The term Pesticides is defined by FAO in collaboration with UNEP (1990) as chemicals designed to combat the attacks of various pests and vectors on agricultural crops, domestic animals and human beings. The word “Pesticides” is an umbrella term for all insecticides, herbicides, fungicides, rodenticides, wood preservatives, garden chemicals and household disinfectants that may be used to kill some pests.
There are a large number of pests which are constantly eating away and destroying the crops whether indoor or outdoor being grown with hard work by human beings. From time immemorial we have been fighting the pests with homemade bio pesticides. The first synthesized pesticide is believed to be DDT (dichlorodiphenyltrichloroethane) in 1874 and used in the 2nd world war also. To alleviate and even kill these pests we are forever bringing out newer and newer chemical formulations, broadly named as Pesticides. This has become a regular scenario as the pests outgrow the effects of chemical formulations and then newer formulations are needed or the dose needs to be increased.
Of late there has been considerable research into these types of Pesticides and their use in cropping to produce food has increased. Green Revolution owes a lot to use of Pesticides. Pesticides are also used against vector borne diseases in human and animals. Use and development of Pesticides are a necessity for us to be self-sufficient in food and our well being and of good health.
Types of pesticides: 1. Chemical Pesticides, and 2. Organic Pesticides.
Chemical Pesticides: Systematic and Contact type
Contact type pesticides: The pesticides, in suitably diluted form with mainly water, are sprayed over the infected plants and effect on insects is they come in contact with the sprayed insecticide. The action is very fast and immediate.
Systematic Pesticides: This type of pesticide is ingested into the plant through leaves and roots and acts when insects eat the plant. The action by this type of pesticides would be later but be more effective and persist for more time.
Classification of Chemical Pesticides based on composition:
Organochlorine: this type of pesticide has five or more chlorine atoms. Organochlorines were the first synthetic organic pesticides. Some of the common pesticides are DDT, lindane, endosulfan, and aldrin. This type is stable type of compounds and persistence is good. Used in cultivation of grapes, lettuce etc. and also for eradication of malaria, dengue. The action is through ingestion and by contact.
Organophosphates: this type of pesticide is esters derived from phosphoric acid. This pesticide is very common in agriculture as insecticides and miticides and action is by ingestion and contact. Some examples are Parathion, Malathion, Diaznon and Glyphosate.
Carbamates: These types of pesticides are esters derived from acids or dimethyl N-Methyl carbamic acid and used as insecticides, herbicides, fungicides and nematicides. Their action is fast though less persistent than other types of pesticides. Some examples are Carbaryl, Carbofuran and Aminocarb.
Pyrethroids: these are extracted from chrysanthemum flowers known as pyrethrins. Now it is mainly manufactured synthetically. This type of pesticide acts on the central nervous system. Some examples are Permethrin, Cypermethrin and Deltamethrin.
Mode of formulation :
EC Emulsifiable concentrates fine suspensions of oil droplets in water; WP wettable powers are fine particles suspended in water; G granules are obtained by mixing the active ingredient with clay for outdoor applications; D dusts are to be applied dry mixed with clay etc.
WHO World Health Organization classifies pesticides as follows:
Class I a = extremely hazardous; Class I b = highly hazardous; Class = moderately hazardous; Class III = slightly hazardous and Class IV = unlikely to present any acute hazard in normal use.
We know and practice alternate crop practices in the field to reduce nematodes.
There are a large number organic pesticides used over the world mostly learnt from the elders of the community or from scriptures.
Organic or bio Pesticides are of many types e.g. Microbial e.g. bacteria, fungi, viruses, protozoa; Pheromones e.g. message bearing substances produced by plants and animals which interfere with mating or disrupt pest insect behavior; Invertebrate biological control agents e.g. parasitoids, predators and parasites; Botanical pesticides and Transgenic crops.
Neem Oil (Azadirachtin) is a very effective and largely used pesticide and is available in various concentrations for use.
Go Mutra (cow urine) of desi (common) cows is a highly effective pesticide to be used with certain formulation.
Tobacco is also used as a pesticide by farmers to fight pests in the crops.
Trichoderma, Verticillium lecanii, Metarhizium, etc. are mixed in the soil for giving protection against insects and their larvae. Trichoderma and its variants like T-22 are used for better plant growth and increased produce.