CHEMICAL THINNING OF
PEARS IN SOUTH AFRICA
Karen Theron
Chair in Pre-harvest Deciduous Fruit Research
Dept. Horticultural Science / HORTGRO Science
Faculty of AgriSciences
Stellenbosch University
INTRODUCTION
 Currently registered on pears
 New developments
INTERPERA, South Africa – Nov. 2016
INTRODUCTION: Cultivar distribution in South Africa
14%
Other
6%
Abate Fetel
34%
Packham's Triumph
20%
Williams Bon Chretien
Forelle
26%
Forelle
INTERPERA, South Africa – Nov. 2016
CURRENT REGISTRATIONS
 Currently registered on pears
- Packham’s Triumph
- Forelle
- Williams Bon Chretien
- Abate Fetel
 Packham’s Triumph - nothing
 Forelle - metamitron
 Williams Bon Chretien – 6-BA, metamitron
 Abate Fetel - metamitron
INTERPERA, South Africa – Nov. 2016
CURRENT REGISTRATIONS
 Metamitron on FOR, WBC, AF
- Nevis™ 150 SC at 1 200 ml ha-1
- single application
- ±10 mm fruitlet diameter
- 1000 – 1500 L water ha-1
INTERPERA, South Africa – Nov. 2016
CURRENT REGISTRATIONS
 6-BA (MaxCel®) on Williams Bon
Chretien only
- 8-12 mm fruitlet diameter
- 750 ml MaxCel® / 100 L water
- 18°C for 2-3 days afterwards
INTERPERA, South Africa – Nov. 2016
EARLIER EVALUATION
 NAD on Williams Bon Chretien
- 30 mg.L-1 GoldenThin (10%)
- 8 – 12 mm fruitlet diameter
- not used
INTERPERA, South Africa – Nov. 2016
FUTURE NEEDS
 Alternatives for Forelle
- First increase set, then thin
- Small fruited cultivar
- NAA + 6-BA, ACC and ABA
INTERPERA, South Africa – Nov. 2016
NEW DEVELOPMENTS: ‘Forelle’
 NAA plus 6-BA tank-mix
INTERPERA, South Africa – Nov. 2016
NEW DEVELOPMENTS: ‘Forelle’ NAA & 6-BA
Dose
(Rate per 100 L)
Application Timing
Untreated control
-
-
Bloom Bandit mech. thinning
-
8-10 mm
PoMaxa (NAA)
16 ml
8-10 mm
ACC
400 ml
8-10 mm
MaxCel (6-BA)
500 ml
8-10 mm
MaxCel (6-BA)
750 ml
8-10 mm
MaxCel + PoMaxa
500 ml + 16 ml
8-10 mm
MaxCel + PoMaxa
750 ml + 16 ml
8-10 mm
Treatment
INTERPERA, South Africa – Nov. 2016
NEW DEVELOPMENTS: ‘Forelle’ NAA & 6-BA
Fruit Set (%)
Number of fruitlets
removed
Untreated control
57.3 bac
251 a
Bloom Bandit mech. thinning
48.0 dc
199 bac
PoMaxa @ 16 ml / 100 L
59.3 ba
212 ba
8.1 f
26 d
MaxCel @ 500 ml / 100 L
67.3 a
201 bac
MaxCel @ 750 ml / 100 L
54.9 bc
208 ba
MaxCel @ 500 ml + PoMaxa @ 16 ml
41.9 ed
158 bc
MaxCel @ 750 ml + PoMaxa @16 ml
36.1 e
151 c
Treatment
ACC @ 400 ml / 100 L
Significance Level
<.0001
INTERPERA, South Africa – Nov. 2016
<.0001
NEW DEVELOPMENTS: ‘Forelle’ NAA & 6-BA
Treatment
Yield
(Kg/boom)
Yield
(Ton / ha)
Avg. Fruit
mass (g)
Untreated control
46.1 a
68.3
151.5 c
Bloom Bandit mech. thinning
36.8 b
54.5
169.5 b
PoMaxa @ 16 ml / 100 L
40.5 ba
59.9
160.6 cb
ACC @ 400 ml / L
18.6 c
27.6
202.6 a
MaxCel @ 500 ml / 100 L
36.3 b
53.8
162.5 cb
MaxCel @ 750 ml / 100 L
37.5 b
55.5
162.1 cb
MaxCel @ 500 ml + PoMaxa @ 16 ml
40.4 ba
59.8
158.2 cb
MaxCel @ 750 ml + PoMaxa @16 ml
36.5 b
54.0
165.1 b
Significance Level
<.0001
INTERPERA, South Africa – Nov. 2016
-
<.0001
NEW DEVELOPMENTS: ‘Forelle’ NAA & 6-BA
Return Bloom
(%)
Treatment
Untreated control
25.1 c
Bloom Bandit mech. thinning
21.3 c
PoMaxa @ 16 ml / 100 L
23.1 c
ACC @ 400 ml / 100 l
47.0 a
MaxCel @ 500 ml / 100 L
36.5 b
MaxCel @ 750 ml / 100 L
25.5 c
MaxCel @ 500 ml /100 L + PoMaxa @ 16 ml / 100 L
45.0 ab
MaxCel @ 750 ml /100 L + PoMaxa @16 ml / 100 L
36.1 b
Significance Level
<.0001
INTERPERA, South Africa – Nov. 2016
NEW DEVELOPMENTS: ‘Forelle’
 ACC (aminocyclopropanecarboxylate oxidase) and
ABA (abscisic acid)
S-adenosyl-L-methionine (SAM) converted to ACC by ACC
synthase
ACC oxidized by ACC oxidase to ETH
INTERPERA, South Africa – Nov. 2016
NEW DEVELOPMENTS: ‘Forelle’ ABA & ACC
Treatments
Untreated control
ABA @ 50 g / 100 ℓ water at 8-10 mm fruit Ø
ABA @ 100 g / 100 ℓ water at 8-10 mm fruit Ø
ABA @ 150 g / 100 ℓ water at 8-10 mm fruit Ø
ACC @ 75 ml / 100 ℓ water at 8-10 mm fruit Ø
ACC @ 150 ml / 100 ℓ water at 8-10 mm fruit Ø
ACC @ 225 ml / 100 ℓ water at 8-10 mm fruit Ø
ACC @ 300 ml / 100 ℓ water at 8-10 mm fruit Ø
INTERPERA, South Africa – Nov. 2016
NEW DEVELOPMENTS: ‘Forelle’ ABA & ACC
Average fruit set
per cluster
Average number of
fruitlets removed by hand
thinning per tree
Untreated control
1.18 ab
225 a
ABA @ 50 g at 8-10 mm
1.20 a
205 a
ABA @ 100 g at 8-10 mm
0.83 c
181 ab
ABA @ 150 g at 8-10 mm
0.89 bc
138 b
ACC @ 75 ml at 8-10 mm
1.23 a
221 a
ACC @ 150 ml at 8-10 mm
1.25 a
199 a
ACC @ 225 ml at 8-10 mm
1.09 abc
187 ab
ACC @ 300 ml at 8-10 mm
1.07 abc
210 a
0.0372
0.0187
Treatment
(Lushof, Warm Bokkeveld)
Significance level
INTERPERA, South Africa – Nov. 2016
NEW DEVELOPMENTS: ‘Forelle’ ABA & ACC
Treatment
(Lushof, Warm Bokkeveld)
Yield efficiency in kg
Estimated yield per
per cm trunk
hectare (ton)
circumference
Untreated control
0.52 ns
45.6
ABA @ 50 g at 8-10 mm
0.55
46.5
ABA @ 100 g at 8-10 mm
0.52
45.4
ABA @ 150 g at 8-10 mm
0.50
44.5
ACC @ 75 ml at 8-10 mm
0.48
41.8
ACC @ 150 ml at 8-10 mm
0.54
44.7
ACC @ 225 ml at 8-10 mm
0.50
42.5
ACC @ 300 ml at 8-10 mm
0.44
39.3
Significance level
0.5075
INTERPERA, South Africa – Nov. 2016
-
NEW DEVELOPMENTS: ‘Forelle’ ABA & ACC
Treatment
(Lushof, Warm Bokkeveld)
Average fruit weight
(g)
Average fruit diameter
(mm)
Untreated control
146.1 b
62.5 bc
ABA @ 50 g at 8-10 mm
158.1 ab
63.8 ab
ABA @ 100 g at 8-10 mm
166.5 a
65.6 a
ABA @ 150 g at 8-10 mm
166.7 a
65.1 a
ACC @ 75 ml at 8-10 mm
144.6 b
60.8 c
ACC @ 150 ml at 8-10 mm
147.9 b
60.9 c
ACC @ 225 ml at 8-10 mm
144.3 b
60.6 c
ACC @ 300 ml at 8-10 mm
153.8 ab
Significance level
0.0105
INTERPERA, South Africa – Nov. 2016
61.9
bc
<.0001
NEW DEVELOPMENTS: ‘Forelle’ ABA & ACC
Treatment
(Oak Valley, Elgin)
Average fruit set
per cluster
Average number of fruitlets
removed by hand thinning
per tree
Untreated control
1.38 ab
273 b
ABA @ 50 g at 8-10 mm
1.63 a
243 bc
ABA @ 100 g at 8-10 mm
1.37 ab
181 de
ABA @ 150 g at 8-10 mm
1.21 bc
174 de
ACC @ 75 ml at 8-10 mm
1.46 ab
323 a
ACC @ 150 ml at 8-10 mm
1.30 bc
220 cd
ACC @ 225 ml at 8-10 mm
1.02 cd
155 ef
ACC @ 300 ml at 8-10 mm
0.73 d
123 f
Significance level
<.0001
<.0001
NEW DEVELOPMENTS: ‘Forelle’ ABA & ACC
Treatment
(Oak Valley, Elgin)
Yield efficiency in kg
per cm trunk
circumference
Estimated yield
per hectare *
(ton)
Untreated control
1.00 ns
68.9
ABA @ 50 g at 8-10 mm
0.97
70.0
ABA @ 100 g at 8-10 mm
0.99
69.8
ABA @ 150 g at 8-10 mm
0.99
71.2
ACC @ 75 ml at 8-10 mm
1.06
79.2
ACC @ 150 ml at 8-10 mm
0.94
66.2
ACC @ 225 ml at 8-10 mm
0.90
61.8
ACC @ 300 ml at 8-10 mm
0.88
64.4
Significance level
0.2085
-
NEW DEVELOPMENTS: ‘Forelle’ ABA & ACC
Treatment
(Oak Valley, Elgin)
Average fruit weight
(g)
Average fruit diameter
(mm)
Untreated control
119.9 c
58.1 c
ABA @ 50 g at 8-10 mm
126.5 bc
58.7 c
ABA @ 100 g at 8-10 mm
130.6 bc
59.5 bc
ABA @ 150 g at 8-10 mm
149.6 a
62.3 a
ACC @ 75 ml at 8-10 mm
129.2 bc
59.4 bc
ACC @ 150 ml at 8-10 mm
129.2 bc
59.5 bc
ACC @ 225 ml at 8-10 mm
136.4 ab
60.8 ab
ACC @ 300 ml at 8-10 mm
147.5 a
62.4 a
Significance level
0.0005
INTERPERA, South Africa – Nov. 2016
0.0002
NEW DEVELOPMENTS: ‘Forelle’ NAA + 6-BA
 MaxCel + PoMaxa reduced fruit set significantly vs MaxCel
alone
 Mechanical thinning and MaxCel @ 750 ml + PoMaxa @ 16
ml, improved fruit size significantly vs. untreated.
 MaxCel & MaxCel + PoMaxa improved return bloom
INTERPERA, South Africa – Nov. 2016
NEW DEVELOPMENTS: ‘Forelle’ACC
 ACC thinned ‘Forelle’ pears significantly in 1 of 2 studies
 ACC increased fruit size significantly at 225 – 300 ml / 100 L
INTERPERA, South Africa – Nov. 2016
NEW DEVELOPMENTS: ‘Forelle’ABA
 ABA thinned ‘Forelle’ pears significantly in 2 of 2 studies
 ABA increased fruit size significantly at 100 – 150 g / 100 L
 ABA showed some slight phytotoxicity on the leaves
INTERPERA, South Africa – Nov. 2016
ACKNOWLEDGEMENTS
 Schalk Reynolds, Philagro SA
 Gustav Lötze, SU
 Lushof & Oak Valley Estates
INTERPERA, South Africa – Nov. 2016