The use of dormancy-breaking sprays could help apple and pear growers adapt to warmer years because dormancy breakers can stimulate earlier, more homogenous bud burst and flowering in a number of crops grown in mild climates worldwide.
Fruit set, yield & maturity at harvest (continued from last month)
Fruit set was not significantly different between treatments at any location indicating the compaction of the flowering period did not negatively, or positively, impact the effectiveness of pollination.
In Queensland, fruit maturity was advanced in trees treated with Dormex, Erger and Waiken compared with untreated trees, reflecting the difference in flowering dates.
There was no measurable reduction in the variability of fruit maturity at harvest with any of the sprays (assessed by looking at colour and Starch Pattern Index), despite the significant effect on compaction of flowering.
In Western Australia, fruit maturity was slightly advanced in the Dormex treated trees, although it was not statistically significant. Grower observation indicated that the colour was more intense in the Dormex treated trees.
There were no differences in harvest timing or variability of maturity at harvest between treatments in Tasmania.
Total yields were not affected by any of the dormancy-breaking sprays at any location.
Conclusion
The dormancy-breaking sprays tested (Waiken, Dormex and Erger) were able to advance flowering time and reduce the flowering period in Gala, with differences observed between sites.
The ability of these sprays to produce a more compact and uniform flowering period has a number of benefits including improved management of bee hives, flowering pests and chemical thinning practices.
Improvements in fruit set and harvest quality have been reported elsewhere but were not observed here.
The impacts on green tip and flowering will vary with the timing of spray application and are likely to vary between region and seasons, depending on the level of accumulated chill. It is important to consider the flowering time of polliniser varieties to ensure flowering overlaps so that fruit set is not affected.
Harvest timing
Advances in harvest timing were observed with the dormancy-breakers and generally reflected differences in flowering dates.
The ability to manipulate harvest timing can be useful in some situations where advantage can be taken of a high-price market window.
Fruit quality
Possible effects on fruit quality and variability of maturity at harvest remain unclear and more work is required to test the potential of these products to reduce the harvest window.
Viable adaptation tool
It is likely that these products are a viable adaptation tool for some varieties in lower chill years. But, in planning for production in future warmer climates, how low can winter chill drop before the use of these dormancy-breaking sprays is no longer profitable? This question remains to be answered.
Dr Heidi Parkes, horticulturist, DAF; Susie Murphy-White, Future Orchards Front Line Advisor, Pomewest; Dr Sally Bound, Senior Research Fellow, TIA.
Acknowledgments
We thank Steven and Ugo Tomasel (Qld), Maurie, Ann, Tim and Michelle Lyster (WA) and Scott Price (Tas) for the use of their orchards in this trial.
This research was conducted under the project AP12029 Understanding apple and pear production systems in a changing climate, funded by Horticulture Innovation Australia Ltd using the apple and pear industry levy paid by growers and matched funds from the Australian Government.
Additional financial support was provided by the Department of Agriculture and Fisheries, Queensland (DAF); Pomewest; and the Tasmanian Institute of Agriculture (TIA).
See this article in Tree Fruit September 2016
