Budburst and flowering intensity by the spraying of dormancy-breaking products in ‘Eva’ apple trees

Abstract

Spraying of dormancy-breaking chemicals is a mandatory procedure to produce temperate fruits in low-chill regions. Although hydrogen cyanamide (HC) + mineral oil (MO) show efficiency enhancing budburst, the usage of HC is restricted in some countries due to its toxicity. Therefore, this research aimed to evaluate the efficiency of spraying different dormancy-breaking agents on ‘Eva’ apple tree buds, under the conditions of the Depressão Central of Rio Grande do Sul, Brazil. Different doses of Erger® (0, 2, 3, 4, 5%) + 3% Ca(NO3)2 were tested and compared with MO (4%) or MO (4%) + HC (0.6%). Budburst rate of apical and axillary buds, physiological alterations in buds, return bloom, yield and fruit weight were evaluated. Erger® treatments efficiently enhanced budburst, with a result equivalent to HC + MO treatment. The budburst rate increased as the Erger® dose increased, also causing the increment of the return bloom in the following year. However, doses of 4 and 5% caused the death of shoots. The activity of the peroxidases and the content of H2O2 in the buds were affected by the treatments. Yield and fruit mass were different in response to treatments, although the effect varied between years. Erger® + Ca(NO3)2 spraying increase budburst in apical and axillary buds of ‘Eva’ apple tree in low-chill conditions and doses up to 3% of the commercial product do not cause toxicity.