Chemical thinning of 'Fuji' apples growing in a mild winter climate

Apple trees growing in mild winter conditions, such as in Southern Brazil, bear fruit mainly in brindles and in axillary buds, setting 4 or more fruits per cluster, with short peduncles that increase hand thinning labor. The thinning effects of NAA (10 and 15 mgL(-1)),, Carbaryl (750 mgL(-1)), Benzyladenine (75 and 340 mgL(-1)), and Ethephon (100 mgL(-1)), on 'Fuji, apples, were evaluated from 2001 to 2004. Experiments were carried out in Cacador and Fraiburgo (27 degrees S), in Santa Catarina State, Brazil, in orchards trained to a central leader system. The chemicals were applied singly or as combinations of two products, at blooming and after blooming stages, with fruits up to 24 mm in diameter. Benzyladenine applied alone or in combination with NAA reduced the fruit set of 'Gala' if compared to the NAA + Carbaryl the standard treatment (control). NAA 10 mgL(-1) at 5 DAFB + Benzyladenine 75 mgL-1 increased mean fruit weight by 10.4% in relation to the hand thinning treatment. In 'Fuji' trees, NAA + Benzyladenine reduced the number of clusters with 3 or more fruits. Benzyladenine was efficient when applied to fruits 10 mm in diameter. It also increased mean fruit weight and the percentage of fruits in the larger size classes. Benzyladenine at 160 mgL(-1) induced growth of axillary buds in the current season's terminals. Benzyladenine is a new and efficient alternative for thinning apples grown under mild winter climate.