Drought, frost and hail have combined to ravage Europe's wine grape harvest, which in key regions this year will be the smallest in half a century, vintners say.

Thierry Coste, an expert with the European Union farmers' union, said Wednesday that France's grape harvest is expected to slump by almost 20 percent compared with last year. Italy's grape crop showed a 7 percent drop — on top of a decline in 2011.

"Two big producing nations, France and Italy, have not known a harvest so weak in 40 to 50 years," Coste said. "All the major producing nations have been hurt."

In places where vintners were already facing a small margin of profit, many could be facing survival problems, said Coste of the Copa-Cogeca union.

"In certain regions, there will be many vintners in big difficulties because of the collapse of the harvest," he said.

The European wine harvest automatically has a global impact since it accounts for some 62 percent of the worldwide wine production.

For more, see: Europe's wine grape harvest to be smallest in half a century, vintners say