Influence of budburst inducers replacing hydrogen cyanamide on phenological parameters of ‘Castel Gala’ apple trees

Abstract

Hydrogen cyanamide is the main budburst inducer applied in Brazil, even though it is highly toxic to the environment. This fact has triggered the search for alternatives with similar efficiency and lower toxicity. This study aimed at evaluating the efficiency of different budburst inducers by using phenology on the field and by applying the biological method of single bud. The experiment was conducted in an experimental orchard of ‘Castel Gala’ apple trees in both 2019/2020 and 2020/2021 seasons. Seven treatments, divided into three concentrations of Erger® associated with calcium nitrate, three concentrations of garlic extract associated with mineral oil and control (no application), were applied in the first season. The second season consisted of the seven treatments applied in the first season and two treatments of hydrogen cyanamide, at different concentrations, associated with mineral oil. Evaluation was carried out on the field by checking budburst and flowering percentages, fruit set and dates of phenological stages. In the second season, the test of the single bud evaluated percentages of total budburst and mixed buds, average budburst time (ABT) and average time for leaf opening (ATLO). The results show that garlic extract is not efficient inducing budburst in 'Castel Gala' apple trees; while the budburst inducers hydrogen cyanamide 1% + mineral oil 3% and Erger® 7% + calcium nitrate 5% are the best alternative for inducers, being the last main alternative to hydrogen cyanamide in 'Castel Gala' apple trees budburst induction. The biological method of single bud did not show to be a good alternative to evaluate the efficiency of budburst inducers in 'Castel Gala' apple trees. .