HUTCHINSON FieldWise(October2019) - Page 6



Fieldwise
Answers
Is BYDV in winter
cereals a resurgent
challenge?
Duncan Connabeer
Duncan Connabeer (Technical Support Manager) discusses...
As we move into a new cropping
year, no doubt as ever we will
face many new challenges along
the way. In winter cereals, one
challenge that we had thought
we had largely negated, is the
threat of Barley Yellow Dwarf
Virus (BYDV). Many growers may
have forgotten, or may never have
experienced, managing BYDV
without dressed seed, especially
in high risk situations.
The last bad years were 2012 and
2016 which were high pressure and
difficult seasons for BYDV control,
yet all the while 50% of the wheat
crop still had a neonicotinoid seed
dressing. This being our first autumn
without these seed dressings as part
of our armory, we need to be ever
more vigilant of the virus and its
potential impact on crop yields.
A seed dressing provided a 6-8 week
period of protection (from drilling)
through the early emergence phase,
when the impact of virus infection
can be the most damaging. It is a
well-documented fact that earlier
drilling dates will impact the severity
of risk of BYDV. Why? This is because
earlier sown crops are more likely
to emerge in the peak of the aphid
flight. Moreover, seed dressings
provided a useful management tool,
when subsequent treatments may
have been delayed by the weather.
Weather effects
There is also the added implication
of global warming or just seasonal
weather changes of the past few
years, which have seen milder
autumns and winters.
What influence will milder autumns
have on BYDV? It is more a case of
the influence on the virus vectors,
and this is a two-fold effect:
• Firstly, the aphid flights continue
late into the autumn (late
November and even December).
Although I read with interest in
the national press recently, the
arctic conditions last experienced
in the winter of 2017/18 named
the “beast from the east” is being
predicted to return this winter.
• Lower frost intensity, allowing for
aphid survival and multiplication
in crops - populations that would
not normally be an issue which could
potentially cause economic damage.
The trend to later drilling primarily
as a consequence of grassweed
management will help, however it
will still push us to an over reliance on
pyrethroid insecticides, where timing
and frequency of application will be
crucial. The timings of these spray
applications relate to a calculation based
on thermal timing (170-day degrees)
from the first aphids seen within the
crops, aiming to prevent the second
generation of aphids spreading the virus
beyond the primary infection points.
TECHNICAL SUPPORT MANAGER
There are plenty of websites and apps
that will help you with this timing,
based on your own observations and
local weather data. The AHDB website
is but one https://ahdb.org.uk/BYDV.
Finally, do not compromise timings as
a consequence of the opportunity to
tank mix. Also, if aphids are already in
the crop, in periods of extended crop
emergence due to dry soils, do not
wait for full crop emergence, but time
the treatment to the earliest emerged
section of the field.
If you have a question or
challenge about crop production
issues you are facing on your
own farm, please email us:
information@hlhltd.co.uk and put
‘Fieldwise Answers’ in the title.
For more information on any of our products or
services, please contact your local Hutchinsons
agronomist, or contact us at:
H L Hutchinson Limited • Weasenham Lane
Wisbech • Cambridgeshire PE13 2RN
Tel: 01945 461177
Fax: 01945 474837
Email: information@hlhltd.co.uk
@Hutchinsons_Ag
HLHutchinsons
www.hlhltd.co.uk

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