Fruitlet thinning in 'Conference' pears by use of BAUM device

Experiments were carried out for two years 2009 and 2011 on 10-year-old pear orchard realized with the cultivar 'Conference' on rootstock Cydonia S1. The following treatments were evaluated: two treatments with mechanical thinning using BAUM device operating at the same tractor speed but at different rotors speed. The mechanical thinning abscission was integrated after bloom with commercial BA formulates (Paturyl or MaxCel) or with NAA (Pomonit Super 050 SL) or by hand thinning performed after June drop. Data collected with mechanical thinning were compared with those obtained with hand thinning, Paturyl 100 SL and Pomonit Super 050 SL. The following results were obtained: in 2009, cold weather during flowering caused very slow growth of fruitlets and reduced their tendency to fall. Then, the best thinning results were found after mechanical thinning with the BAUM device with low tractor and low rotors speed, and with complementary hand thinning. The best abscission efficacy was obtained with the mechanical thinning, where a complementary chemical thinning was done with Pomonit Super 050 SL after blooming. Paturyl 100 SL application instead did not modify significantly the abscission value reached with mechanical thinning. In 2011 very heavy fruit set in control trees was noticed. Mechanical thinning alone reduced fruit set by 12-27% and a further reduction was obtained with complementary hand or chemical thinning with BA (MaxCel) only. In 2011, BA used on trees earlier mechanically thinned, induced a further 35% fruit set reduction. In both trial years (2009 and 2011), the best mean fruit weight was induced by mechanical and complementary hand thinning after June drop. Neither symptoms of phytotoxicity nor mechanical injury were observed. In addition mechanical thinning did not affect return blooming of 'Conference' pear trees in both experiments. The different results achieved in the trial years with the chemical thinning, in particular with BA, are probably related to climatic conditions.