Report on apple fruit thinning trials carried out at the Bologna University in 2004

Four experiments were performed on “Gala” and “Fuji” apples in orchards located at the Experimental Farm of the Bologna University and in the Ferrara district area. In the experiment (I) BA from two different commercial sources was applied at 50, 75, 100, 150ppm; in the experiment (II) BA was tested at 100ppm in combination with 0.15% of polyethoxylated sorbitan or with a 0.3% mixture of aminoacids; in the experiment (III) BA was tested at 150ppm and at 300ppm alone or in combination with 30ppm NAA; in the experiment (IV), BA was applied at 150ppm alone or at 100ppm in combination with 10ppm NAA or 237ppm Carbaryl, and it was compared with Carbaryl oil alone (1.5 kg/ha). Each treatment was applied when king fruit reached 10 mm diameter. In the experiment I the two different BA induced a fruit abscission higher than in control tress. A tendency to increase average weight in treated fruits was observed and a dose related effect was found specially with the BA from the second source. When BA was applied in combination with the two wetting agents (experiment II) the effect on abscission and fruit weight was increased. On cv Gala (experiment III), all the applications caused a fruit abscission higher than control, and the highest effect was obtained in the presence of NAA. Similar results were recorded also for average fruit weight. In the trial performed in the Ferrara district area (experiment IV), all the applications caused a decrease in yield and crop load at harvest, but not in average fruit weight. A general effect on fruit quality traits (increase in flesh fimness and soluble solid content) was observed in all the experiments after applications of BA alone or in combination with other substances