Presentation: The effects of defoliation timing and a comparison of ...

The effects of defoliation
timing and a comparison of
defoliation methods
Dr. Mark Krasnow
Senior Lecturer, EIT

Removal of leaves in the bunch
zone is a common practice in
cool climate growing regions
such as New Zealand

Removal of leaves in the bunch
zone is a common practice in
cool climate growing regions
such as New Zealand
• Increases exposure of fruit to
sunlight

Removal of leaves in the bunch
zone is a common practice in
cool climate growing regions
such as New Zealand
• Increases exposure of fruit to
sunlight
• Promotes airflow around
bunches

The timing of defoliation is an
important consideration

The timing of defoliation is an
important consideration
• If done too early, leaves can
regrow and require another
leaf removal

The timing of defoliation is an
important consideration
• If done too early, leaves can
regrow and require another
leaf removal
• If done too late, benefits of
fruit exposure may be
reduced

We tested 3 different timings of
defoliation

We tested 3 different timings of
defoliation
• Preflowering

We tested 3 different timings of
defoliation
• Preflowering
• At Set

We tested 3 different timings of
defoliation
• Preflowering
• At Set
• Prebunch closure

We tested 3 different timings of
defoliation
• Preflowering
• At Set
• Prebunch closure
At each timing the 6 bottom
leaves were removed by hand and
also using a leaf plucking machine

Gregoire® Sucker-cutter type defoliator

Leaf area measurement at
veraison to quantify regrowth
after defoliation
Data from Cabernet Sauvignon,
but similar in other varieties

Harvest yield (kg per vine)
In some varieties early leaf removal
reduces yield, while in others it has
no effect

Bunch compactness was measured
using the OIV 9-point scale

Bunch compactness
In general, early defoliation leads to
less compact bunches compared to
later or no defoliation

Rot severity
was
measured
using the
method of
Hill et al.
(2010)

Rot severity (% of area infected)
In some cases early defoliation
reduced rot severity, while in others
there was no effect or an increase

Effects on berry growth and
composition
• Defoliation timing had no significant
effect on berry weight in any of the
varieties tested

Effects on berry growth and
composition
• Defoliation timing had no significant
effect on berry weight in any of the
varieties tested
• Defoliation timing had no significant
effect on Brix, pH, or TA for
Chardonnay and Sauvignon blanc

Cabernet
Sauvignon
Merlot

Summary
• Preflowering, mechanised leaf removal
removes less leaf area than hand removal
of the 6 bottom leaves, whereas at set
and prebunch closure the two methods
remove a similar amount of leaf area

Summary
• Preflowering, mechanised leaf removal
removes less leaf area than hand removal
of the 6 bottom leaves, whereas at set
and prebunch closure the two methods
remove a similar amount of leaf area
• Lateral regrowth recovers the removed
leaf area from early defoliated vines, and
they have similar leaf area at veraison to
the standard prebunch closure treatment

Summary (Cont.)
• Preflowering defoliation, whether by hand
or machine, reduces yield and bunch
compactness in Chardonnay, Merlot, and
Cabernet Sauvignon, but not in Sauvignon
blanc

Summary (Cont.)
• Preflowering defoliation, whether by hand
or machine, reduces yield and bunch
compactness in Chardonnay, Merlot, and
Cabernet Sauvignon, but not in Sauvignon
blanc
• Rot results mixed

Summary (Cont.)
• Preflowering defoliation, whether by hand
or machine, reduces yield and bunch
compactness in Chardonnay, Merlot, and
Cabernet Sauvignon, but not in Sauvignon
blanc
• Rot results mixed
• Early defoliation had no effect on Brix, pH,
or TA of Chardnonnay and Sauvignon
blanc, and had only slight effects in Merlot
and Cabernet Sauvignon

Acknowledgements
EIT
Vineyard/Winery
Petra King
Robin Back
Rohan McGowan Nelson Wong
Jadmika
Larry Morgan
Tingting Zhang
Pete Cowley
Andrew Buo
Pete Gough
John Nuthalapati
Tony Smith
Karen Ball
Brookfield Vine Services
Melissa Annand Caine Thompson
Malcolm Reeves
LandWise
…And of course, you