Do dormancy breakers have a role in fruit production?

Unlike many northern hemisphere pome fruit production regions, the climate across Australian apple growing regions is characterised by gradual transitions between seasons, and often lack of winter chill. This means that fruit trees come out of winter dormancy slowly and erratically with flowering periods lasting up to 6 weeks. Future predicted changes in climate also means that more fruit production areas will become marginal in terms of achieving sufficient chill exposure for specific cultivars. So what is the problem with non-synchronous bud-break and flowering? Extended bud-break and flowering can make cultural practices such as fruit thinning, tree training and harvest complicated due to the different stages of growth on the tree at any one time. The long flowering period often makes for unpredictable responses to thinning chemicals. This, combined with a lack of uniformity of fruit maturity at harvest necessitating multiple picks from each tree, impacts on orchard profitability. Bud break can be manipulated by the use of chemical rest breaking agents (dormancy breakers). In addition to bringing about a synchronous bud-break, these chemicals can also be used to manipulate flowering (both time and length). This update will briefly discuss past work and provide an introduction to work planned this coming season in project AP12029 (Understanding apple and pear production systems in a changing climate) in relation to assessment of dormancy breaking sprays as a potential orchard management adaptation to inadequate winter chill.