Pesticides are a class of synthetic chemicals used to control the pests of crops. Pests can be an insect, disease or weed or sometimes non - insect pest like rats.

Various chemicals used to control the pests can cause large scale pollution - as less than 5% of applied pesticide reaches the actual pests and balance 95% enters the eco-system. The pesticides may remain in plant bodies and may accumulate in edible part of crops or pesticides may persist in soils to cause serious damage to biological balance in the soil. Pesticides can also enter ground water and may act as source of water pollution.

Some important pesticides commonly used in agriculture are:

Organo-chlorine chemicals

They are highly dangerous pesticides having the ability to persist in plant bodies and soil for long period to cause innumerable ecological and health hazards later.

Examples: DDT, BHC, endosulfan, heptachlor and chlordane.

Organo - phosphorous chemicals

They are also dangerous pesticides with ability to kill many useful bacteria besides killing the pests. They act as a source of pollution of agricultural land and ground water.

Examples: Phorate, methyl parathion.


They are used as insecticides, acaricides or nematicides to kill insects, mites and nematodes respectively. They can kill many aerobic and anaerobic bacteria in soil. They are easily escaped in underground water- when excess dosage is used.

Examples: Carbofuran, aldicarb and carboryl.

Ethylene Di Bromide (EDB)

They are volatile liquids used to produce gaseous poisons to kill stored grain pests. They can leave traces of dangerous chemicals on grains and cause food pollution.


Many triazines like Atrazine, Simazine are commonly weedicides to kill weeds in agriculture. They have potentiality to remain in soil and to be flown into ground water to cause drinking water pollution.

Phenoxy alkonates

They are the weedicides causing serious damages to the ecosystem, as they can kill variety of plants apart from weeds. They can also remain in soil and can cause water pollution - when they fail to degrade in soil medium.

Examples: 2,4 - D, 2,4,5 - T

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