Cultural Control of Phylloxera in Existing Root Systems
Root system conversion methods were evaluated in small research blocks at the White Hills Vineyard near Santa Maria, CA and the Meridian Vineyard near Paso Robles, CA during the 1992 season. Larger scale commercial blocks were evaluated at the previously mentioned vineyards as well as the Douglas Vineyard near Santa Ynez, CA, the Cat Canyon Vineyard near Los Alamos, CA, and the Sierra Madre Vineyard near Santa Maria, CA. Varieties used in these experiments were Gewurztraminer (White Hills), Chardonnay (Cat Canyon, Douglas, Sierra Madre, and White Hills), Cabernet Sauvignon (Meridian) , and Syrah (Meridian). Root system conversion treatments included inverted side grafting using cuttings, approach grafting using a rooting, interplanting between existing vines using a benchgraft, and an ungrafted control. In certain experiments, the suitability of selected rootstocks for root system conversion was tested using inverted side grafting (cutting). Freedom, Harmony, Teleki 5C, Teleki 5A, Kober 5BB, and Couderc 1613 rootstocks were used in these experiments. Grafting was done in February 1992 by Ken Coates, Coates Grafting, East Wenatchee, WA. Periodic inspections of the plots were made during the growing season. The extent of graft union formation was subjectively assessed during these inspections. Data on the cost of grafting and after-grafting care in commercial scale blocks were collected by Hampton Farming Company personnel. Yield data for Gewurztraminer was collected when vines were harvested on September 9, 1992. Syrah vines were harvested and yield data collected on September 11, 1992. Harvest of Chardonnay vines occurred on September 25, 1992. Berry samples were collected at harvest and fruit composition determined. Percentage take was measured on December 2-4, 1992. Chardonnay and Gewurztraminer vines were pruned during February 1993. Approach grafting produced the highest %take. The percentage take obtained for inverted side grafting using cuttings was extremely low as in 1991. This method of root system conversion is not recommended for further testing. Root system conversion method and rootstock had little effect on vine performance. Economic analysis of approach grafting indicated that it would cost approximately $5,210 / acre to achieve 100%conversion during a 5 year period with a 76%initial take. This is a conservative and high estimate. Factors influencing the estimated cost of root system conversion by approach grafting were vineyard density (83 0 vines/A), the initial %take, and the cost of grafting which was relatively high at $3.00/vine.