I wanted to briefly share some data from our delayed pruning experiment now that pruning is the primary vineyard focus for many industry members… Hopefully this will provide some “food for thought” as y’all consider your delayed pruning strategies this dormant season. I apologize in advance for the lack of tables and figures – they wouldn’t copy into the post in a fashion that blog subscribers could read legibly.
A full presentation on delayed pruning will be given at the Georgia Wine Producers (GWP) Conference at Chateau Elan on February 5th. You can register for the GWP Conference here: www.georgiawineproducers.org/2019-annual-meeting/
TREATMENTS: We evaluated the effect of retained bud number on dormant spurs (canes?) on bud break delay and crop yield in Chardonnay. I put “canes” in parentheses with a question mark because I do not know the point at which “spurs” are called “canes”… do spurs become canes at 5 buds? 7 buds? 10 buds? I’m not sure. Our treatments were FINAL (two-bud spurs), 4 (four-bud spurs), 7 (seven-bud spurs/canes…), 10 (10-bud spurs/canes), and NO (dormant canes hedged one foot above top catch wire). FINAL was pruned in the dormant period while FOUR, SEVEN, TEN, and NONE were delay pruned on April 5th, when bud break was roughly 50% across all treatments.
RESULTS: All delayed pruning treatments delayed average bud break on several dates relative to FINAL – up until April 26th, when all buds were broken in all treatments. On April 12th, the date closest to the average frost-free date at the vineyard site, NONE and TEN had an average of 36% fewer buds broken relative to FINAL, while FOUR and SEVEN had an average of 26% fewer buds broken relative to FINAL. NONE reduced crop yield by 33% relative to FINAL, while FOUR, SEVEN, and TEN reduced crop yield by 3%, 12%, and 15% relative to FINAL, respectively. Fruit composition was not affected by treatment.
Practical take home: Know your site. Based on our data thus far, you must weigh your risk and reward with delay pruning as bud break can be delayed but crop yield can also be reduced. If your site / cultivar / block is at a high risk of springtime frost on a perennial basis, it might be worthwhile to consider delay pruning to seven- to 10-bud spurs so that bud break delay is optimized and drastic crop yield penalties are not incurred. If your site has a medium springtime frost risk, maybe consider delay pruning to four-bud spurs to effectively delay bud break with very little crop yield penalty. Consider delayed pruning in early bud-breaking cultivars that are at greatest springtime frost risk, as final pruning takes time and represents an added vineyard task as the season gets underway. Note – that this data is from one cultivar (Chardonnay) grown at one site (Dahlonega, GA) in one vintage (2018). Results may thus vary in other situations. We do plan on executing this trial in 2019 as well.
Please also note that this trial did not evaluate the optimal timing to make the final cut. We made the final cut on the same date across all treatments so that it would not be a factor that affected results. Our chosen date (roughly 50% bud break) may have been too late to avoid the crop yield reductions observed; if we had made the final cut 10 days before would we have seen the same crop yield reduction? would we have seen the same bud break delay?. In 2019, we do plan on evaluating the “final cut timing effect” in tandem with the herein evaluated “bud number effect”. At the termination of our projects, we hope to have refined delayed pruning recommendations for our industry that will optimize bud break delay without negatively effecting crop yield and fruit maturity.
Stay tuned. And get pruning!