Bloom Mechanical Thinning Improves Fruit Quality and Reduces Production Costs in Peach

摘要

Crop load regulation is essential to achieve high fruit quality. In peach no reliable chemical thinners are available and hand thinning is the standard method used although it requires a high number of persons in a short span of time and is very expensive. To search for an alternative to hand-thinning operation, in 2009 bloom mechanical thinning trials were set up on peach testing a German mechanical device originally designed to thin apple flowers. First trials in Italy, they were made possible by the wide presence in Piedmont, North-West Italy of peach orchards trained to narrow canopy systems, which allow optimal string penetration through the canopy. The efficiency of string thinner Darwin 300 was assessed in peach and nectarine orchards trainedto perpendicular Y or central leader. Trees were mechanically thinned at 150-180 rpm rotor speed and 6-7 km/h vehicle speed; hand thinned trees served as control. Since spring frosts occur in the study area, mechanical thinning was performed at full bloom and until phase 72, BBCH scale. Mechanical thinning reduced labor costs as compared with hand-thinning control and increased crop value due to larger fruit size. Mechanical blossom/fruitlet removal ranged from 14% to 70%, according to rotor and vehicle speeds and labor requirement for follow-up hand thinning was reduced by 29% to 75%. Distribution of fruits in high value sizes increased, determining a positive economic impact. No damages were detected on fruit, pointing out that mechanical thinning could represent an interesting alternative to hand thinning also in peach production regions characterized by spring frosts.