, dense sowing of perennial forage crops is used. Over two years, under green fallow, the number of weeds is reduced by 3 times.