By Tom Pfeiffer and Angeliki Koutantou LONDON/ATHENS (Reuters) - The cash economy emerging after the closure of Greece's banks is beginning to paralyse the country's vital olive oil industry as farmers demand cash for supplies that distributors are unable to pay. With the country's lenders at risk of default, Greece's half a million olive growers, many of them small family businesses, fear the banks will raid their accounts and are refusing to accept large payments via bank transfer. "They want it in cash or they prefer to keep their olive oil in their tanks," said Chris Dimizas, managing director of extra virgin olive oil producer Greekpol in the northwestern Peloponnese.