Sequential applications of budbreak promoters in hail-netted apple trees in southern Brazil: a canopy stratification approach

This work sought to evaluate sequential applications of budbreak promoters on hail-netted apple trees in southern Brazil, focusing on the effects at different canopy levels. One or two sprays were applied to ‘Baigent’ and ‘FujiKiku 8’ trees under black net in a commercial orchard in Vacaria/RS. Hydrogen cyanamide (0.34%) with mineral oil (3.5%) was the unique/first application. Mineral oil(3.5%) alone or with hydrogen cyanamide (0.17%, 0.34%), Erger® (1.5%), and Syncron® (1.5%) constituted the reapplications. During the 2017/18 and 2018/19 seasons, phenology, budbreak, fructification, and fruit production were assessed in the lower and upper halves of the canopy of treated and non-treated trees. The budbreak promoters anticipated blooming, generally increased and reduced budbreak and fructification, respectively, without changing production. The upper canopy exhibited delayed budburst/blooming compared to the lower one but showed higher fruiting and advanced harvest in ‘Baigent’. One and two sprays produced similar results and few were the differences among the sequential treatments. Little influences may be attributed to adverse weather conditions, such as water scarcity and low thermal accumulation. The second application is commonly used in the region’s apple orchards, as better outcomes than with just one have been reported. In this context, additional research is required to validate the schemes adopted for hail-netted ‘Baigent’ and ‘Fuji Kiku 8’ trees cultivated in southern Brazil.