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Phylloxera in the Modern United States

by Staff Writer - A. Heinzman | June 28, 2011

By 1900 the Phylloxera louse had been successfully checked in its conquest of European vineyards. This was not a small undertaking but rather a major accomplishment. The accepted solution to the Phylloxera problem was eventually recognized as grafting a scion of Vitis vinifera onto a Native American hybrid Rootstock. The inherent nature of the failure of chemical pesticides to control the louse necessitated the rootstock approach. As a result, most vineyards in France required vines to be replanted. This resulted in the uprooting of remaining Vitis vinifera vines and replacing them with vinifera grafted on Phylloxera resistant rootstock. The rootstock approach was sound and research continued with the development of Phylloxera resistant rootstocks. It is interesting in that with all advances in research, a second Phylloxera epidemic would be seen at the end of the 20th century in California.

The history of Phylloxera in the United States is interesting to say the least. Phylloxera is a louse native to the Americas. Found in the northeast United States, Phylloxera and Native American wine species evolved to mutually co-exist in nature. By the time the Phylloxera problem was in full swing in France, the louse had crossed the Rocky Mountains and was affecting California vineyards as well. California vintners had found that accepting the French solution of Phylloxera resistant rootstocks was the answer and began replanting their vineyards. This replanting resulted in solving the Phylloxera problem in America. However the Phylloxera solution was short lived. By 1919 a new problem had arose and this time the problem was political rather than biological. The adoption of Prohibition in the United States destroyed the wine industry for a period of 14 years. By the 1930s, the future looked bright for vintners in California.

With Repeal in full effect in 1933, California vintners began the process of rebuilding their vineyards. With tremendous gusto, vintners turned to the scientific community when rebuilding their vineyards. About this time, the University of California at Davis established a separate College of Agriculture. Within the College of Agriculture a division of Viticulture and Enology quickly became a world leader in the areas of grape growing and winemaking. Vintners now had an excellent resource to assist with rebuilding California the wine industry.

The study and science of viticulture and enology really took off during the 1950s. During this time, graduates of the University of California's College of Agriculture began extensive research into every facet of winemaking in California. Recommendations concerning winemaking and vineyard procedures soon followed. During the course of this research, recommendations were developed concerning Phylloxera resistant rootstocks. The official line concerning rootstock selection recommended that the rootstock AxR1 be used in place of the default St. George rootstock. This recommendation came based on the research that AxR1 produced excellent yields, excellent quality and that AxR1 growth favored well in the soils and climate of northern California. Concerning resistance to Phylloxera, the fact that AxR1 rootstock shared its parentage with Vitis vinifera was taken into account. Even with the AxR1 rootstock being half-vinifera, AxR1's resistance to Phylloxera was still judged to be more than adequate. This recommendation would be the beginning of a new epidemic for Phylloxera in northern California.

Heeding the advice of the division of Viticulture and Enology at the University of California, vintners began expanding vineyards using the AxR1 rootstock. The initial results were outstanding with vines growing vigorously and producing high quality grapes. However, by the mid 1980s problems began to arise with Phylloxera. History is often filled with examples of blunders and the selection of AxR1 rootstock is a prime example. For on a visit to the Napa Valley in 1980, Dr. Pierre Galet of the department of Viticulture at Montpellier was surprised to find that AxR1 had been used as a rootstock. Dr. Galet pointed out that the AxR1 stock had long ago showed its susceptibility to Phylloxera in Europe. That the AxR1 susceptibility was overlooked demonstrates how important communication is within the field of research.

By 1983 a new Phylloxera crisis was observed. Vines planted on the supposed resistance of the AxR1 rootstock began to fail at St. Helena. The Phylloxera problem began to spread to other vineyards and the laboratories of the University of California began to assess the problem. It was discovered that a rare form of the Phylloxera louse was not resistant to the AxR1 rootstock. This rare form of Phylloxera was able to build up its numbers on the weakened AxR1 rootstock. Over time a population surge of the rare form of Phylloxera was experienced that led to the mass failure of all the AxR1 rootstock.

Vintners were naturally upset by this news. The fact that most vineyards had been re-developed by supposedly Phylloxera resistant rootstock meant that most of California faced a new epidemic. Equally upsetting was the fact that the fault of the problem was in human error advocating the use of AxR1 rootstock.

Analysis of the problem left very few solutions. Pesticide control was entertained, but just like in the major Phylloxera outbreak during the 1860s it was found that pesticides only retarded the louse. Pesticides could not be counted on to eliminate the Phylloxera louse. The only solution left to the vintners in California was to rip up the susceptible vines and start over. Rather than make the same mistakes with inferior rootstock, the University of California's College of Agriculture thoroughly researched rootstock solutions for Phylloxera.

Research into other areas of the biology of Vitis also assisted in combating the Phylloxera louse. Large-scale research into the Vitis genome had begun in earnest by the early 1990s. Continued research into all areas of the vine will provide solutions for future diseases and pests. In the present, the adoption of an appropriate Phylloxera resistant rootstock has once again successfully checked Phylloxera's conquest of the California wine industry.

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