Thinning in peach: Past, present and future of an indispensable practice

Peach (Prunus persica L. Batsch) trees need to be thinned in order to guarantee yield of fruits of marketable size and a sufficient return to bloom in the following season. In this fruit crop, however, thinning is often complicated by several endogenous as well as exogenous factors, such as genotype, orchard structure, environmental conditions and agronomic management, and the current thinning methods (manual, mechanical or chemical), taken singularly, present more disadvantages than advantages. Therefore, the only possible option is currently represented by the adoption of a “thinning strategy”, consisting in subsequent interventions at different phenological stages, to finely tune the final fruit load along its physiological evolution. Such strategies must also consider the ongoing climate changes, which further complicates the thinning interventions also due to the lack of Decision Support Systems (DSSs), and the current trends of the global market. The present review takes a picture of the current situation of peach thinning, with a particular focus on the current development of new chemical thinners, and its future perspectives. Some general remarks are made considering the evolution of the global market and the obstacles found in peach research in some of the most traditional peach areas of the world.