(Bloomberg) - France cut its outlook for wine production for a fourth time after botrytis rot due to wet weather caused grape losses in Bordeaux and Burgundy, adding to damage from poor flowering and summer hailstorms.

The volume of the 2013 vintage may rise 2.2 percent to 42.3 million hectoliters (1.12 billion gallons) from 41.4 million hectoliters in 2012, the Agriculture Ministry wrote in a report late yesterday. The forecast was cut by 1.74 million hectoliters from a month ago, equivalent to 231 million bottles.

The threat of rot by botrytis fungus prompted growers in Burgundy, Bordeaux and southwest France to harvest early, sometimes picking not fully ripened grapes, the ministry said. Rot also forced “major sorting” and cut volumes in Alsace, the Loire Valley and Charentes, according to the ministry.

“Botrytis developed in an exceptional manner in October in the western regions, the southwest, Burgundy, Beaujolais and Alsace, favored by frequent rainfall,” the ministry wrote.

The rot at grape-picking time comes on top of a cold and wet spring that hampered flowering, and hail damage in Burgundy in July and Bordeaux in August.

France’s production of designated-origin wines is forecast to drop 3.1 percent to 19.1 million hectoliters, from last month’s outlook for volume to be little changed. The volume of wine for distilling is seen slipping 1.8 percent to 7.45 million hectoliters.