Pear mechanical pruning:

Bartlett 2015-2016

Sara Serra 15 June 2017, Wenatchee, WA

Project Title: Mechanical pruning in apple, pear and sweet cherry Funding agency: WTFRC

PI: Karen M. Lewis (WSU) Co-PI: Stefano Musacchi, Matthew Whiting (WSU)

Collaborator: Sara Serra (WSU)

Location: Monitor, WA Planting density: 5 ft x 12 ft (726 tree/A) Rootstock: OHF 87 Year of planting: 2012 Training system: biaxis

2 treatments: 1) Hand winter pruning (4 plots), 2) Mechanical+Hand winter pruning (4 plots) Mechanical pruning on March 23 2015 and April 18, 2016 Tractor speed: 1.8 m/h (10,000 rpm), Gillison’s hedger.

Gillison’s hedger in action (2015)

Weight of wood pruned by two pruning methods on Bartlett trees in 2015, trunk cross sectional area (TCSA cm2) 2015 and pruning time (h/A).

Mechanical+hand vs hand pruning of Bartlett/OHF 87 in 2015.

Mechanical

pruning time

6.9 sec/tree ≈

1.4 h/A

Mechanical+hand vs hand pruning:

Bartlett/OHF87 yield and fruit distribution 2015.

Treatment

Pruning

Mechanical+hand 18 B 6.3 B 162 0.33 B 0.92 B

Hand only 25 A 8.8 A 163 0.46 A 1.29 A

Significance

Significance: * p<0.05, ** p<0.01, *** p<0.001. SNK as post-hoc test for means discrimination.

Bartlett yield in Monitor, WA, August 2015

* * NS ** **

Number fruit /treeNet yield (lb /tree)

Avr. fruit weight (g)

Yield efficiency (lb /TCSA cm2)

Crop load (num. fruit /TCSA

cm2)

Pruning 2015 Yield (USton/Acre) Pear bin/Acre

Mechanical+hand 2.3 4.3

Hand only 3.2 6.1 (1 pear bin = 1050 lb)

Mechanical+hand vs hand pruning:

Bartlett/OHF87 fruit quality at T0 (+1month after harvest 2015).

Harvest 2015 Avr. fruit weight (g) IAD at harvest Overcolor

(%) Firmness (kg/cm2)

SSC (Brix) L a b

Hand 181 1.96 b 7.72 1.03 b 15.71 69.47 a -5.21 a 51.27 a

Mech+Hand 177 1.99 a 9.77 2.45 a 16.20 67.14 b -7.36 b 49.88 b

Significance NS * NS ** NS *** ** **

Hand Pruned Hand+ mechanically Pruned

Weight of wood pruned by two pruning methods on Bartlett trees in 2016, trunk cross sectional area (TCSA cm2) 2016 and pruning time (h/A).

Mechanical+hand vs hand pruning of Bartlett/OHF 87 in 2016.

Mechanical+hand vs hand pruning:

Bartlett/OHF87 yield 2016 (harvest 5th August 2016)

Mechanical+hand vs hand pruning:

Bartlett/OHF87 yield and fruit distribution 2016.

Pruning (2016) Yield (USton/Acre) Pear bin/Acre

Mechanical+hand 6.9 13 Hand only 14.1 27 (1 pear bin = 1050 lb)

Mechanical+hand vs hand pruning:

Bartlett/OHF87 fruit quality at T0 (+1month after harvest 2016).

HARVEST 2016 weight (g) T0 day0

IAD at T0 day0

Color parameter: Hue

(T0 day7)

Color parameter: Chroma (T0 day7)

IAD drop in 7days @RT

weight (g) drop in 7days

@RT

% red overcolor

Firmness (kg/cm2) SSC (Brix) destructive

DM % pH titratable acidity (% malic acid)

Hand only (ctrl) 211 A 1.86 95.04 52.37 1.56 A 8.53 9.98 0.85 13.74 A 15.00 A 3.69 B 0.38 A

Mech+Hand 196 B 1.96 96.11 52.56 1.48 B 8.76 12.10 0.79 12.67 B 13.85 B 3.79 A 0.33 B

Significance trt ** NS NS NS ** NS NS NS *** * ** **

Significance class NS *** NS NS * NS NS NS *** NS NS *

Significance trt*class NS NS NS NS NS NS NS NS NS NS NS NS

Fruit distribution at harvest 2016 in IAD maturity classes Fruit distribution at harvest 2016 in IAD maturity classes

+ maturity -

Thank you! Acknowledgments: • Ryan Sheick, • Angela Knerl, • Alex Goke, • Brendon Antony

http://treefruit.wsu.edu/videos/pruning-bartlett-pears-to-optimize-fruit-quality/

Conclusions: • An aggressive mechanical pruning can impact the fruit size, and yield,

reducing significantly the tree structure and canopy. • If basal branches already present blind wood the mechanical cut will

probably reduce significantly the number of flower buds and so the production.

• Mechanical winter pruning combined with the “click” pruning can reduce the blind wood.

• Alternating mechanical pruning on the two sides can be a solution to minimized the yield reduction.

• Be careful in summer for potential fire blight risk!