Use of thinners can increase the fruit size of blueberries in an evergreen system

ABSTRACT

In Australia, small and sour fruit can be a problem for growers of southern highbush blueberry (Vaccinium corymbosum L.) during the early season. A field experiment examined the impact of hand thinning and the foliar treatments, urea, ammonium thiosulphate (ATS), benzyladenine (BA) and ATS/BA combination on blueberry cultivar ‘OB1’ fruit quality for an entire season. Treatments were applied over four weeks from the first harvest. Urea (5%) and ATS (0.78%) were effective at desiccating open flowers. However, BA (0.015%) failed to thin fruit, applied alone or following ATS. Fruit size (berry weight and diameter), increased towards the end of the season without compromising yield for hand thinning, ATS, BA and ATS/BA. However, thinning had no effect on the concentration of total sugars or acids. Foliar urea, although an effective desiccant, had little effect on fruit size, and despite its use to reduce leaf senescence in autumn, it had no effect on the leaf canopy area. Future research should evaluate earlier applications of ATS and BA for increasing fruit size early in the season when fruit weight and diameter are most limited.

KEYWORDS:

• Vaccinium corymbosum
• leaf area index
• titratable acidity
• brix
• total soluble solids

Acknowledgements

The authors would like to acknowledge Lorraine Spohr’s contribution to the experimental design and data analysis. Joshua Jarvis, Carly Murray, David Robertson and Mark Bullot provided technical support. The authors would also like to thank Gurmesh and Satpal Singh for the use of their blueberry crop within this project. The valuable comments received from the anonymous referees allowed us to greatly improve this manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was a co-investment made by NSW Department of Primary Industries, Berries Australia and Horticulture Innovation Australia Limited (project code: BB14002).