Pesticide may be a chemical compound, biological virus or bacterium or disinfectant used for preventing, mitigating or repelling pest infestation. Pests such as plant pathogens, insects, weeds, molluses, birds, fish, mammals, nematodes and microbes spread disease or cause loss to the property.

Here again, we are faced with advantages of using pesticides as well as disadvantages of causing pollution in almost equal proportion. Only 3-5% pesticides in the form of insecticides and herbicides are effectively administered. The rest (95%-97%) of insecticides boomerang upon us through land produce, water bodies and atmospheric fallouts. Some of the identified channels are as under:-

1. Manufacturing industries generate solid waste rich with pesticides rejects. Carelessly disposed pesticide waste gets leached with the falling water. Improperly treated effluent also reaches water bodies. Vapour/particulates emissions fall down on earth with rain water and get deposited in water bodies.
2. Pesticides treated agricultural fields run off excess pesticides into nearest water bodies.
3. Excess or expired pesticides discarded in inappropriate manner without adhering to pollution control norms, either flows with the stream or get leached into the land surface from where it find its way to water bodies.
4. Aerial spray drifting with air to unintentional targeted area and species.

5. Sprayed into water bodies to destroy algae.

    

Physical and chemical properties of a particular pesticide is also instrumental in polluting water such as its biodegradability, binding strength, solubility, vapour pressure, texture, water retention characteristic and organic matter content. Apart from its properties, excess pesticides spraying may also lead it to the water bodies. Smaller the route, better are the chances. Pesticides sprayed in excess may percolate or leach through the soil. It may flow with other effluents or storm water as runoff. Accidental or negligence spillage may also have the same fate. Pesticides impregnated in eroding soil may be carried away to the water body.

It has been found that pesticide run off has killed all the fish in a particular pond or stream. Herbicides administered into the water body to mitigate wild growth such as algae are also quite dangerous. Excess destruction of aquatic plants may deplete food resource of the fishes. The dead aquatic plants start rotting depleting oxygen content of water technically termed as "Biological Oxygen demand". If fish does not suffer fatality then there is greater chance that these pesticides may harm indirectly. The fish may abandon their nesting and brooding zone hence reducing population. It may decrease immunity to fight disease. The fish may lose its reflexes and become a predator's delight. The amphibians are also suffering due to effect of pesticides on water bodies. Ponds are the nearest of all the water bodies and is dependent upon "water seeks its own level "mechanism.

Therefore, pesticides enriched water from household kitchen garden, farms and agricultural fields and even from washings from grain storage reach nearby ponds.

The most comfortable resort of tadpoles is the pond and murky land. It has been found that due to pesticides enriched water in the ponds, tadpoles take more time to transit into frogs and the frogs are losing their size lately.