Phylloxera-Resistant Rootstock Trials in the Coastal Valleys of California

¹ Department of Viticulture and Enology University of California, Davis

Grape rootstock investigations during the past fifty years by the United States Department of Agriculture and the Department of Viticulture of the College of Agriculture have provided a basis for selection of a limited number of rootstocks for the cooperative field trials which have been considered in this report.

A series of field trials was evolved in order to evaluate the performance of a few chosen experimental rootstocks with a number of fruiting varieties over as wide a range of environmental conditions as possible in the north coastal vineyards of California.

A survey of the data collected has shown that the most popular phylloxera rootstock used commercially, Rupestris St. George, is not the most suited under the conditions to which it was tested, whereas, the experimental stock, A x R^#I, is generally the most vigorous and productive of the array of stocks under consideration.