A new mechanical thinner to reduce hand labor in peach

Crop load adjustment is often a necessary practice to yield fruit of marketable quality. In peach, manual thinning is still the most common method used worldwide to reduce excessive crop load. However, manual thinning is time-consuming, as it requires 100-300 h ha^‑1 labor, and expensive, as it accounts for up to 30% of total costs depending on the cultivar, the orchard system and the year. Previous studies showed that mechanical thinning can effectively reduce the time required for follow-up hand thinning with promising but variable results according to the device, the timing and the orchard characteristics. In this study, a thinning device recently developed in France was tested in Cesena, Italy, in a commercial orchard of the peach 'Royal Glory' trained to a palmette. This device consists in a tractor-mounted rotor equipped with elastic rods radially inserted on a central axe. Mechanical thinning was performed at blooming time, at 6 km h^‑1 speed. The length of the bearing shoots and the number of flowers per shoot before and after mechanical thinning were recorded, and the blossom removal percentage was calculated. Control plots (i.e., standard thinning practice consisting in only manual crop load reduction before pit-hardening onset) were also included to assess the potentialities of the machine for time saving. Percentage of flowers removed mechanically averaged 46%, with a trend of more thinning on the longer shoots. On the other hand, flower removal percentage was not affected by the insertion angle of the shoots with respect to the plane intercepted by the row. Based on this preliminary test, the new device can effectively thin flowers with minimal harm to the canopy, allowing a reduction in the follow-up fruit manual thinning as compared to the control.