Jan 072013

These days, agriculture has become very advanced. Due to the use of different techniques and tools, farmers are being able to produce more amounts of crops day by day. By using pesticides, the farmers are being able to kill all such pests and insects which can destroy their crops. Pesticides can simply be defined as the poisonous chemical compounds which are used to kill or control the pests which can damage and destroy the crops badly. They can be classified into many types on the basis of many factors. All such types and categories are mentioned below:

1. On the basis of pests: On the basis of pests, the pesticides can be classified into different types such as:

  • Insecticides: Insecticides are such pesticides which help to kill and control the insects.
  • Miticides: Miticides are such types of pesticides which help to kill and control the mites.
  • Rodenticides: Rodenticides are the pesticides which help to kill and control the rodents such as mice etc.
  • Herbicides: These are the pesticides which help to control different types of weeds and plants which act as obstacle in nutrition of the crops.
  • Fungicides: Fungicides are such kinds pesticides which help to control the growth of fungi.
  • Nematicides:  Nematicides are such types of chemical pesticide used to kill plant-parasitic nematodes.
  • Bactericides: Bactericides are the pesticides which can help in the destruction of different harmful bacteria.

2. On the basis of chemical composition: On the basis of chemical composition of pesticides, they can be categorized into:

  • Organochlorides: These are the organic compounds which are chlorinated with several atoms. They are very effective and very toxic pesticides. Their examples are Dichloro Diphenyl Trichloroethane (D.D.T.), Dieldrine, Chlorodane etc.
  • Organophosphates: Organophosphates are the esters of phosphoric and triphosphoric acids. They are very toxic too. The examples of such pesticides are Malathion, Parathion, Phosphomidon etc.
  • Carbamates: Carbamates are the organic compounds of esters of carbonic acids. They are very much effective against many insects and have less toxicity. The examples of carbamates are Aldecarb, Aminocarb, Baygon, Pyrethrines etc.
  • Triazines: Triazines are the groups of herbicides which are derived from urea. The examples of triazines are Simazine, Triazole etc.
  • Natural Pesticides: Natural pesticides are such types of pesticides which are derived from the plants, herbs and some other microorganisms. The examples of natural pesticides are Nicotine etc.

3. On the basis of mode of action: The pesticides can be classified into different types on the basis of mode of action. They are:

  • Contact Poisons: Contact poisons are used against insects in direct contact. For example, Nicotine, Malathion, Dichloro Diphenyl Trichloroethane (D.D.T.) etc.
  • Stomach Poisons: Stomach poisons are such pesticides used to kill insects having biting and chewing types of mouth parts.
  • Fumigants: Fumigants are such pesticides which produce fumes and vapours to show their effects on insects and other animals. They are used to treat soil or stored products of godowns and other stores.

Hazards or Disadvantages of Pesticides

When pesticides are used in low concentration, they show toxic effects against pests, weeds, fungi etc. Pesticides

and less phototoxic effects and even no effects against human beings. If the amount of pesticides exceeds the required minimum amount, then they enter in the bodies of living beings through food chain, which may cause great defect and even loss of living beings. Due to harmful role of pesticides, they show the following hazardous effects or disadvantages:

  • They are toxic in the nature when they are applied in the field. So, they not only kill the harmful insects, weeds, pests etc. but also the useful organisms which may be in contact. For example, honeybees, butterflies etc. may be killed due to pesticides.
  • It is presumed that the concentration of pesticides after entering the food chain of an ecosystem increases ten times when it passes from one trophic level to another trophic level.
  • Human beings also receive these pesticides through animal fats, milk, vegetables etc. and are subjected to cancer producing agent.
  • According to researches, certain pesticides have mutational defects on Deoxyribose Nucleic Acid (D.N.A.) molecules of human beings.
  • Due to loss of living beings in different trophic levels, the pesticides offset the ecological balance.
  • Uncontrolled or excessive use of pesticides affects the structure as well as the fertility of the soil.
  • Due to continuous use of pesticides, the pests can develop resistance or immunity against pesticides. Due to this, the farmers have to use higher doses of pesticides to protect their crops which degrades the environment.
  • Pesticides might be major cause of declination of reproductive capability in some organisms. Dichloro Diphenyl Trichloroethane (D.D.T.) interferes with the calcium metabolism, which gives rise to calcium deficiency and hence symptoms like thinning of egg shells of birds, weakening of birds etc. are seen.
  • They also harm livestock, wildlife, fishes and other aquatic animals. Useful nitrogen fixing bacteria in roots of leguminous plants may also be harmed.