Explain in brief about the alternate methods to be followed to prevent the harmful effects of over usage of pesticides.
(OR)
Mention any four effective methods of controlling pests, which are less harmful on environment based on biological principles.

Explanation

Some of alternative pest control methods are
(1) Rotation of Crop: Growing different crops on a particular piece of land in successive years.
(2) Studying the life histories of the pests: When this is done it is sometimes possible to sow the crops at a time when least damage will be caused.
(3) Biological control: Introducing natural preator or parasite of the pest.
(4) Sterility: Rendering the males of a pest species sterile.