In Corsica, nurturing trees have been imported by the Genoese. They cover 30 000 hectares on the island. These hundred years old chestnut groves have seen many generations turn their fruits into flour, including the family of Williams Franchi. After the October harvest, fruits are dried over a wood fire for a month. Then they are shelled, dehydrated and sent to the mill. But since 2010, the Chesnut Gall Wasp attack the tree. The wasp Torymus sinensis, its only predator, has been introduced to defend the gold of the Corsican mountains: a biological war is engaged.