Complex sentence: The grape is grown in diminishing quantities at the southern end of the island, following "phylloxera" devastated the Madeira's vineyards the grape became more common on the mainland, there known as Esgana or Esgana Cão.
Split into simpler sentences: The grape is grown in diminishing quantities at the southern end of the island. After "phylloxera" devastated the Madeira's vineyards the grape became more common on the mainland, where it is known as Esgana or Esgana Cão.