With the need for pest control, man was faced at the dawn of his agricultural activity. With the development of crop production - an increase in the area of arable land, the emergence of monocultures, etc. - this problem began to acquire increasing importance. To get large crops, farmers had to use special means - pesticides. Classification of such compounds can be made according to various criteria. There are many varieties of such drugs.
Definition
Pesticides are any means intended for plant protection. Pestis in Latin means "infection", and caedo - "kill." Previously, such drugs in our country were simply called pesticides. Today in Russia it is the generally accepted name “pesticides” that is used in the world. Some types of such drugs can be used not only to protect plants, but also animals, and sometimes humans.
The systematic use of such products to protect agricultural crops from various kinds of insects, microorganisms, etc. began as early as the 19th century. In 1939, Dr. P. Muller discovered the special insecticidal properties of dichlorodiphenyl trichloromethylmethane (DDT). This was a real revolution in protecting plants from insects. Other chlorine-containing pesticides, as well as phosphorus-based products, were later developed. Synthetic pyrethroids, azoles, etc. became the third generation of such compounds. And of course, after the invention of a large number of varieties of such agents, among other things, a classification of pesticides by chemical composition and other characteristics was developed.
Varieties
They can be divided into groups currently used preparations intended for plant protection by the following characteristics:
There is also a hygienic classification of pesticides.
Differences in chemical composition
To protect plants, currently can be used drugs:
Classification of pesticides by chemical structure is convenient, among other things, in that it makes it easy to select the funds for one or another purpose that are most suitable in this particular situation. However, each such drug within the group still has its own characteristics and may differ from the “related” ones by the strength of the toxic effect on pests or even directivity.
Hygienic classification
The production of chemically pure preparations for plant protection is very expensive. Therefore, most pesticides contain various kinds of additives. When using such plant protection products, it should be borne in mind, among other things, that some of these impurities can be even more toxic than their active substance itself.
Such means should be selected taking into account possible harm to farm animals, fish in rivers and lakes located next to the treated fields, or humans. The toxicity classification of pesticides has been developed as follows:
potent poisonous - LD50 up to 50 mg / kg;
highly toxic - LD50 50-200 mg / kg;
medium toxic - LD50 200-1000 mg / kg;
low toxicity - LD50 more than 1000 mg / kg.
Also, all these drugs are divided according to the degree of resistance to:
Another hygienic feature by which pesticides are classified is the degree of their accumulation in living organisms. In this regard, there are means that can cause:
Thus, the most dangerous for farm animals will be a potent poisonous pesticide with supercumulation, very stable.
Intended classification
Crops can be damaged by different types of pests. Special drugs have also been developed against each of them. Accordingly, there is a classification of pesticides by application. There are currently more than 30 groups of such drugs for their intended purpose. But the most popular types of pesticides are still:
Aphids - designed to combat aphids;
acaricides - used from ticks;
bactericides - destroying bacteria;
herbicides - intended for weed control;
zoocides - used to kill harmful animals, such as rats or moles;
insecticides - used to control harmful insects;
fungicides - used to kill microorganisms, etc.
Classification of pesticides by mechanism of action
Penetrate harmful insects into the body, such drugs can be in different ways. In this regard, the drugs are distinguished:
According to the mechanism of action, contact and systemic pesticides are distinguished. The first variety of preparations covers parts of agricultural crops with a thin film. The death of insects occurs due to direct contact with them. Systemic pesticides penetrate plant tissues and subsequently move in their parts.
By the nature of the effect on the causative agents of the disease, such drugs are divided into protective (preventive) and therapeutic. There is also a separate classification according to the mechanism of action of herbicides. Such drugs can be selective or continuous. The first type of herbicide destroys only a specific type of weed. Continuous preparations kill all vegetation on the field.
Application methods
Classification of pesticides can, of course, be made according to the method of use. These drugs come in different forms on the market. Pests can be destroyed by:
Pesticides are also often included in lures. Some varieties of pesticides can be used in solutions. For example, planting material of crops is often processed in this way.
What harm can the environment cause?
The chemical composition, methods of application, purpose and mechanism of action are the main features by which pesticides can be classified. The use of pesticides is, of course, necessary. But still use such funds, of course, you need to be as careful as possible.
Almost all pesticides used today are toxic substances. And of course, they can be harmful to the environment. Such products pollute:
atmosphere;
hydrosphere;
soil;
biosphere.
Such drugs can be harmful to all living organisms. First of all, fish in water bodies suffer from them. According to statistics, from 30 to 70% of all pesticides used in the fields, unfortunately, fall into water bodies. Also, these substances cause great harm to birds and mammals. In them, they cause shifts in hematological parameters. In addition, these drugs act on birds as immunosuppressants. In some cases, pesticides are even capable of disrupting the individual or flocking behavior of birds and mammals.
Human impact
The classification of pesticides by toxicity was considered by us above. Even the most harmless substances of this group contain, albeit in a small amount, toxic substances. Of course, with the development of science, pesticides are becoming less harmful to humans. However, unfortunately, the modern means of this variety can not be called absolutely safe. In addition, pesticides introduced to the fields 20 and more years ago are still preserved in soil and water. Therefore, cases of pesticide poisoning today, unfortunately, are possible.
Pesticides can accumulate:
At the same time, they enter the human body, not only with food or water, but also simply from the air. Such substances can cause significant harm to people. First of all, they cause disturbances in the functioning of the nervous system. Also, such compounds are able to destroy the metabolic process and slow down cellular metabolism. Unfortunately, some of these drugs can negatively affect the production of hormones in the human body.
It is believed that the most harmful effects of pesticides are experienced by unborn children. Even in low concentrations, such substances freely penetrate the placenta.
Ecological farming
Pesticides, therefore, cause significant harm to humans. However, farmers can not abandon their use yet. Today there is no serious alternative to pesticides for the destruction of harmful insects and microorganisms. Without them, growing various kinds of crops can become extremely inefficient.
The only method that has high hopes in terms of reducing the harmful effects of pesticides on the human body is ecological farming. Using this technology, the plants themselves can be used to repel pests. For example, adherents of this technique often plant calendula next to onions. This plant repels the onion fly. At the same time, it is unpretentious and does not take too many nutrients from the earth.