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Thinning and Return Bloom

Chapter authors - Teryl Roper, Brent Black

 

While the precise mode of action of PGR thinning agents is not clearly understood, evidence is accumulating that the carbohydrate status of the tree plays a key role in plant sensitivity.  Carbohydrate status is affected by light levels (more light = more photosynthesis = improved carbohydrate levels) and by overall tree health. 

This effect occurs both at the whole-tree and the individual-branch level.  Overcast conditions and internal shading both make the fruit more sensitive to PGR thinning applications.  Likewise, well-exposed branches under full sunlight conditions tend to be more difficult to thin.

Additional Information

Thinning Apple Fruit

Thinning Stone Fruit

Controlling Apple Tree Vigor

Improving Fruit Quality

Managing Fruit Maturity