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December 2015 WINES&VINES 83 WINE EAST GRAPEGROWING in the northern stretch of the area. Late-spring frosts can still be a concern for vines not planted on sites with relative elevation that encourages cold air drainage. Soils in the Southern Piedmont are classified as well drained, with ample red clay subsoil to hold moisture between rains. Although average annual precipitation ranges from 45 to 60 inches, drip irrigation is recommended due to hotter summer temperatures than experienced at dry-farmed sites in the Southern Blue Ridge. Domi- nant parent rock includes biotite, gneiss, schist, slate, quartzite, p h y l l i t e , a m p h i b o l i t e a n d granite. Soils generally range from loamy to clay in texture, with pH from 4.5 to 6.5, and can be shallow to very deep, and severely eroded in some instances. Vineyards planted on soils with either sandy clay loam or loamy clay surface soil (8-14 inches)—or clay loam to sandy gravelly clay loam subsoil over decomposing rock—are showing good production poten- tial. Common nutrient deficiencies in grapevine tissue include nitro- gen, phosphorous, magnesium and boron with occasional low potassium. Water erosion of shal- low surface soil remains a chal- lenge when developing and managing vineyard sites. Pierce's disease: the major challenge The major factor limiting produc- tion of bunch grapes in the South- ern Piedmont region is Pierce's disease (PD), a lethal disease that is endemic to the Southern Pied- mont and the Coastal Plains. PD is caused by the bacterium Xylella fastidiosa and vectored by xylem- feeding insects. In susceptible va- rieties, including V. vinifera, the bacteria clog the vascular tissue, causing drought-like symptoms and eventual vine death. The foothills of the Southern Blue Ridge in north Georgia have less risk of PD because of the colder winter temperatures at higher elevation. Studies by North Carolina State University (see "Blanc du Bois Takes Root" in the February 2012 issue of Wines & Vines) have shown that tempera- tures below 10° F, sustained for three or more days, may reduce survival of the PD bacteria. Warmer winter temperatures in recent years have increased PD pressure in some areas of the Blue Ridge foothills, making estab- lished vineyards a moving target for the disease. Given the increased pressure for PD in north Georgia, it was once difficult to imagine the ex- pansion of vineyard acreage in the Southern Piedmont. Muscadine grapes (V. rotundifolia) have long been planted in the South in part because of their resistance to PD. These grapes, with their distinc- tive aromas and flavors, have a following among both winemak- ers and local consumers. Recently, the adoption of sev- eral PD-tolerant hybrid bunch grape varieties has allowed the expansion of the wine industry in Natural Corks Champagne Corks Twinline Corks Bartops VISION Synthetic Corks G-Cap® Screw Caps Sales Representatives: Chris & Liz Stamp info@lakewoodcork.com lakewoodcork.com 4024 State Route 14 Watkins Glen, NY 14891 607-535-9252 607-535-6656 Fax PIONEER INNOVATOR PARTNER Four Pierce's disease-tolerant cultivars are evaluated on three training systems at the research and demonstration block at Trillium Vineyards in Bremen, Ga.