Cultural Control of Phylloxera in Existing Vineyards by Root System Conversion
Root system conversion methods were evaluated at the White Hills Vineyard near Santa Maria, CA during the 1993 season. The study consisted of two experiments which utilized Gewurztraminer and Chardonnay in separate locations. Root system conversion treatments included inverted side grafting using cuttings, approach grafting using rootings and an ungrafted control. The Chardonnay experiment also investigated the suitability of selected rootstocks for root system conversion. Freedom, Harmony, Teleki 5C, Teleki 5A, Kober 5BB, and Couderc 1613 rootstocks were used in these experiments. Regrafting of vines not previously successfully converted was done in February 1993. Periodic inspections of the plots were made during the growing season. Graft union formation, rootstock growth, and vine growth were assessed during these inspections. Yield data were collected for Chardonnay when the vines were harvested on September 16, 1993. Gewurztraminer vines were harvested and yield data collected on September 30, 1993. Berry samples were collected at harvest and fruit composition determined. Gewürztraminer and Chardonnay graft unions were assessed (%conversion) on April 9, 1994 and June 2, 1994, respectively. Approach grafting increased the percentage conversion for Chardonnay vines. Approximately 80% of vines have been successfully converted. For Gewurztraminer, the percentage conversion remained approximately the same. We observed that a number of rootstocks died between the 1992 and 1993 seasons which had a negative impact on percentage conversion. Root system conversion method and rootstock had little effect on vine performance.