Chemical substances which are capable of killing almost all forms of living organisms in the fields of agriculture, forestry and household are biocides. These can be insecticides, fungicides, herbicides, nematicides, miticides, molluscicides, and rodenticides.

Insecticides are used against insects, their eggs and larvae found in agriculture, industry and household. Even though the insecticides have contributed towards agricultural revolution in the 20th century, these have altered our ecosystem and poisonous insecticide residues persist in food and drinking water. A balance between agricultural use and environmental health issues is very difficult to maintain. We must try it always with new ideas and more research.

There are various kinds of insecticides and they include:

• Organochlorines: DDT, aldrin, chlordane, endosulfan. endrin, dieldrin, heptachlor, lindane, pentachlorophenol and hexachlorobenzene. Mustard gas is used in the war as chemical weapon.

• Organophosphates: azinphos-methyl, chlorethoxyfos, dichlorvos, fenthion, malathion, mevinphos, parathion, parathionmethyl and tribuvos.

• Carbamates: used as insecticides, fungicides and herbicides in agriculture. Used against mosquitoes inside the buildings. These are aldicarb, carbofuran, carbaryl, methomyl and methyl carbamates.

• Pyrethroids: These are natural insecticides developed from the plant product (dried flowers) called pyrethrum. Permethrin, remethrin, cypermethrin, bifenthrin, tetramethrin, transfluthrin and many more belongs to this group and these are produced by adding chlorine, bromine, nitro group or others.

• Neonicotinoids: these are the synthetic analogue of natural nicotine. These are often used as substitutes for organophosphates and carbamates. These are clothianidin, nitenpyram, thiamethoxam, acetamiprid, clothianidin, nithiazine and thiacloprid.

The other plant products include caffeine, nicotine, and neem products. Insecticides are poisons and we must be very careful.