In this issue..

Liquid logic has
a way with
weeds
Iain Learmonth is looking to control aggressive
populations of cleavers and groundsel and
potentially ALS-resistant populations of
chickweed and mayweed.
Technical
Innovation Insight
When Dupont scientists
finally created a formulation
to partner fluroxypyr with
sulfonylurea herbicides, it
wasn’t just the spectrum of
the one-can solution that
was improved. CPM tells
the story.
By Tom Allen-Stevens
Sulfonylurea herbicides have long been
the mainstay of broadleaf weed control in
the spring. Low dose rates and a broad
spectrum make them a farmer friendly
addition bringing cost-effective,
season-long control of a number of
culprits that perennially slip through the
net cast by the autumn residual herbicide.
“
But there have always been a couple
of niggles with them –– cleavers aren’t
controlled by the majority of SUs used in
the spring, and then there’s the bewildering
restrictions on sequencing and mixtures.
The improved
adjuvant properties
of the oil dispersion
formulation resulted
in better weed
control. ”
Running out of steam
“When autumn residual herbicides start
running out of steam we see problems with
broadleaf weeds,” notes Steve Cook of
Hampshire Arable Systems. “And by May
weeds are often large so sulfonylureas can
struggle to provide satisfactory control,
especially of charlock and cleavers which
keep emerging throughout the season.
“We have the option of going back in with
Starane (fluroxypyr) for cleaver control, but
there are other weeds to consider too, so a
product with a broader spectrum is needed.”
There are also restrictions on mixing and
sequencing acetolactate synthase (ALS)
chemistry, he notes, and this can be a
problem, especially for growers where
blackgrass is a target.
“Until now, a maximum
of two applications of ALS
herbicides within a season
have been allowed, which
has restricted the choice of
a spring herbicide when
flupyrsulfuron (FPU) and
Atlantis (iodosulfuron+
mesosulfuron) had been
used as part of an autumn
grassweed strategy,” he explains.
For Scottish agronomist Iain
Learmonth, the ability to successfully control
aggressive populations of cleavers and
groundsel and potentially ALS-resistant
populations of chickweed and mayweed,
has become even more important. He
advises for Gardiner ICM, consulting on over
9000ha of a fertile ribbon of land stretching
from just North of Aberdeen to the Black Isle.
Winter cereals constitute the bulk of
his cropping with oilseed rape and
potatoes as a break. While pre and early
post-emergence herbicides have afforded
satisfactory control, there are limited
opportunities to use these, and weeds such
as chickweed often slip through the net.
““I often find myself recommending an
extra application after growth stage 32 to
clean up the crop,” he says.
Weeds such as pansy, hemp nettle,
mayweed and polygonums are perennial
challenges for him. “SUs are very useful at
what they do, if used sensibly, in terms of the
broad spectrum of activity they have and
their ease of use –– if you apply an SU, you
can usually be confident you’ve plugged
any gaps.”
28 crop production magazine arable extra march 2017