penn state research trials on leaf removal · 2020. 6. 12. · cluster weight (g) # berry/ cluster...
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Effects on bunch rot
Effects on yield
Effects on fruit composition
Penn State research trials on leaf removal
Bryan Hed – Grape pathologist
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Penn State research trials on leaf removal across PA
• VarietiesoRiesling
oPinot noir
oPinot grigio
oGrüner Veltliner
oVignoles
• Multi-year studies
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Can leaf removal be mechanized while maintaining the same benefits of manual application?
Pulsed-air leaf remover (Collard, Bouzy, France)
Tractor speed: 1.4 mphHead speed was set at 850 rpm
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RieslingControl Hand leaf removal Mechanical leaf removal
Leaf area mechanically removed with the machine was on average 51% of that removed by hand
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Control vines, no-leaf removal
Riesling vines at harvest
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Both hand and mechanical leaf removal improved fruit sunlight exposure
Hand leaf removal Mechanical leaf removal
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Leaf removal trials in Erie county
Photo credit B. Hed
Blueline Deleafer, Blueline Manufacturing Company Inc, Yakima, WA
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Pinot Grigio (2018) – Erie county
Photos credit B. Hed
Control vines, no-leaf removal Mechanical leaf removal
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Effects on bunch rot
Effects on yield
Effects on fruit composition
Penn State research trials on leaf removal
Bryan Hed – Grape pathologist
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Carbohydrate limitation
Can reduce fruit set (percentage of flowers that become fruit)
Decrease the number of berries per cluster and cluster compactness
Removing basal leaves pre-bloom
‘Early’ leaf removal (pre-bloom/ trace bloom) affects cluster morphology
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The compactness of the cluster favors the colonization and spread of bunch rot organisms within the cluster
berry-berry contact
Berry number
Early leaf removal
Spread of bunch rot
No-early leaf removal
Early leaf removal
Photo credit: M. Smith
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Pre-bloom 4 (2.12 t/acre) Pre-bloom 8 (1.17 t/acre) Post-fruit set 6 (3.52 t/acre)
Timing (and extent) is everything…
Crop yield can be affected by the number of leaves removed before bloom
Cabernet Sauvignon (VA)
Source: Cain Hickey
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Effects on bunch rot
Effects on yield
Effects on fruit composition
Research trials on leaf removal
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Pinot Grigio (2017 and 2018)
Treatment Incidence of rot infection
(% clusters)
2017 2018
Control - no leaf removal 44.0 30.0
Hand leaf rem. – pre-bloom 8.5 4.0
Mechanical leaf rem. – pre-bloom 13.0 9.0
Mechanical leaf rem. – fruit set 16.0 9.0
Incidence = Percentage of clusters with bunch rot
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Treatment Severity of bunch rot
(% cluster area )
2017 2018
Control - no leaf removal 11.6 7.5
Hand leaf rem. – pre-bloom 1.2 0.9
Mechanical leaf rem. – pre-bloom 3.0 2.7
Mechanical leaf rem. - fruit set 2.2 1.9
Severity = percentage of the cluster’s area affected
Pinot Grigio (2017 and 2018)
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Control Hand-LR Mechanical-LR
Photo credit: B. Hed
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Cluster weight (g)
# Berry/cluster
Severity of bunch rot
(% area)
Control - no leaf removal 127.8 97.8 11.59
Hand leaf rem. – pre-bloom 108.4 73.2 1.23
Mechanical leaf rem. – pre-bloom 107.8 74.5 2.95
Mechanical leaf rem. - fruit set 127.9 101.4 2.17
→ Leaf removal before bloom: Vines have smaller and less compact clusters → Leaf removal reduced bunch rot regardless of timing or method
Pinot grigio (2017)
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Cabernet Sauvignon Botrytis – in VA
Botrytis incidence (%)
No leaf removal 18.5
Pre-bloom - 4 0.0
Pre-bloom - 8 0.0
No leaf removal 28.8
Post-fruit set - 6 6.4
Hickey et al. (2018) - Catalyst
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Effects on bunch rot
Effects on yield
Effects on fruit composition
Research trials on leaf removal
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Treatment Titratable acidity
(g/L)2017 2018
Control - no leaf removal 5.4 6.0
Hand leaf rem. – pre-bloom 4.8 4.3
Mechanical leaf rem. – pre-bloom 4.8 4.9
Mechanical leaf rem. – fruit set 4.6 4.5
Pinot noir (2017 and 2018)
Fruit ripeness parameters →most consistent effect across studies was a reduction in TA
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Sugars and acids – Merlot in NC
Brix: TA ratio
TA (g/L)
No Leaf Removal 4.4 4.2
Leaf Removal 4.8 3.8
Chardonnay
High Brix: TALow Brix: TA
Source: Cain Hickey
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Anthocyanins – Cabernet Sauvignon in VA
Total grape anthocyanins (mg / g berry)
2013 2014 2015
NO 0.94 1.11 b 0.83 b
PB-4 1.00 1.22 a 1.00 a
PB-8 1.02 1.12 b 1.02 a
Hickey and Wolf (2018)
Total grape anthocyanins (mg / g berry)
2013 2014 2015
EAST 1.02 1.15 0.94
WEST 0.96 1.16 0.95
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Take home message
• Regardless of timing and method, leaf removal reduced bunch rot compared with no leaf removal
• Pre-bloom leaf removal should be judiciously used as it can result in crop reduction
• Basic juice chemistry: the most consistent effect of leaf removal was lower juice acidity
• Mechanized leaf removal mimicked most of the effects of the manual application
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Acknowledgments
Grower cooperators
Bryan Hed
Penn State Wine and Grape Team
Penn State Viticulture research lab
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