Publication 360, Guide to Fruit Production: Chemical Thinning of Apples

Excerpt from Ch. 4, Publication 360, Guide to Fruit Production 2012-2013,

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  1. Other Information on Apples
  2. Chapter 4: Apple Calendar - PDF 357 kb
  3. Related Links

Chemical Thinning of Apples

Thinning of apples will:

  • improve average fruit size and finish
  • create more uniformity in the crop
  • encourage return bloom and annual bearing

The objective of thinning is to reduce clusters to single fruitlets on most cultivars, preferably the king bloom fruitlet, and to adequately space fruit to every other bearing spur. An additional benefit of thinning is reduced probability of pest damage. Some pests are more likely to damage clustered fruit.

Early thinning is important. Thinning near bloom or shortly afterward will increase average fruit size and maximize return bloom the next year.

Grower experience is the best guide to thinning needs, so it is important to document the previous thinning history including rates, conditions at time of application, and results. Other factors include:

  • the cultivars involved
  • fruit sizes required
  • strength of bloom
  • bee activity
  • weather conditions during pollination and following fruit set

Compared to a tree with an excessive crop load, a well-thinned crop has better colour and is more efficient to harvest, which reduces labour costs per bin.

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Author: OMAFRA Staff
Creation Date: 25 June 2007
Last Reviewed: 14 May 2012