Effect of growth regulators on ovary thinning to increase yield and quality of apple fruits

The aim of the research is to study the effect of growth regulators based on alpha-naphthylacetic acid (Diramid) and 6-benzyladenine (Decimator) on ovary thinning to increase the yield and quality of apple fruits. The paper presents the results of a study of the effect of foliar treatments with growth regulators on ovary thinning in apple trees grown in the southern part of Russia. These preparations belong to a group of growth regulators aimed at reducing the number of developing fruits. The main active ingredients of Diramid are alpha-naphthylacetic acid and of Decimator are 6-benzyladenine, with the addition of chemical components that ensure long-term preservation of the preparation and good adhesion of the suspension during treatment (Application № 2024113093 (029464) dated 15.05.2024 "Composition for chemical thin-ning of fruit tree ovaries and increasing branching of seedlings"). The treatments with preparations were carried out on the Gold Rush apple variety with an apple diameter of 8–12 mm, which made it possible to leave 1–2 central, larger fruits out of 3–4 set fruits. The use of growth regulators allowed to improve the commercial quality of fruits, which was reflected accordingly in the amount of the obtained yield, which in the experimental variants was 1.2–2.4 t/ha more than in the control, due to the greater weight of apples. The yield of premium and first grade fruits averaged 85 %. The quality indicators of apples (weight, dry matter content, sugars) were 11–18 % higher when using Diramid and Decimator preparations.