Oidium, Powdery Mildew
A disease that affects the vine brought about by a parasitical fungus that develops on the surface of the green parts of the plant. It dries up the leaves and grape bunches and leaves them covered with a white powder. This disease was unknown in Europe until the 19th century when American grafts were brought from overseas to try and remedy it, thus leading to the spread of philloxera. Oidium can be effectively cured by spraying the leaves with sulphur. The sulphur vapours also fight off the Botrytis fungus which is external.