Cultural Control of Phylloxera in Existing Vineyards
Root system conversion methods were evaluated at the White Hills Vineyard near Santa Maria, CA and the Meridian Vineyard near Paso Robles, CA during the 1991 season. Varieties used in these experiments were Gewurztraminer (White Hills), Chardonnay (White Hills), and Syrah (Meridian). Root system conversion treatments included inverted side grafting using a cutting, approach grafting using a rooting, chip budding on the rootstock, interplanting between existing vines with a benchgraft and an ungrafted control. In certain experiments, rootstocks were evaluated using the inverted side grafting (cutting) and chip budding on rootstock methods. Harmony, Freedom, Teleki 5C, Couderc 3309, Salt Creek, Dogridge and Richter 110 rootstocks were used in these evaluations. Grafting was done in February 1991 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 and rooting of cuttings were subjectively assessed during these inspections. Yield data for Chardonnay and Gewurztraminer were collected when the vines were harvested on October 7, 1991. Yield data were not available for Syrah vines. Berry samples were collected at harvest and fruit composition determined. Percentage take was measured on December 9-10, 1991 for Chardonnay and Gewurztraminer and on January 16, 1992 for Syrah. Vines were pruned and prunings weighed during January and February 1992. The %take obtained during the 1991 season was low for the inverted side graft (cutting) and approach graft methods. This result was probably influenced by the rootstock wood used in grafting. Little suitable rootstock wood was available during 1991. Rootstock rootings or cuttings used for the inverted side graft or approach graft should have at least 6-8″ of 1/4″ minimum diameter cane. When rootstock wood meeting this criteria was used, inverted side grafting and approach grafting were successful. Chip budding on roots was a uniform failure and cannot be recommended for further evaluation. Root system conversion methods and rootstocks had almost no effect on vine performance. Yield and pruning weight were not significantly affected by treatment at any of the locations in the study. It is likely that differences in vine performance will become evident when the “new” rootstock becomes predominant over the existing root system.