Why should preventive measures and biological control methods be preferred for protecting crops?

Why should preventive measures and biological control methods to preferred for protecting crops?

Why should preventive measures and biological control methods should be preferred for protecting crops.

Preventive measures for birth control is -

Why should biological control of pests and pathogens be preferred to the conventional use of chemical pesticides?

Why should biological control of pests and pathogens be preferred to the conventional use of chemical pesticides?

Describe the methods of biological control of mosquitoes.