Effect of timing and intensity of summer pruning on vegetative and

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 2

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

3

Plant material  Two cultivars  ‘Emerald’ and ‘Jewel’

 Six year old plants  Commercial cultural

practices  PSREU – Citra, FL 4

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 www.caes.uga.edu 5

Treatments Unpruned

30%

60%

6

Vegetative traits  Canopy volume  Regrowth

 Condition of fall foliage  Time of defoliation

 Leaf spot 7

Vegetative traits  Incidence and severity

of Stem Blight

8

Reproductive traits  Re-growth shoots collected to assess timing

of flower bud initiation – Late summer until defoliation

9

Reproductive traits  Harvest  Period  Yield

 Fruit quality  Total soluble solids

picturesbychristopher.wordpress.com

 Titratable acidity  Firmness  Average berry weight

Labmate-online.com

10

RESULTS TO DATE

11

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

12

Regrowth volume - Emerald

13

Flower bud initiation  Important to:  Develop management strategies to enhance

flowering  Regulate fruit load  First sign of transition detectable

14

Flower bud initiation

15

Flower bud initiation

16

Flower bud initiation  No differences between treatments  Emerald – Sep 8th

 Jewel – Oct 20th

17

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 18

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

19

Stem blight  Jewel was not affected  No differences among treatments in

Emerald

20

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

21

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

22

Yield - Jewel

23

Yield - Jewel

24

Acknowledgements  Dr. Darnell and Dr. Williamson  Dr. Olmstead and Dr. Harmon

Florida Department of Agriculture and Consumer Services 25

Thank you!

26