Pesticides, Chemistry tutorial


Pesticides are the chemicals which we make use of to kill undesirable organisms. Whenever we state undesirable organisms, we are referring to organisms (plants, animals, insects and so on) that are injurious. Some of such organisms or pests eat our crops, whereas others spread diseases. Weeds for illustration can be considered a pest for just growing in the wrong position. Now, whenever we use some kind of chemical to control such pests, that chemical would be believed a pesticide. 


Pesticides are the products which destroy different agricultural pests, comprising weeds (that is, herbicides), insects (that is, insecticides), bacteria (that is, microbicides) and fungi (that is, fungicides). They cause economic damage to crop or ornamental plants and are dangerous to the health of domestic animals and humans. All the pesticides interfere by normal metabolic methods in the pest organism and often are categorized according to the kind of organism they are intended to control.  Significant pesticides comprise dichloro diphenyl trichloroethane (DDT), 2, 4-D ethion, malathion, formalin and bio pesticides. Pesticides are these days basic requirement for the agricultural production and almost each and every country in the world uses pesticides. An appreciable quantity of food is lost because of insect pests, plant pathogens, rodents, weeds, birds and in storage. Pesticide industry has developed considerably and has contributed extensively towards agricultural and public health.  

Classification of Pesticides:

The Pesticides can be categorized based on their origin and the pests they control.

I) Classification based on their origin:

Pesticides are categorized based on their origin into chemical pesticides and bio pesticides.

A) Chemical Pesticides:

These are further classified into four kinds:

  • Carbamates
  • Organophosphate pesticides
  • Organochlorine pesticides
  • Pyrethroid pesticides

B)  Bio pesticides:

These are derived naturally from the living organisms or their metabolites such as fungi, bacteria, plants and so on. They are categorized into three main groups: 

  • Microbial pesticides
  • Biochemical pesticides
  • Plant incorporated protectants

II) Classification based on the pests controlled:

Pesticides are categorized on the basis of the pests controlled into:

  • Insecticides: act on insects.
  • Herbicides: control weeds.
  • Algaecides: control the growth of algae.
  • Bactericides: act on bacteria.
  • Fungicides: act on fungi.
  • Larvicides: Inhibit the growth of larvae.
  • Rodenticides: control rodents.
  • Repellants: Repel pests via their taste or smell.
  • Avicides: kill birds.
  • Desiccants: Act on plants by drying their tissues.
  • Ovicides: Inhibit the growth of eggs of mites and insects.
  • Virucides: Act against viruses.
  • Nematicides: Kill nematodes which act as parasites of plants.

Production of Pesticides:

Pesticide production comprises at least three separate activities. The active ingredient is primarily synthesized in a chemical factory, then formulated in the similar place or sent to a formulator, who makes the liquid or powder form. The pesticide is then sent to the farmer or other certified applicator, which dilutes it prior to applying it to the fields.

Synthesizing the pesticide:

Whenever a new pesticide is first developed, it is prepared on a small scale in a laboratory. If the substance verifies viable, production starts in the factory. Batch or continuous manufacturing assures a high volume, possibly as much as 500 kilograms per cycle. Synthesizing a pesticide is a complicated chemical procedure which needs trained chemists and a large, sophisticated laboratory. The fundamental procedure entails modifying an organic molecule to form a pesticide. This might comprise any of a number of particular reagents and catalysts and often should occur in a controlled climate (example: in a certain range of temperature).

Once synthesized, the active ingredient is packaged and sent to the formulator. Liquid insecticides can be shipped in tank trucks or 200-liter drums. Transport of the active ingredient follows all the regulations for dangerous materials transportation. 

Formulating the pesticide:

A formulator acknowledges the active ingredient, measures out the proper amount, mixes it by carrier if it is to be a liquid pesticide or by inert powders or dry fertilizers if it is to be a dust pesticide, then bottles or packages it. Liquid pesticides are packaged in 200-liter drums when a large-scale farmer is the anticipated customer or 20-liter jugs for small-scale operations. Dry formulations can be packaged in 5 - 10 kg plastic or plastic-lined bags. The emulsified formulation is generally concentrated to render transport simpler (that is, the active ingredient generally makes up 50% of the emulsified concentrate), however granulated and dry pesticides are ready to use. The pesticide might be stored a short time prior to it is requested. Whenever it is ready for transport, the estimated essential amount is sent to the farmer, who dilutes the emulsified concentrate to make the amount of pesticide desired. In most illustrations, the final product comprises just 0.5 to 1 percent of the original active ingredient. The pesticide is now complete to be applied. 

Applying the pesticide:

There are some ways to apply a pesticide. The process by which Americans are most familiar is crop dusting; however its use is usually limited to large, flat areas. A plane loaded by 2000-liter (or larger) tanks flies over a field and sprays out the pesticide from booms. Booms are long, horizontal rods from which some of the sprinklers spray down. The other process is to attach the tanks and booms to a tractor and spray closer to the ground. For small farmers, the most economical technique of spraying is to use one or more workers by hand-held sprayers attached to small tanks. A hand pump can be taken the shoulder; its tank capacity is just around 3 to 12 liters. Small tanks having a capacity of around 200 liters are as well employed. The pesticides are applied having a hand gun. A rough approximation of the amount applied is 150 to 300 liters per hectare.

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