Issue link: http://read.dmtmag.com/i/51841
VINEYARD PREVENTING DAMAGE The best methods to reduce frost risk and prevent crop loss are through vineyard site selection, planting later-growing varieties in frost-prone locations, and the use of sprinklers or wind machines dur ing f rost events. Researching historical spring temperature data and weather records for specific locations can provide a guide for vineyard siting, design and var iety choices for planting. Ongoing monitoring with vine- yard weather stations and visual observations can provide guidance for modifying vineyard design, regrafting rows or blocks to later-bud- ding varieties, and effec- tive placement of frost protection systems. Frost damage commonly occurs in low-lying areas where cold air set- tles, and in areas where wind and air movement are blocked by obstruc- tions such as trees, hills, fences and/or buildings. Locating and ori- enting vine rows to facilitate air flow can reduce settling of cold air. Varieties that begin growth and bud early in the season can be vulnerable to frost injury, such as chardonnay, gewurztraminer and viognier. Some varieties, such as sylvaner – more commonly planted outside of California – can recover better than others after frost. In the Central Coast frost of 2011, there were reports of great- AT A GLANCE where early-budding varieties had significant frost damage. PASSIVE PROTECTION Research shows that vineyard Spring frost damage to grapevines is a danger any time after bud break. Good site selection, planting later-budding varieties and late pruning can help prevent spring frost damage. Removing vine growth (damaged or living) before the end of the frost season is usually not recommended. New research on spring weather conditions in California vineyards will evaluate viability of wind machines as alterna- tives to sprinkler frost protection. er damage to primary buds and shoots of chardonnay, pinot noir, viognier and roussanne. Reports by individual growers cited yields of viognier of just a half-ton per acre, down from a normal average of 5 tons/acre. Some cabernet sauvi- gnon vineyards also reported yields of just 0.5 ton/acre. Later-budding varieties such as syrah and petite sirah were undamaged in locations ground can best retain heat from solar radiation on spring days when soil is bare, firm and moist. By storing heat energy, the soil can then contribute to higher air temperatures on cold nights. Vineyards man- aged with cover crops in frost-prone locations must balance the risk of frost with the benefits of maintaining cover crops. Mowing weeds or cover crops close to ground level, and avoiding soil tillage in spring, can help increase soil tem- peratures, particularly in flat, low-lying locations exposed to cold temperatures. Late-season pruning, or double pruning, can reduce the time frame for frost exposure by delaying bud break up to two or more weeks, depending on location and season. Tablas Creek Vineyard, in a frost- prone location in Paso Robles, employs a strategy of pruning its latest-growing varieties first and pruning early-growing varieties last. WWW.VWM-ONLINE.COM JAN - FEB 2012 VINEYARD & WINERY MANAGEMENT 55