Oidium

Oidium, or ERYSIPHE, a genus of minute fungi infesting various plants, and especially important as the cause of a ravaging disease of the vine, popularly known as vine-mildew. The disease was first observed in Kent in the spring of 1845; it spread rapidly over the English vineries, and was observed about the same time in the vineries of Paris, and soon afterwards in those of nearly all parts of France, Italy, Greece, Tyrol, and Hungary, and in a less degree in the Rhine valley. Its ravages extended to Algeria, Syria, Asia Minor, and especially to the island of Madeira, where it nearly put an end to the production of the celebrated wine. The disease appears first in the leaves, these drop off, the plant loses strength through impaired nutrition, the young shoots fall victims, and lastly the grapes. Powdered sulphur was found useful as a cure, but the applications had to be very frequent; in consequence of its importance the duty of sulphur was reduced by the French government. It is probable that in this case, as in all diseases of the sort, the general vitality of the organism must be lowered before it will fall a victim. Over-cultivation and long use of the same ground are predisposing causes.