University of Florida
Horticultural Sciences Department
Effect of timing and intensity of summer
pruning on vegetative and reproductive
traits of southern highbush blueberry
Al Kovaleski
September, 2013
Blueberry summer pruning
 No removal of flower buds
 Long growing season in FL
 Pruning promotes increased vigor
 More support for reproductive
structures
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Objectives
Determine the effects of timing and severity
of summer pruning:
Vegetative traits:
• Plant volume
• Regrowth
• Timing of defoliation
• Incidence of leaf spots
• Incidence and severity of
stem blight
Reproductive traits:
• Flower bud initiation
• Fruit set
• Yield
• Quality of fruit
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Plant material
 Two cultivars
 ‘Emerald’ and ‘Jewel’
 Six year old plants
 Commercial cultural
practices
 PSREU – Citra, FL
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Treatments
 No summer pruning control
 Prune 30% early June
 Prune 30% mid-July
 Prune 30% early June+tip
 Prune 60% early June+tip
 Detailed hand pruning control
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Treatments
Unpruned
30%
60%
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Vegetative traits
 Canopy volume
 Regrowth
 Condition of fall foliage
 Time of defoliation
 Leaf spot
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Vegetative traits
 Incidence and severity
of Stem Blight
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Reproductive traits
 Re-growth shoots collected to assess timing
of flower bud initiation – Late summer until
defoliation
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Reproductive traits
 Harvest
 Period
 Yield
 Fruit quality
 Total soluble solids
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 Titratable acidity
 Firmness
 Average berry weight
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RESULTS TO DATE
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Canopy volume - Emerald
Treatment
Non-pruned
Hand pruned
30% June
30% June+tip
60% June+tip
30% July
Winter volume
(m3)
1.26a
1.06b
1.01bc
0.91c
0.68d
0.91c
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Regrowth volume - Emerald
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Flower bud initiation
 Important to:
 Develop management strategies to enhance
flowering
 Regulate fruit load
 First sign of transition detectable
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Flower bud initiation
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Flower bud initiation
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Flower bud initiation
 No differences between treatments
 Emerald – Sep 8th
 Jewel – Oct 20th
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Leaf spots - Jewel
Leaf spot incidence (%)
2011
Treatment
2012
17 Nov
1 Dec
21 Dec
25 Oct
8 Nov
23 Nov
11 Dec
Non-pruned
70.0 a
78.8 a
57.6 ab
38.3 a
81.7 a
88.3 a
97.5
Hand pruned
33.3 b
25.4 b
54.3 ab
31.7 a
56.7 bc
78.3 bc
96.7
30% June
43.3 ab
48.8 ab
50.9 b
35.0 a
61.7 b
83.3 ab
95.0
30% June+tip
36.7 b
48.8 ab
64.3 ab
26.7 ab
53.3 bc
81.7 abc 96.7
60% June+tip
36.7 b
52.1 ab
84.3 a
15.0 b
53.3 bc
73.3 c
100.0
30% July
66.7 a
82.1 a
67.6 ab
15.8 b
41.7 c
78.3 bc
94.2
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Defoliation - Jewel
Defoliation (%)
2011
Treatmentz
2012
1 Dec
21 Dec
25 Oct
8 Nov
23 Nov
11 Dec
Non-pruned
15.0 aby
37.4 ab
21.7 a
27.5 a
68.3 a
95.0 a
Hand pruned
0.0 c
30.8 b
4.2 ab
13.3 b
31.7 b
80.0 abc
30% June
6.7 bc
27.4 b
10.0 ab
10.0 b
36.7 b
81.6 abc
30% June+tip
5.0 bc
34.1 ab
6.7 ab
11.7 b
36.7 b
86.6 ab
60% June+tip
5.0 bc
52.4 a
0.0 b
6.7 b
25.0 b
71.6 c
50.8 a
4.2 ab
13.3 b
35.0 b
80.0 bc
30% July
20.0 a
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Stem blight
 Jewel was not affected
 No differences among treatments in
Emerald
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Berry quality
 Average weight - Jewel
 Reduction in the 60%+tip
 2g  1.5g
 Others averaged 1.7g
 pH, acid and sugar content, anthocyanins,
firmness
 No differences
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Yield - Emerald
Treatment
Yield (lbs)
Periods
2
3
Total
1
4
Non-pruned
14.4 NS
5.0 a
6.2 NS
2.2 NS
0.7 NS
Hand pruned
13.4
3.7 ab
6.4
3.4
1.1
30% June
12.6
3.1 ab
6.8
3.4
0.7
30% June+tip
14.6
3.7 ab
6.9
3.2
0.6
60% June+tip
12.6
1.5 b
5.5
3.6
1.1
30% July
13.1
2.0 b
5.3
2.4
1.0
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Yield - Jewel
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Yield - Jewel
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Acknowledgements
 Dr. Darnell and Dr. Williamson
 Dr. Olmstead and Dr. Harmon
Florida
Department
of Agriculture
and Consumer
Services
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Thank you!
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