Can row covers be used to protect my grapes during a spring freeze?
Spunbon polyester row covers, such as Agribon™ or Reemay®, act as blankets which slows the rate of heat loss from the soil. Row covers protect plants by trapping heat released from the soil and are available in several weights and dimensions. The heavier the row cover, the more protection it provides but the less light is transmitted. While very common in vegetable production, they are very cumbersome to place over high-density orchards and vineyards due to wind. A 0.5 oz/yd2 cover will provide 2°F to 4°F of protection outside. They must be closely monitored so that temperatures do not get too warm during the day. If it is a sunny day, expect to have to remove the cover.
This has been tried over trellis systems using bird netting machines. The wind prevents you from being able to actually put the row covers over the row. This is not an effective (practical) method of preventing late spring freeze damage to plants.