This book deals with the introductory concepts of pesticides and their classification. The role of herbicides in the controlling the weeds was explained in detailed. The importance of fungicides as chemicals and biological agents in combating the economic losses was described. Insecticides like organic insecticides and DDT were described in this book and their role in regulating insect species was emphasized. The nematicides can control the growth of nematodes in the crop plants and in this book, basic concepts of nematicides were described. Rodents in the crop species and their control via use of rodenticides was described in this book. The microbial pesticides and their role in the crop improvement were explained with examples. The biochemistry of the pesticides and their chemical interactions were described. The resistance of pests against pesticides was explained in detail.