F
Sof t
f
rui t Day
F
T
he
frui
TG
rower
• JAN
u
A
r
Y2017
blackcurrant sawfly. Both pests canweaken bushes and
attacks can be sporadic and localised, so identifying their
pheromones tomake commercial traps available in the future is
a breakthrough.
f
utureworkwill look at usingpheromone
blends in reddelta traps and investigating the relationship
between trap catches, infestation, foliage damage and
numbers of natural enemies.
e
arwigs are often overlooked as friends to growers, and
MaddieCannon and a team at N
i
AB
e
M
r
, assistedby
h
arriet
r
oberts of L
r
Suntory, have been surveying the role of earwigs
for pest control in blackcurrants. 50plantations around the
countrywere surveyed using earwig refuges deployed inApril
andMay.
w
ith the loss of actives likeAphox therewill be a
higher reliance on natural enemies in future. Thiswork is a first
step towards determiningwhat predator types and numbers
are needed to control pests of blackcurrants belowdamaging
thresholds.
Other pests
TomPope of
h
arper Adams
u
niversity reported new
research intopotato aphid control on strawberries. This follows
on fromProject S
f
140which indicated the potential
importance of spray coverage and identified
h
allmark as giving
good control, but which is not
i
PM friendly. So, although
autumn clean-up sprays are useful, what intervention in spring
will help?
w
here are the aphids andwhy can’t we control
them?
o
verall aphid numberswere highest on the lower leaf
surfaceswithmoderate numbers on leaf stalks and in the
crowns. At flowering the highest numberswere on the flower
stemswith lowest numbers on the petals.
i
n a polytunnel trial
h
allmark effectively controlledpotato aphidwithin three days of
treatment on overwintered strawberry plants, whereas other
treatmentswithChess andCalypso all allowed aphid numbers
to recover or just didn’t work. The use of Silwet wetter did not
improve control.
h
owever, in a leaf dipping assay
h
allmark and
Calypsowere effective against potato aphid, either when
aphidswere placedon sprayed leaves or when theywere
sprayed, and that Chess plus Silwet wetter wasmore effective
when aphidswere directly sprayed. Growers are left with
limited options as
h
allmark is incompatiblewith
i
PM.
According to JudeBennison, another thrips species has
been identified that causes fruit bronzing symptoms in
strawberries but is not controlledby the
i
PMmeasures to
overcomewestern flower thrips (
wf
T).
i
t is a native species
Thrips fuscipennis
– commonly called rose thrips, and are
much darker than
wf
T. This ‘newpest’ of strawberry is being
monitoredby theADAS fruit team and growers are being
asked to look out for dark thrips in flowerswhere fruit damage
is seen. More information is required to find out how
widespread it is andmore about its biology andwhy
i
PM
programmes based on
N. cucumeris
are not controlling rose
thrips.
◆
12
w
ater drainage fromopen growing systems often causes
significant environmental pollution, due to the use of
agrochemicals, and leads to the loss of water and nutrients.
A team of SouthKorean scientists investigated the potential
application of an irrigation schedule basedon previously
determined threshold values of volumetric substratewater
content to improve strawberry variety Seolhyang on a
commercial farm (
Horticulture, Environment, and
Biotechnology
).
The aimwas to improvewater and fertilizer delivery in a
coir substrate system using frequency domain reflectometry
(
f
D
r
) sensor-automated irrigation.
f
or comparison, a
conventional fixed timer-based irrigation treatment was also
used.
A significant decrease in irrigation volume occurred in the
automated
f
D
r
system, due to a reduceddrainage ratio,
whereas using a timer led to the consumption of large
amounts of nutrient solution. Theweekly irrigation volume
per plant for the
experimental period
averaged370ml for the
f
D
r
system and666ml for
the timer-based system,
with theweekly drainage
volume per plant averaging
55.8ml and 300ml respectively. The total irrigation volume for
the timer systemwas 70% higher, while therewas no
significant difference in the total retained volume in the
substrate between the two treatments during the
experimental period, which led to a 20% higher water use
efficiency under
f
D
r
. Plant growth, fruit yield, and soluble
solid content did not significantly differ between irrigation
methods.
The volumetricwater contents in the substrate ranged
from 58% to62% and from 63% to 65% for
f
D
r
and timer,
respectively. The
e
C level of the substrate solution
byDr DavidPennell
r
esearchBriefing
i
mprovingwater and fertilizer delivery in
strawberries using
f
D
r
sensor-automated irrigation
