Explain the methods to control pests which have less harmful effects.

Hint: A serious threat to humankind are the pests like rats, termites, fungus which have a harmful effect on the human body. The chemically-treated pests harm the plants too. There is a need for organic pests which will kill the harmful pests and have no effect on plants, animals, and humans.

Complete answer:
There are three ways to control pests.
The biological control is done by suppressing or controlling the growth of the pests. It is one of the most harmless, non-polluting, and self-perpetuating control methods. This can be done by using predators like bees, whose larvae majorly are fed by green flies. Many parasitoid insects also help in pest control as the wasp lays eggs on aphids and when the eggs are hatched the aphids die. Aphids are harmful to the plants.
Crop rotation is one of the most effective methods of organic farming and controlling pets. The main objective of crop rotation is to interfere with the needs of the pets through its life cycle.
Most of the pests show a distinct preference for a particular stage of crops. The trap crops attract insects or other organisms to protect the crops from the attack of the pets. The trap crops are either planted at certain parts of the field or adjacent to the main crop.

Note: Parasitic nematodes are used to kill or sterilize the pests. Biological control of pests does not destroy the pets completely. Most pets or insects start their cycle as adults. The adult phase comes during spring, so the crop rotation from one year to the other helps in moving the host plant. This prevents the growth of the pests on the host plant.