Fruit Growth, Development, and Thinning

1
Fruit Growth, Development, and Thinning

• Crop Management by Fruit Thinning

2
Fruit ThinningSet Required for Commercial Crop

• Large fruited crops
• 2 to 25
• Apple 2-8
• Pear 3-11
• Peach 15-20
• Asian Plum 3-10
• Apricot 20-25

• Small fruited crops
• 40-100
• Almond 20-100
• Blackberry 90-100
• Blueberry 40-95
• Cherry 20-75
• Cranberry 44-77
• Grape 30-70
• Kiwi 95-100

3
Fruit ThinningDisadvantage Reduce Fruit Yield
4
Fruit ThinningAdvantage Increase Fruit Size
5
Fruit Thinning

• Disadvantage
• Reduce fruit yield
• Advantages
• Increase fruit size

• Other Advantages
• Stimulate floral initiation
• Avoid alternate bearing
• Increase leaf to fruit ratio
• Increase fruit color/quality
• Reduce limb breakage
• Improve plant health

6
Fruit ThinningIncrease Economic Yield

• Small fruit
• Lower selling price
• Less demand
• More expensive to harvest
• 267 fruit per bushel for 2 fruit
• 132 fruit per bushel for 2.5 fruit
• Large fruit
• Better return with lower harvesting cost

7
Thinning RequirementsGeneral

• Small fruited crops are usually not thinned
• The earlier the thinning the greater the effect

8
Thinning RequirementsGeneral

• Small fruited crops are usually not thinned
• The earlier the thinning the greater the effect

9
Thinning RequirementsStone Fruits

• Peach
• Done up to 6 weeks after bloom
• In Texas, after chance of frost
• Remove gt50 fruit
• Leave 4 to 8 between fruit
• Done by hand
• Chemical thinning?

• Plum
• May alternate bear
• Leave 3 to 4 between fruit
• Done by hand

10
Thinning RequirementsPome Fruits

• Apples and Pears
• Yearly to avoid alternate bearing
• Maximum load fruit/spur
• Pears benefit less than apples
• Pears _at_ 60 dab
• Apples _at_ 40 dab

11
Thinning Methods

• Hand (clubs, brushes)
• Predetermined spacing
• Remove weak, damaged or small fruit
• Mechanical
• High pressure water at bloom
• Rope curtain
• Tree shaker
• Chemical

12
Thinning MethodsChemical

• Advantages
• Cost
• Labor
• Fruit size etc.
• Disadvantages
• Over thinning
• Foliage damage
• Variable results

• Thinning agents
• Caustic compounds
• Synthetic auxins
• Ethylene induction

13
Chemical Thinning Agents Caustic compounds

• DNOC (sodium 4,6 dinitro-ortho-cresylate)
• Prevents pollination
• Apply after king bloom has set
• Consistent with heavy setters
• May damage foliage

14
Chemical Thinning AgentsSynthetic auxins

• Carbaryl (sevin) (1-naphthyl N-methyl carbamate)
• Toxic to bees
• NAA (naphthalene acetic acid)
• NAD (naphthalene acetamide) - Safer than NAA
• Mode of Action
• Reduce phloem transport
• Upset hormone balance
• Induce ethylene production?
• Post bloom thinners
• Timing less exacting than with DNOC

15
Chemical Thinning AgentsEthylene Inducers

• Ethephon
• Not as reliable as others

16
Chemical Thinning AgentsReasons for Variable
Results

• Tree genotype
• Weather
• Tree condition

17
Reasons for Variable Results Tree Genotype

• Spur types are harder to thin than non spur
• Golden Delicious is harder to thin than Delicious

18
Post Bloom Thinning Sprays for Apples in
Washington and (New York)
grams/100 L water
19
Reasons for Variable Results Weather

• Increase absorption
• Rain
• High humidity
• Slow drying conditions
• Damage blooms
• Frosty nights
• High maximum temperature

20
Reasons for Variable Results Tree condition

• Young vs mature trees
• Very low vs. moderate vigor
• Light vs. heavily pruned
• Close vs. wide spaced trees
• Previous heavy vs. light crop

21
Any Questions?