The Bestcur preparation is a biological product containing extracts of Citrus aurantium L. and Citrus reticulata in amounts from 30 to 50%, as well as free amino acids in an amount of 6.0% (including total nitrogen – 1.3%, complex organic acids – 8.5% and bioflavonoids). The preparation is intended for use in horticulture. Bestcur is applied to blackberry and raspberry crops, including those intended for retail sale to the public. The application of the preparation promotes increased crop yield due to the combined action of its components.