Agriculture Reference
In-Depth Information
Table
.
Effect of simulated warm and cold spring conditions on fruit set percentage
after hand pollination in 'Cox's Orange Pippin'
Pre-blossom temperature
'Warm Spring'
Ambient
'Cold Spring'
LSD .
Fruit set percentage
.
.
.
.
Data from Jackson
et al.
(). Reproduced with permission.
these are typical of a warm rather than a cool English spring (Table
)
and in Canada fruit set of 'Macspur McIntosh' and 'Summerland' apples was
lower the higher the daytime temperatures in controlled environments over
the range
.
◦
,
◦
and
◦
C (Crowe,
). These effects are not associated
with winter-chilling requirements: in the Canadian study all the trees had
been in cold storage for at least
◦
C)
were the same for all treatments. Effects on ovule longevity and asynchronous
development of flower parts seem to be involved. Evaporative cooling of buds
by water sprinkling also increases set ( Jackson
et al.
,
months and night temperatures (
).
High temperatures at blossom time reduce ovule longevity and can have
adverse effects on initial set. Tromp and Borsboom (
) found that EPP was
extended and fruit set increased when 'Golden Delicious' apples were grown
at a post-pollination temperature of
◦
C. With 'Doyenne
du Comice' pear EPP and fruit set were higher (from February onwards) at
◦
C than at
◦
C instead of
◦
C.
In Akito, Japan heavy early fruit drop, from the
th day after full bloom, of
cvs. 'Starking Delicious', 'Mutsu' and 'Redgold' was found to be statistically
correlated with high minimum temperatures and low sunshine levels around
the
). Controlled environment
studies on 'Starking Delicious' (Kondo and Takahashi,
th day after full bloom (Kondo
et al.
,
) showed that high
◦
C) over the four days starting
night temperatures (
days from full bloom
led to fruit abscission starting
%
under conditions where there was no shed under outdoor night temperatures
(mean
days after treatment, with a final shed of
◦
C). High night temperatures earlier were ineffective and from
to
days after full bloom they induced only
% shed. In subsequent studies
high night temperatures for
days after full bloom were
consistently followed by severe shedding of 'Starking Delicious' fruits whereas
there was less shedding of 'Tsugaru' and in three out of four years none at all
of 'Fuji' (Kondo and Takahashi,
days from
or
).
Studies on fruit set of apples in North America and Europe in relation to
temperatures over different post-bloom periods have given rather variable re-
sults (Dennis,
). They include clear evidence from controlled-temperature
studies that warm temperatures (
>
◦
C) during post-bloom to June drop
