| Arable
Pod protection to stop larvae
losses
Max Newbert
With most oilseed rape well through flowering, growers should now be on the lookout for Seed weevil activity.
ome hard late April
frosts across large
parts of the country
could result in
some early pod
abortion on
flowering raceme, so protecting
remaining pods will be essential
for crops to make best use of this
season’s high potential.
S
“If you can prevent that initial
pod damage it will also
minimise the impact of Pod
midge”
Cabbage seed weevil make a
hole in a pod to lay an egg, but
which then allows the Pod midge
to access the pod laying several
eggs per pod and up to 60 eggs in
their lifetime. The resulting feeding
larvae can be far more damaging,
warned Syngenta Insecticide Field
Technical Manager, Max Newbert.
Max pointed out that the Seed
weevil itself causes relatively little
damage, by laying just one egg
per pod, that typically only destroy
one or two seeds per pod.
However, the Pod midge uses the
hole left by the weevil and its
larvae will effectively destroy the
entire pod’s yield by causing pod
shatter.
He highlighted that the relatively
cool April meant Seed weevil
migration from overwintering sites
in hedgerows and margins had
been slow so far, but as soon as
conditions warm up crop invasion
will increase. The threshold for
treatment is just one Seed weevil
per plant for the main OSR
12 | Farming Monthly | May 2017
growing areas.
“Treatments must be timed to
target the adult weevil,” he
advised. “If you can prevent that
initial pod damage it will also
minimise the impact of Pod
midge.” Max advocated Hallmark
Zeon treatment at the full rate of 75
ml/ha would provide an instant hit
on in-crop weevils and repellence
activity to dissuade migration.
“In sunny conditions, the UV
protection of Hallmark Zeon
formulation can give extended
activity and protection of the crop
not seen with other lambda
products,” he added. “That could
prove essential where Seed weevil
migration may go on for several
weeks, and especially this season
where there will be a potentially
beneficial long post-flowering
green crop area.”
The Seed weevil treatment
timing would also give control of
any Pod midge in the crop,
although growers can make a
separate Hallmark Zeon treatment
for Pod midge before the end of
flowering if required. The threshold
assessment for treatment of Pod
midge would depend on the extent
of Seed weevil pod holes.
Pods that have already set on
main raceme will be relatively safe
from frost effects, but side shoots
and later flowering plants may
have been particularly effected,
said Max. A series of warm days
and cold nights appears to be
especially stressful for crops and
could result in poor pod set, he
added.
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