Alternatives to use of hydrogen cyanamide in bud breaking in apple 'Maxi Gala'

The main practice adopted for budburst induction in apples is to spray hydrogen cyanamide with mineral oil, though due to the toxicity of this molecule it is essential to find efficient alternative methods for breaking dormancy when chilling requirements are not achieved. This study was aimed at evaluation of alternatives to hydrogen cyanamide for breaking dormancy in the apple ‘Maxi Gala’. The trial consisted of a randomized block design with four replications in a commercial orchard located at the city Vacaria - RS during two crop years. The treatments were: T1 – control (no treatment); T2 – MO (mineral oil) 2%; T3 – VO (vegetable oil) 2%; T4 – VO 4%; T5 – MO 2% + VO 2%; T6 – MO 2% + 4% VO; T7 – 0.8% Dormex^® (hydrogen cyanamide 52% a.i.) + MO; and T8 – 4% Erger^® (biostimulant) + 4% Ca nitrate (CaN). The variables analyzed were budbreak, yield components, and fruit quality. The results were subjected to ANOVA and means comparison by Duncan’s test. The highest budbreak was observed in treatment T8; however, this also had the lowest production in the first year. The highest yield was observed in treatments T1, T4 and T6. The treatment with Erger^® despite having the highest budbreak was not positively reflected in its fruit yield. In the next cycle there were no significant differences for the variables average fruit weight, number of fruit, soluble solids and firmness. Treatments with Erger^®, MO 2% + VO 4%, and VO 4% alone had the highest yields. For the growth cycles in 2012/13 and 2013/14, all treatments advanced and standardized the budbreak compared to control. The treatment of MO 2% + VO 4% promoted budbreak of apple trees with the same efficiency as the use of hydrogen cyanamide.