Reduce the use of plastic bags

In English, if you want to refer to things in general, use the plural form of the nouns. Usually, examples are given in plural form. Recently, Penang people have been asked to use less plastic bags.

In one supermarket, the notice reads, 'Help to conserve nature, reduce the use of plastic bag.' In this case, since plastic bags are things in general, the notice should read, "Help to conserve nature, reduce the use of plastic bags"