Could anyone correct these sentences?

Please correct the sentences below.
Thanks a lot.

1.The pod protects the grain against invasion from insects.

2.Flavor is the main ingredient of  in cooking.

3.Civilizations were created in areas that were good place for cultivation. (i.e. the areas were fertile)

4.When they found discovered that coca could be used to is a treatment of diarrhea, the demand of is was for it increased.

5.Hard working at on the farm forced  stimulated the slave to escape.