FRUIT THINNING EFFECTS IN THE APPLE CV. ´ROYAL GALA´

A trial was conducted for studying different thinning programs in apple cv. ‘Royal Gala’. The following treatments were applied in a completely randomized design: -1: NAA 10 mgL^-1 at 5mm fruit diameter (FD) + 6Benzyladenine (6BA) 50 mgL^-1 at 8 mm FD; -2: NAA 10 mgL^-1 at 5mm FD + 6BA 150 mgL^-1 at 8mm FD; -3: Carbaryl 1020 mgL^-1 at 5mm FD; -4: 6BA 100 mgL^-1 at 8mm FD; -5: 6BA 50 mgL^-1 at 5mm FD + 6BA 50 mgL^-1 at 8mm FD; and -6: Untreated control. The variables measured were: fruits/cm2 branch cross sectional area (BCSA), fruits/100 flower clusters, fruit set distribution, hand thinned fruits/cm² BCSA, hand thinned fruits/m, fruit weight, length (L), diameter (D), L/D relationship and firmness; and fruit commercial size classification. Treatments 1, 2, 3 and 4 significantly reduced the number of fruits/cm² BCSA in comparison with the control. The numbers of fruits/100 flower clusters was also significantly different from the control in treatments 1, 2, and 4. Treatment 5 did not differ from the control in both variables. Treatments 1, 2, and 4 had a higher amount of spurs without fruits than treatment 3, 5 and 6. After chemical applications, hand thinned fruits/cm² BCSA and hand thinned fruits/m were fewer in treatments 1, 2, 3 and 4. Fruits treated with BA had higher weights and diameters compared with the control. Fruit L/D relationship and firmness did not differ among treatments. BA treatments produced the larger fruit commercial sizes. The different combinations of NAA + 6BA and 6BA at 100 mgL^-1 were effective as thinners. Repeated applications of BA at 50 mgL^-1 did not have a good thinning effect but they increased fruit weight, diameter and length.