HUTCHINSONS~FieldWise(October2017)w - Page 1

Late Autumn
Weed Control Options
in Oilseed Rape
Oilseed rape remains one of the most useful and profitable combinable
break crops available to UK growers, so it makes economic sense
to optimise yield and profitability. Weed control plays a crucial part in
maintaining yield potential, but with limited herbicide options in the
spring, late autumn offers the best opportunity to get on top of problem
grasses and broad leaved weeds.
Dr David Ellerton (Hutchinsons
Technical Development Director)
looks at late autumn weed
control strategies in oilseed rape
and discusses the best ways
to minimise the environmental
impact of herbicide applications.
Late Autumn
Herbicide Options
Most late autumn options for weed
control in oilseed rape revolve around
two key active ingredients, propyzamide
and carbetamide. Although each active
offers the potential of good grass weed
control (including those resistant to
ALS and ACCase products), both
are very sensitive to environmental
conditions, particularly propyzamide,
which influences whether they achieve
optimum efficacy. Both products give
best control when applied to small
weeds with roots close to the surface.
Propyzamide should be applied from
1st October providing the crop has 3
leaves, although it works best when soil
temperatures are low (8C) and declining
(this improves persistence of control)
and soils are moist (this improves
efficacy). These conditions normally
occur from November onwards.
In contrast carbetamide, being more
water soluble than propyzamide,
can be applied in drier conditions
earlier in the season, although it also
Dr David Ellerton
works best if there is moisture in the
preferably avoiding use if the drains are
To reflect this fact, Crawler (carbetamide)
flowing, or are likely to flow in the near
may be used as a single full dose pre
future. Trials have also shown that the
or post emergence of the crop until the
use of grass buffer strips (12m better
end of February, or as a split dose pre
than 6m) and min till techniques will
emergence, followed by a second split
reduce the amount of product lost by
up to the 3-leaf stage of the crop.
surface run off, or drain flow.
Trials work on adjuvants has also
Further information on water issues
indicated that the addition of silicon
may be found at:
based wetters to the straight products
give a more even distribution through
the soil profile, leading to improved
Grass weeds
efficacy in many cases.
To optimise grass weed control, the
Another consideration when applying
addition of a suitable graminicide such
both these products is that they are
as fluazifop, quizalofop or propaquizafop
frequently detected in water above
to residual products has also been
the limits set under the Drinking
shown to increase consistency.
Water Directive (DWD). Under the
Continue overleaf >>>
Voluntary Initiative, guidelines are
available to minimise the risk of these
actives finding their way into water.
These guidelines show the importance
of balancing the need for spraying in the
right conditions for maximum efficacy,
with minimising the risk of the products
entering water. The key guidelines
for reducing the risk are respecting a
Fieldwise has been allocated
5m no spray zone next to water
2 NRoSO CPD points for 2017/18.
courses, not applying if heavy
your points, please email your full name,
rainfall is expected within
membership number, DOB and the reference number
48 hours and
NO464292f to

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