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RESEARCH ARTICLE
Contents Vol 44(9)

Ammonium thiosulphate as a blossom thinner of ‘Delicious’ apple, ‘Winter Cole’ pear and ‘Hunter’ apricot

S. A. Bound A B and K. M. Jones A
+ Author Affiliations
- Author Affiliations

A Tasmanian Institute of Agricultural Research, University of Tasmania, 13 St Johns Avenue, New Town, Tas. 7008, Australia.

B Corresponding author. Email: Sally.Bound@dpiwe.tas.gov.au

Australian Journal of Experimental Agriculture 44(9) 931-937 https://doi.org/10.1071/EA03161
Submitted: 7 August 2003  Accepted: 5 December 2003   Published: 22 October 2004

Abstract

The efficacy of ammonium thiosulphate as a blossom thinner of ‘Delicious’ apple, ‘Winter Cole’ pear and ‘Hunter’ apricot in southern Tasmania was assessed. Ammonium thiosulphate at concentrations of 0.3, 1.5 and 4% (v/v) was applied to both ‘Delicious’ apple and ‘Winter Cole’ pear trees at 20% bloom, 50% bloom or full bloom. At 4%, ammonium thiosulphate proved to be phytotoxic to both crops, resulting in the severe burning of foliage and flowers and also bud death. At 1.5%, ammonium thiosulphate reduced the crop load to an acceptable level without excessive damage. The 0.3% concentration was ineffective regardless of time of application in ‘Delicious’ and at 20% bloom in ‘Winter Cole’. Russet incidence was increased on ‘Delicious’ by the highest concentration applied at 20% bloom. Shoot number increased in some treatments, however there was no effect on return bloom. When ammonium thiosulphate at 2.0% was applied to ‘Hunter’ apricot at 20, 40, 60, 80 or 100% bloom, fruit set was reduced regardless of time of application. Ammonium thiosulphate also improved return bloom of ‘Hunter’ apricot.

Additional keywords: fruit set, fruit quality, phytotoxicity.


Acknowledgments

Ferro Corporation (Aust.) Pty Ltd, Chemicals Division are acknowledged for provision of funding for this work and supply of the ATS. Thanks also to Mr David Jennings for technical assistance.


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