Downy mildew is one of the world’s most catastrophic and baffling diseases of grapevine. The disease occurs worldwide wherever the weather during the growing season is humid and rainy and temperatures are cool to moderate. Downy mildew affects all parts of grapevine and kills leaf tissue and causes defoliation. Prior to 1870, this disease was considered endemic to the USA. Since 1875, epidemics have also been reported in France, where it caused heavy loss to wine industry. When weather is favorable and no protection against the disease is provided, downy mildew can easily destroy 50-75% of the crop in one season. It was in search of chemical control of this disease that Prof. Millardet of the Bordeaux University made the accidental discovery of Bordeaux mixture in 1885.

APS publication number:  IW000083

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