Pesticides are chemicals that are sprayed on plants to prevent plant diseases. There are broadly five categories of pesticides:Fungicide - which acts against the fungi that harm the plants or crops.Herbicides - which are used against the weeds present with the crops that harm the crops.Insecticides - which act against harmful insects.Acaricides - which help in protecting the plants from mites.Nematicides - which are used to control the nematodes that attack the plants.