(DailyHerald) - Wine production in France, the biggest exporter, may slump 16 percent this year to a four-year low after frost, thunderstorms and an August heat wave harmed vines and grapes, the Agriculture Ministry said. Output is forecast to slide to 42.9 million hectoliters (1.13 billion gallons) from 50.9 million hectoliters in 2011, the ministry wrote in a report on its website.