Home' Cherry Magazine : Cherry spring 2018 Contents FRUIT SET
horticulture.com.au/grower-focus/cherry | Spring 2018
REASONS TO USE
DORMANCY OR ‘REST
1. To compact the flowering period,
especially for cultivars prone to extended
flowering periods when their chill
requirement is not fully satisfied.
2. To synchronise the flowering period of
3. To advance flowering and harvest in
order to obtain a marketing advantage
and possible premium price, but this
strategy requires mitigating against the
risk of frost damage.
4. To promote flowering and vegetative
bud break due to insufficient chilling
that otherwise causes reduced fruit set
and fruit quality, delayed foliation and
extended bloom periods.
Rest Breaking Agent
Calcium ammonium nitrate (CAN17)
Risk of toxicity if applied less than 3
weeks before budbreak. May advance
bloom by 5–7 days and harvest by
Erger®+ Activ Erger®
Apply 45 (± 5) days before bud break
(5% of green leaf tips visible). Early
applications (prior to 45 (± 5) days
before bud break) are less effective.
Late applications (later than 45 (± 5)
days before budbreak) are also less
effective and increase the risk of
Rate: Erger 6% + Activ Erger 8% (www.
plantdormancy.net) Thoroughly wet the
branches (it is advised 1000–1500L of
solution per hectare depending upon
the equipment used and plant size).
Do not use other RBAs in the same
Do not use on trees less than 4 years
Used mainly for compacting bloom.
Less effective than other treatment
options in advancing bloom.
Paclobutrazol (Cultar AuStar, Payback) 2 applications: just prior to bud break
and just after harvest.
Pre-conditioning treatment for
cherry trees to enhance bud break
and fruit quality. Use recommended
Paclobutrazol® rates for cherries and
adjust for soil type and vegetative
growth rates. Rates have to be
adjusted as Paclobutrazol® is highly
effective when applied as a collar
drench and watered in.
Potassium nitrate and zinc
Weekly applications of potassium
nitrate for 1 month prior to normal leaf
drop followed by a final spray of zinc
Pre-conditioning treatment for
cherry trees to enhance bud size,
bud break and fruit quality. Marginal
leaf burn will occur with potassium
nitrate sprays. However, bud size is
increased in stone fruits. Zinc sulphate
spray will burn off the remaining
leaves. Buds appear to be stronger
and enter their dormancy phase in a
35–50 days before budbreak
Plants appear to enter a deeper
dormancy after application, but the
Waiken® application results in an
enhanced bud break and flowering
Source: Australian Cherry Production Guide 2017. Chill and heat requirements: From dormancy to flowering.
“There is a bit of magic involved in
getting the timing right since we can’t see
into the tree to see where it is at growth-
wise,” Dr Darbyshire says.
RBAs that are applied too early will have
little effect – an expensive mistake. If they
are applied too late, some compounds exert
phytotoxic effects. Growers are also advised
to work closely with their agronomist when
learning to use these materials.
Mr Chapman says he is not a big fan of
RBAs. “I found I get inconsistent results with
the use of dormancy breakers, so I decided
not to use them unless impacts on yields
from insufficient chill become a major issue.”
He adds that RBAs have a role in orchards
where cross-pollination between varieties is
required for fruit set. Then RBAs are useful
to synchronise flowering time by speeding
up bud break in the later-flowering cultivar.
A growing concern
RBAs could also come into increased
play should weather patterns continue to
become more variable. Mr Chapman’s nine
years of CP data confirms that seasons are
becoming more erratic, as noted by many
growers and agronomists across agricultural
sectors. “The increase in variability we see
with regards to which months are cold
and the occurrence of warmer spells – is
amazing,” he says.
To better understand the consequences
of climate variability, Dr Darbyshire has
modelled the possible decline in chill
accumulation associated with climate
change scenarios. Among lead sites already
experiencing impacts occasionally are
locations in Western Australia. Her forecasts
in the form of CP maps – have been
published and a summary of the findings
can be viewed online (https://tinyurl.com/
Further information on RBAs is available
in the report Chill and heat requirements:
From dormancy to flowering authored
by Charlotte Brunt (of Cherry Growers
Australia), Dr Darbyshire, TIA’s Robert Nissen
and Steve Chapman. It can be downloaded
Dr Rebecca Darbyshire,
Mark Chapman, email@example.com
Table 2. Risks and benefits associated with various dormancy breaking strategies.
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