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Oidium and the Vineyard

by Staff Writer - A. Heinzman | June 17, 2011

One can definitely say that agriculture presents many stressful challenges. A seemingly infinite amount of variables exist that can affect a crop. Soil types, rainfall, temperature, sunlight and wind are all variables that can determine the success or failure of a crop. In addition to these natural considerations, life based variables can wreck havoc on agriculture endeavors. Pests in the form of insects, bacterial infections, fungi and rodents can all have equally negative affects on crop quality and output. Like all other agricultural endeavors, the vineyard is not excluded from this problem.

Beginning around the early 1830s American vintners began to notice a strange disease affecting their vineyards. Cultivated vines located within the eastern parts of the United States began displaying strange mildew growths on their leaves. These growths initially attacked only shaded areas of the vine. Shortly after the initial outbreak, the mildew growths would soon move to encompass the entire vine. This resulted in the vines withering and the grapes being ruined. The vine itself however would survive the attack.

Moving forward to about 1845, an English gardener known as Edward Tucker noticed mysterious mildew conditions on the grape leaves of his vineyard in Margate, England. The powdery mildew affliction quickly spread to various outdoor trellises of grapes. The conditions were the same as those observed by the American vintners; the powdery mildew would eventually consume the entire plant and the grape crop would be ruined due to split and decaying grapes. Edward Tucker's problem raised a few eyebrows and it was soon determined that the mildew was a fungus not indigenous to Europe. While the fungus had been identified, a practical solution for controlling the fungus as well as the origin of the fungus had not yet been determined.

By the early 1850s an epidemic was visible within the vineyards of Europe. Shortly after the powdery mildew destroyed Edward Tucker's grape harvests, the same powdery mildew began to turn up in King Louis-Philippe's royal gardens. After this appearance, the damaging powdery mildew appeared in Baron de Rothschild's grape house just outside of Paris. By the end of the 1840s, Oidium--as the mildew came to be called--could be found in every vineyard throughout France. This simple fungus threatened to destroy Europe's vineyards of Vitis vinifera.

The results of the Oidium disease were clearly visible. During this time, French wine production fell from 11 million hectoliters to 3 million hectoliters. The characteristics of the disease were also clearly visible. The origin of the disease as well as a cure seemed to baffle many individuals. As it is with much of the unknown, logical arguments as well as ignorance abounded. Italian peasants whose livelihood depended on the vine placed the blame on the fledgling railroad and telegraph industries. In other areas the religious community warned that the wrath of god over the sins of mankind was the source of the disease.

By the summer of 1854 the grape industry of southern Europe was in serious trouble. In what one author referred to as a biological catastrophe, the Oidium fungus had a chokehold on wine production that threatened the future of the winemaking profession. A solution to the problem was desperately needed. To attest to the seriousness of the problem, a French society offered a prize of twenty thousand francs for the development of a cure. Many different solutions were presented, many of which were ludicrous remedies that were ineffective. Of interesting note is that some individuals looked to nature for a cure and noticed something rather peculiar. The Native American vine of Isabella seemed to be naturally immune to the Oidium problem. What many individuals at the time did not realize was the fact that the Isabella variety had evolved to sport a natural immunity to the Oidium and that the importing of Isabella cuttings was the vector of the disease.

By the time the Oidium had been recognized as an epidemic, it had been generally known that Oidium was fungal in its nature. Knowledge also existed that a potential remedy existed with the use of sulfur dusting on the diseased plant. While crop dusting in theory seemed to be a plausible solution, in practice the application was mind-boggling. The sheer amount of infected vineyards required copious amounts of chemicals along with detailed logistics and application techniques never before attempted at such a grand scale. Nevertheless, the sulfur dusting solution was adopted and began in earnest at around 1852. For five years a continual application of sulfur based chemicals was applied to the vineyards of France. The initial result of this colossal endeavor was a sulfur pollution of the countryside. The good news was that by 1858 the Oidium epidemic had been defeated. The European wine industry of the mid 1850s would prosper into a new golden age of winemaking. Future issues were however on the horizon including the Phylloxera louse observed in the late 1800s.

Today Oidium is recognized as a common pathogen of the Vitis species. In modern times the pathogen is referred to not as Oidium but rather Uncinula necator. This powdery mildew disease still affects vineyards around the world but modern vineyard management techniques as well as modern fungicides have assisted with the control of Uncinula necator. Looking to the future of plant genetics and species development, it is plausible that natural immunizations could be introduced that would prevent Oidium from attacking certain variants of the Vitis variety. For the immediate future, the only methods available for the control of Uncinula necator are fungicide application.

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