Without thinning of peach flowers or fruits we cannot achieve the desired quantity and quality of the yield. There are three known methods of thinning: mechanical, chemical and hand thinning. Most often peaches are hand thinned, whereas chemical and mechanical thinning serves as an alternative primarily in intensive orchards. With mechanical thinning, where physical removal of blossoms is concerned, the effect is visible immediately, and with the inspection of the orchard it is determined whether the thinning is to be reduced or increased. A disadvantage is non-selectivity and unevenness of thinning in the crown. In Canada, a method has been tested where blossoms are removed under high pressured water without any chemicals, but it is still in the process of optimization. Over the past years, many chemical thinning agents have been tested, such as: abscisic acid, tergitol, gibberellic acid, hydrogen cyanamide, ammonium thiosulfate, armothin, lime sulfur, eugenol. Chemical thinning reduces the cost of thinning, allows a relatively quick application over a short period of time, phytotoxicity can occur, is non-selective and in most cases requires additional corrective hand thinning. For a successful chemical thinning it is important to know the concentration of the thinner, and the success also depends on weather conditions and peach cultivars. Despite all the alternatives with which fruit growers try to reach the equivalent results to hand thinning, hand thinning is still the best. The problem of hand thinning is the need for a large number of skilled labour, time and money, and the advantage is selectivity, which contributes to a bigger and better quality yield.
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