Pesticides are substances which are used to kill or block the reproductive process of unwanted organisms.
The three main categories of pesticides are:-
(i) Insecticides: These are used to control insects and curb diseases and protect crops.
(ii) Herbicides: These are used to kill weeds. Example- sodium chlorate (NaCIO3), sodium arsenite (Na3AsO3)
(iii) Fungicides: These are used to check the growth of fungi. Example-methylmercury