Apple sprouting inducers for mild winter regions

In Brazil, the apple producing region is located at 26°46’31 latitude and at an altitude of 600 to 1,400 m where the chill for the ‘Gala’ and ‘Fuji’ cultivars is marginal. Under these conditions, it is necessary to use sprouting inducers to standardize sprouting and flowering and increase sprouting of both axillary buds and long shoots buds. For many years, hydrogen cyanamide has been used in combination with mineral oil, but its registration has been avoided for its toxicity, limiting therefore the cultivation of apple trees in these regions. Several products have been formulated with the aim of inducing sprouting in conditions where the chill is not enough to induce the release of dormancy. The objective was to test the technical and economic efficiency of the new products in the induction of apple tree sprouting from medium to high chilling demand. The experiments were carried out testing on ‘Gala’ and ‘Fuji’ new formulations, such as Erger, Syncron, Sibério, Florvit, TDZ, 2-(thiothiomethylthio) benzothiazole and mineral oil compared to hydrogen cyanamide in terms of concentrations and application times, as well as their reapplication. The products Erger, Syncron, Siberio, Florvit and TDZ proved to be efficient in inducing apple tree sprouting with results similar to hydrogen cyanamide and potential for commercial use. The reapplication of sprouting inducers improved the flowering uniformity and increased the sprouting percentage of apple trees, mainly in the upper part of the scion.