WESTPAC stands to lose up to $NZ22 million ($17.38 million) from the collapse of a New Zealand winegrower with other Australian banks believed to be significantly exposed to the struggling wine industry.New Zealand wine industry experts and insolvency practitioners believe dozens of wineries could also soon slip into receivership after the boom on the back of the country's sauvignon blanc variety begins to splutter. The sector is suffering from chronic oversupply and plummeting prices.