The Problem Managing Crop Load on Size Controlling Rootstocks Lynn E. Long Oregon State University

• Perfect bloom weather • Right conditions • Healthy or stressed • Even Mazzard can overset

The Problem • Compounded with dwarfing rootstocks • No longer occasional problem • With improper management 5th leaf trees can overset

The Problem • Leading grower commented during tour that dwarfing rootstocks in Chile were huge failure due to oversetting

The Problem • At year’s end made statement that his orchard would not plant more dwarfing rootstock due to fruit size problems

The Problem • • • •

Dwarfing rootstocks Oversetting Small fruit size Are not automatic

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A compilation of fruit size and tree yield on 4th through 6th leaf ‘Bing’ trees grown on several rootstocks Rootstock

6th leaf trunk area cm2

Mazzard

152.3 35.3

G5

93.2

Cumulative 20mm yield kg

22mm

24mm

26mm+

1.4

22.2

32.0

44.4

49.9

1.4

19.1

30.3

49.2

G6

156.9 56.8

0.4

15.2

36.3

48.2

G 12

114.5 57.2

0.9

17.3

33.7

Sweetheart/Gi6 Trial • 8th leaf 76% 9 row (30 mm) and larger • 9th leaf 84% 9 ½ row (28 mm) and larger

48.1 Data by T. Facteau

Proper management is key • Size controlling rootstocks such as Gi 6 and 12 can grow high quality fruit • We need to learn to properly manage this new technology

Benton/Gi 6

Managing Mazzard Trees Precocity

Low

Pruning time

Dormant or summer

Pruning

Thinning cuts

Fruiting strategy Increase

Operation

Mazzard

Gisela

Precocity

Low

High

Pruning time

Dormant or summer

Dormant

Pruning cuts

Thinning

Heading

Fruiting strategy

Increase

Decrease

Vigor management Reduce

Maintain high

Orientation of fruiting wood

Mostly horizontal

Upright

Branch renewal

5 years

5 years

Vigor management

Reduce

Orientation of fruiting wood

Mostly horizontal

Branch renewal

5 years

The Future • Unless we learn how to properly manage productive rootstocks such as Gisela, the future of these rootstocks is questionable.

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What Effect Does Crop Load Have on Carbon Allocation for Growth? Year:

2000

Leaf population:

Fruiting spurs

13CO

2001

2002

Non-fruiting spurs

Current growth

13C

Movement From the Non-Fruiting Spur Leaves

2

32.5%

Lower Fruit

Upper Fruit

Lower Shoot

Upper Shoot

Crop Load Effects on 13C Movement From NFSpur Leaves to Fruit (Stage 3)

13

% C-Partitioned to Fruit

a

Distal LowerFruit Fruit

80

ab

Upper Fruit Proximal Fruit

70

a

60 50

bc

40

ab

30 20

bc

10 0

140140 cm2/fruit (Low)

3.9%

0.2%

~95% of C was partitioned to fruit, 5% to shoot Ayala and Lang 2004

Ayala and Lang 2004

90

63.3%

752/fruit 75 cm

40 2/fruit 40 cm

How to prevent overcropping • Pruning • Hand thinning blossoms or spurs • Chemical blossom thinning • Chemical fruit thinning • Hand fruit thinning

Leaf Area/Fruit ratio (cm /fruit) High) (Leaf Area basis) Crop Load 2

Ayala and Lang, 2004

Operation

Gisela

Precocity

High

Productivity

High

Simple 3 Step Process Timing

Technique

Purpose

1st dormant season on Tip all new growth

Reduces future crop

Reduces current crop

Vigor management Maintain high

2nd dormant season Stub 20% of fruiting after significant fruiting branches back each year

Pruning timing

Dormant

Dormant season, each Thin shoots at tree top Allows light year to single branch penetration

Branch renewal

5 years

Fruiting strategy

Reduce

Pruning cuts

Heading

3

Step 1

Tipping Response

• Dormant season • Remove ⅓ to ½ of last years growth • Tip all branches • Reduces future crop

44 DAFB Beginning Stage III

Fruit : 25% final size

55%

Shoot: 16 leaves

Current Season Carbon Sources Year

2001

Leaf population

Fruiting spurs

13CO

2

2002

2

16%

2003

Non-fruiting spurs

13CO

29%

Current season shoot 13CO

Fruiting spur leaves

56 DAFB Mid Stage III

Fruit : 58% final size

38%

Shoot: 18 leaves

NonNon-fruiting spur leaves

Shoot leaves

34% 28%

2

Fruiting NonNon-fruiting spur leaves spur leaves

75 DAFB Late Stage III

Fruit 92%g final size Fruit:: 4.2

Shoot leaves

48%

Shoot: Shoot:22 16leaves leaves

28%

Ayala and Lang, 2004

Fruiting spur leaves

NonNon-fruiting spur leaves

24%

Shoot leaves

Ayala and Lang, 2004

Unpruned

Pruned 1 year Bing/Gisela 5

Bing/Gisela 5 Year 1 – vegetative growth Year 2 – vegetative growth Year 3 – vegetative & fruit growth

Matthew Whiting, WSU

Assumptions: Assumptions: 7 lvs/spur 6 fruit/spur 60 cm annual growth 1 node per 2.5 cm 5 leaves/fruit neces.

7 lvs/spur 6 fruit/spur 60 cm annual growth 1 node per 2.5 cm 5 leaves/fruit neces. M. Whiting, WSU

Year 3 Leaf:Fruit

Year 3 Leaf:Fruit

4.7 leaves/fruit

2.5 leaves/fruit Year 4 Leaf:Fruit

1.8 leaves/fruit

Year 4 Leaf:Fruit • Manage crop load in year 1 (shoots)

2.1 leaves/fruit

4

Pruned 2 years

Step 2

Bing/Gisela 5

• Renewal Pruning • Dormant Season • Stub back 20% of all fruiting wood each year • Leave 6-8 cm stubs • Reduces current seasons crop • Renews spurs

Year 3 Leaf:Fruit 4.4 leaves/fruit Year 4 Leaf:Fruit 3.5 leaves/fruit M. Whiting, WSU

• Manage crop load in year 1

Step 2 ½ • Long unbranched wood with no terminal growth must be headed in order to stimulate new growth.

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