How would you control the insects and microorganisms in food grains?

Pesticides are used for controlling pest. They are either applied by spraying or by fumigation. Malathion and pyrethrum are common pesticides. Fumigation is a better method. Fumigants consist of volatile chemicals, which quickly vapourise and kill the insects without affecting the grain. Ethylene dibromide and aluminium phosphide as well as copper oxychloride are the two common fumigants.