CBSE Class 9 Answered

i) Weed control - This is done through use of weedicides,  mechanical control and biological control.

ii) Insect pest control - Through use of insecticides.

iii) Control of crop plant diseases - by treating the seed or soil or by spraying fungicide solution on infested parts.

In addition, the crops in the field can be protected by using resistant varieties of crop plants, selecting optimum time of sowing crops, crop rotation, clean cultivation and summer ploughing.