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Vineyard frost protection considerations

The moderate winter temperatures may result in an early bud break in vineyards. Frost protection may thus be of concern for many industry members throughout Georgia and the southeastern US.

Please see this link for our extension bulletin on frost protection considerations.

https://secure.caes.uga.edu/extension/publications/files/pdf/B%201490_1.PDF

Please also see this link (from eXtension) on frost injury and avoidance in vineyards.

The persistent rain may have precluded the ability for many to get out and prune as often as desired. Delayed pruning may thus be a topic of particular interest.

Our preliminary data showed that leaving five-bud spurs and “delay pruning” to two-bud spurs when the apical (top) buds were at bud break resulted in 13 to 50% lower bud break incidence in retained, lower count buds when compared to final pruning to two-bud spurs in the dormant period. (Note: bud break was evaluated in Merlot and Chardonnay near the average frost free date at the research vineyard location). When compared to final pruning to two-bud spurs in the dormant period, leaving five-bud spurs and “delay pruning” to two-bud spurs when the apical (top) buds were at bud break reduced crop yield from retained, lower count buds by 0.4 to 1.1 tons/acre. “Delay pruning” to two-bud spurs when apical (top) bud positions were at 1.5″ shoots reduced crop yield from retained, lower count buds by 1.8 to 2.8 tons/acre when compared to dormant pruning to two-bud spurs in the dormant period.

The take-home from this preliminary data suggests that delayed pruning may not be worth implementing on sites / blocks with low frost risk. Delayed pruning may also not be a good option if labor is not available to implement the final prune in a timely fashion to prevent a large reduction in crop yield from the lower, retained buds. However, in years when a frost event occurs, delayed pruning when apical (top) buds are at bud break may be a fiscally rewarding practice relative to dormant pruning to two-bud spurs in the dormant period. Thus, one must know the history of frost threat at their site and understand the risk/reward for implementing delayed pruning. This data was collected in Merlot and Chardonnay in one season; results may differ in other cultivars and in future seasons of data collection. (Note: the interpretation of this data assumes that the lower percentage of bud break observed in the delayed pruning treatments would also mean that frost injury would be avoided if a frost event occurred on the date that bud break data was assessed. However, since a frost event did not occur at the research vineyard, there is no way to know exactly how crop yield would have been affected by treatments in the case of a frost event).

As noted in the attached extension publication (above), judicious site and cultivar selection may be the most effective ways to reduce frost threat.