Apple rest breaking linked to dormancy model

The objective of the study was to evaluate safer, more effective rest-breaking agents (RBA) for apples. Between 2008/9 and 2011/12, the same trees in an orchard of Royal Gala (RG) and an orchard of Granny Smith (GS), on one farm in Elgin, were treated with various commercial and potential RBA between five and six times during August, September and October. Control trees were left untreated. A motorised rack-sack mist blower was used and treatments applied to run-off unless specified. Bud break (BB), flowers/shoot and fruit/shoot on pre-marked one-year-old shoots were recorded. Number and mass of fruit/tree were recorded at commercial harvest time/s.  One carton of fruit/tree was used for recording fruit quality. Results depended on the year, RBA and application date. Most RBA improved BB with an optimum application date. Most RBA and application dates had no effect on total yield. Earlier RBA applications tended to improve fruit size. Application date tends to be more important than the RBA, but cannot be predicted. It is recommended that further studies to predict the optimum application date are necessary.