Correlation between thinning amount and fruit quality in peach and nectarine.

Peach and nectarine trees usually set more fruit than necessary for a quality crop. Thinning is an important means to improve size and quality and to stimulate floral initiation for the following year’s crop. Thinning done at the wrong time, or poor thinning, can cause extreme variability in size and quality. To optimize the period and the amount of thinning, a two-year trial was carried out on Elegant Lady peach trees and Venus nectarines, evaluating the influence of light, medium and heavy manual thinning on size, weight and organoleptic traits of fruits. June drop in unthinned trees caused an irregular distribution of fruit remaining on trees, leading to an excessive yield of small sized, poor quality fruits. Intense thinning substantially reduced yield, but fruits were “extra size” and not suitable for marketing, and a high percentage of them were deformed. The best results in terms of quality and size were obtained with medium thinning.