Pesticides include herbicides, fungicides and insecticide. They are used especially in a monoculture to control agricultural pests.
Most pesticides kill the harmful organisms, as well as, the harmless and beneficial ones. For example, insecticide kill pollinating agents like need and butterflies along with pests like leafhoppers, stem borers and y beetles. In addition, animals like toads and bird that used to feed on the killed organisms find that their food source is gone and move to other areas, thus affecting the ecosystems. These are the immediate results of spraying pesticides.
When crops are sprayed with pesticides, some fall on the crops and some fall on the ground. When such crops are eaten, the pesticides tend to accumulate in the body of the consumers. Over a period of time, the pesticides accumulate in their bodies, building up to toxic levels and causing them harm.
The pesticides that fall on the ground get into the ground water and eventually reach surrounding water bodies. Here, they get into the bodies of living organisms and cause harm.
Today, farmers are encouraged to use pesticides with great care and only when essential. In many countries, the law forbids the use of harmful pesticides like DDT. Scientists have produced a number of pesticides which do not build up in the bodies of living organisms. Many farmers also control populations of insect pests by introducing animals which prey on them. However, care must be used to make sure that the introduced predator does not upset the ecosystem.
