When did the Church in the West begin communicating in Latin, instead of Greek?

Since the Gospels, Paul's epistles, and the other books of the New Testament were written mostly in Greek, as well as much writing of early Church fathers, it stands to reason that much – if not most – of the early Christian scholarly writings were in the Greek language. In addition, the languages that were spoken by those Christians are Syriac and Greek. By the early middle ages, however, it is clear that nearly all scholarly writing in the West was done in Latin. When did Christian scholars in the West begin writing and publishing works primarily in the Latin language, instead of the Greek language? Why?