Cognac is the most famous brandy in the world and its made from a grape most people have not heard of, the ugni blanc. Disease in the vineyards, including mildew, are cutting this year's harvest of the ugni blanc significantly.
Cognac can come from only one small region of France. With demand for Cognac growing, a bad year hurts brands like Martell and Hennessy because they are unable to count on a reliable supply of grapes.
The Bureau National Interprofessionel du Cognac says production could be off by 25-30 percent. That will likely cause prices to climb in future years.