The art of protecting grapevines low temperature injury

Frost protection or protecting plants from cold temperatures where they could be damaged must be a consideration in vineyard planning. Cold protection events commonly occur during “radiation” frost conditions when the sky is clear, there is little wind and strong temperature inversions can develop. These conditions can happen during spring, fall or winter when it is necessary to keep canes, buds, flowers, small berries, or foliage above “critical” temperatures. The best frost protection technique is always good site selection. Use of water for frost protection in V. vinifera blocks is often not recommended when it is necessary to carefully manage soil water levels. Under-canopy sprinkling systems are usually not an option. Wind machines or “fans” rely totally on the strength of the temperature inversion for their effectiveness in warming the vineyard and may also be helpful in pushing cold air out of a vineyard. The placement of multiple wind machines must be carefully coordinated to maximize the areal extent and net effectiveness. Currently available fossil fuel-fired (oil and propane) heaters can be a big asset in frost protection activities, but are very inefficient and costly to operate. While there is no perfect method for cold temperature protection, quite often combinations of methods are advantageous. Wind machines have been found to work well with properly placed fossil fuel heaters and is probably the most appropriate combination for winter time cold protection in vineyards. A well-maintained and calibrated frost monitoring (thermometers and alarms) network will always be required. Knowledge of the current critical temperatures and the latest weather forecast for air and dew point temperatures are important because they tell the producer if heating may be at any stage of development and how much of a temperature increase should be required to protect the crop.