Concentrations and time of applications of naphthaleneacetic acid on yield and quality of apples

Abstract

A field trial was carried out to evaluate the effects of concentration and time of application of naphthaleneacetic acid (NAA) on fruit thinning, quality and yield of apple (Malus domestica Borkh.) cv. Fuji, grafted on MM-106. Treatments consisted of hand thinning and application of 0, 7.5, 15, 22.5 and 30 ppm of NAA at 15, 20, 25 and 30 days after full bloom. Treatments were evaluated during 1981/82, in a six-year old commercial orchard, in São Joaquim 28°17’39” S, 49°55'56' O 1,388 m altitude), State of Santa Catarina, Brazil. NAA applied at 22.5 and 30 ppm resulted in the highest retention of fruits, which were of small size. At lower concentrations (7.5 and 15 ppm), NAA showed the best results in terms of thinning, size and average weight of fruits, when applied 15 or 20 days after full bloom. The best time for hand thinning was 25 - 30 days after full bloom. This work confirmed the usefulness of NAA as a chemical thinning agent. However, for best fruit size and distribution of fruits on the apple tree, additional hand thinning is recommended.