Some of you may have already conducted leaf removal in your vineyards, but some of you are now getting into the early fruit development stage where leaf removal is considered more of the ‘standard’ time point. See some of lovely pictures of some fresh leaf removal from Bill Cox.
Q: Why remove leaves?
A: Fruit-zone leaf removal can be an excellent practice to increase fruit quality by improving flavor compounds, color, bud fertility, decreasing TA, pH, and potassium, and reducing some of the more vegetative aromas in some varieties. Additionally, more sun exposure, increased air flow, and better spray penetration can all help reduce disease pressure (for many diseases, though maybe not sour rot) on the fruit as well!
Q: When to remove leaves?
A: Often, leaf pulling is conducted shortly after bloom and fruit set while the berries are still small (BB-sized). This is often thought to help with sunburn issues on the fruit. However, this can also be based on the ideal world where you can finish everything at the exact time you planned and the plants and weather cooperate – if anyone learns that secret to doing that all the time, please share! Some research (including UGA Annie Vogel’s leaf removal study) suggested that removal pre-bloom can reduce fruit yield and quality. Other work suggests that leaf removal after veraison also increases sunburn risk. So, I would suggest that now you start after bloom and finish as soon as you can, but no later than veraison.
Q: How many leaves to remove?
A: This will depend on the vigor of your vines – you want to make sure that there are still enough leaves to support the growth of the fruit and provide winter reserves for the vine. Some research indicates that 2-3 leaves around the fruiting zone is sufficient. In the SE, I’ve even seen 5-6 leaves removed. In areas with high light and high heat, generally you would want to remove the leaves on the morning side of the canopy. Annie Vogel’s work did not show a difference based on the side of the canopy pull occurred though.
Q: Do we have big sunburn issues on GA Grapes?
- This one is a question for ya’ll! I have not heard from anyone yet about too many issues with berry sunburn – though potentially because this is still too early for this to be a concern. Maybe as we progress later in the season, I will hear about it more? Let me know what your experience has been! While some leaf removal experiments were done here several years ago, there are more experiments we can do in this arena, especially if there are fewer sunburn concerns.
- Nathan Eason’s (White Co. Extension) reflects on observations in VA https://site.extension.uga.edu/viticulture/2017/07/reflections-on-leaf-removal-practices-and-trellis-systems-from-recent-virginia-trip/
- Annie Vogel’s UGA Master thesis – https://esploro.libs.uga.edu/esploro/outputs/graduate/EVALUATING-LEAF-REMOVAL-METHODS-EFFECTS-ON-CROP-YIELD-DISEASE-MANAGEMENT-AND-PRIMARY-AND-SECONDARY-METABOLITES-IN-BUNCH-WINE-GRAPES/9949365737602959
- John Scaduto’s (Rabun Co. Extension) comments on mechanical leaf removal https://site.extension.uga.edu/viticulture/2017/08/mechanical-leaf-removal-considerations-for-vineyards/
- June 24th – GWP New Grape Grower Symposium! Carrollton, GA – Registration now open$85 – https://www.georgiawineproducers.org/event-5284992
- July 20th – GiESCO Professional Day – Applied Viticulture Presentations VIRTUAL $75 or in- person ($300 or $450 with banquet) in Ithaca, NY. https://cals.cornell.edu/giesco