Explain the various preventive measures against insect pests.

Preventive measures against insect pests:

(i) Root cutting type of insects is controlled by mixing insecticides in the soil.
Example — chloropyriphos.

(ii) Stem and leaf cutting type of insects can be controlled by dusting or spraying the contact insecticides.
Example — malathion, lindane and thiodan.

(iii) All sap sucking insects can be controlled by spraying systematic insecticides.
Example — dimethoate and metasystox.