Biological agents that are used for control of insects, weeds and pathogens produced from living organisms are called biopesticides. Micro-organisms such as viruses, bacteria, fungi, protozoa and mites may be used as biopesticides.
1. The manufacture of methyl isocynate (MIC) was started in 1980 in India to make Serin (carbaryl), a powerful pesticide that can kill more than 100 types of insects attacking 100 different crops.
2. Many of the chemical pesticides, which are used to control several crop pests also affects the beneficial organisms.
3. They also bring about considerable damages to living organisms because of their hazardous effects in the environment. There was an enmasse killing of more than 4,000 people, many animals and plants, when methyl isocyanate (MIC) gas leaked out in the night of 2nd and 3rd December, 1984 from the underground reservoir of Union Carbide Factory at Bhopal. This is mentioned as Bhopal Tragedy. Many of the people exposed to this poisonous gas are suffering even today.
4. Majority of microorganisms such as viruses, bacteria, fungi, protozoa and mycoplasma are known to kill insect pests. The suitable preparations of such microorganisms for control of insects are called as 'microbial insecticides'. These are non-hazardous, non-phytotoxic and are selective in their action. They are eco-friendly not responsible for environmental degradation. The most frequently used bio-control agent is Bacillus thuringiensis and Pyrethrum extracted from the inflorescence of Chrysanthemum belonging to Asteraceae.
B. thuringiensis is a widely distributed bacterium. It is a saprophytic bacterium and can be isolated from soils, litters and dead insects. It is a spore-forming bacterium and produces several toxins such as exotoxins and endotoxins in crystallized forms. The bacterium is harmful to lepidoptera insects. After infection of spore, larvae are damaged due to the secretion of a single large crystal in the cell. This crystal (toxin) is proteinaceous in nature.
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