New Zealand Journal of Crop and Horticultural Science abstracts
Hydrogen cyanamide impacts on flowering, crop load, and fruit quality
of red ‘Fuji’ apple (Malus domestica)
S. A. Bound
K. M. Jones
Tasmanian Institute of Agricultural Research
University of Tasmania
13 St Johns Avenue
New Town, TAS 7008
Australia
email: Sally.Bound@dpiwe.tas.gov.au
Abstract The extended flowering period of many apple
(Malus domestica) cultivars often causes problems in the management
of crop load. Hydrogen cyanamide (Dormex®) was examined over a 2-year
period for its effect on flowering, crop load, fruit size, and quality of
‘Fuji’ apple. In Year 1, hydrogen cyanamide was applied at 5 application
times (40, 30, 20, 10, or 0 days before estimated budburst (dBEB)) at 3%
v/v. These treatments were compared with an untreated control. In Year 2,
hydrogen cyanamide was applied at 1%, 2%, or 3% v/v at either 40 or 30 dBEB.
The blossom thinner ethephon was applied to all hydrogen cyanamide treated
trees at full bloom. An untreated control, a hand-thinned treatment, and
a chemically thinned control were also included. Hydrogen cyanamide advanced
flowering in both years when applied at 40 or 30 dBEB. In Year 1, full bloom
was advanced by more than 1 week and the flowering period from pink bud to
full bloom compressed by the 40 dBEB application, resulting in a very clearly
defined full bloom date. Application of hydrogen cyanamide at budburst or
10 dBEB resulted in extended flower development and some bud scorching. Unseasonally
warm spring weather conditions in the second year resulted in an abnormally
short flowering period. It would appear that under these conditions hydrogen
cyanamide can still be used to advance flowering but is not necessary to
compress the flowering period. Hydrogen cyanamide reduced fruit set in the
first year but not the second. Most treatments showed no detrimental effect
on fruit quality. There was no evidence of any negative interactions between
HCN and ethephon.
Keywords dormancy; phytotoxicity; chemical thinning;
ethephon
H03105; Received 20 November 2003; accepted 28 January 2004 ; Online publication
date 15 June 2004
New Zealand Journal of Crop and Horticultural Science, 2004, Vol. 32:
227-234
0014-0671/04/3202-0234 $7.00 © The Royal Society of New Zealand
2004
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