More thoughtful weed control - cpm magazine
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More thoughtful “ We still
have essentially
weed control the same set of
active ingredients
we’ve had for
decades.
”
Roots Sugar beet
weed control
This spring the desmedipham need a little more thought this year. treatment to provide flexibility to post-em
Unfortunately, the choice of pre-em applications and on land with a high weed
co-formulations that covered herbicides is currently somewhat limited burden (either in terms of difficult to control
a lot of the bases when it as a result of the revocation of chloridazon species or sheer population of weeds).
and the removal of pre-em usage from the Bayer launched Betanal Tandem
came to making weed control lenacil label. (phenmedipham+ ethofumesate) last
recommendations are no month, though to many agronomists
Filling the gap it’s a product that’s already extremely
longer available, so it’s back “Thankfully, Goltix and Goltix Titan are well-known having been originally
to basics. CPM looks at the more than capable of filling the gap, with launched in 1986 and used for a good
the inclusion of quinmerac in the latter number of years before being superseded
take on the situation from providing excellent protection against by several co-forms which included
industry and in the field. several of the more difficult to control desmedipham.
weeds such as cleavers, orache and “Betanal Tandem offers greater ease of
By Lucy de la Pasture bindweed.” use over straights and is approved for use
Because modern sugar beet varieties with Dow Shield (clopyralid) and Goltix,
are so quick to germinate, pre-em which will help to extend its flexibility in
There’s a lot of talk from the manufacturing herbicides should ideally be applied tackling volunteer potatoes and mayweed,”
▲
side of the industry about the loss of the within 24-48 hours of drilling and certainly
contact herbicide desmedipham, which is within an absolute maximum of five days
now beyond its use-up period after its post-drilling, he adds.
withdrawal was announced in 2019. Bill recognises there might be some
Dr Bill Lankford, herbicides technical reticence in terms of adding a pre-em to
specialist at Adama, believes 2021 could spring herbicide programmes –– due to the
be the year when there’s a resurgence in additional input cost, extra workload and
the use of pre-emergence herbicides such the need for adequate soil moisture to
as Goltix (metamitron) and Goltix Titan make pre-ems work effectively –– but he
(metamitron+ quinmerac). believes that the pros often outweigh
“With desmedipham no longer available, the cons.
sugar beet growers aren’t entirely able to “Crucially, the inclusion of a pre-em
depend on post-emergence treatments treatment as part of a wider weed control
alone to achieve the necessary level of programme can significantly improve final
Bill Lankford reckons the use of pre-emergence
weed control,” he suggests. crop yields,” he explains.
herbicides may see a resurgence this season.
“Herbicide programmes will therefore He suggests considering a pre-em
86 crop production magazine march 2021
Potatoes
have reached fully expanded cotyledon
stage.
“The need to control flowering weeds
such as field pansy should not be
overlooked. We expect most growers to
deploy Betanal Tandem across two or three
applications and, in some cases, with a
residual, so this should give growers good
opportunity to comply with the conditions
of the emergency authorisation for Cruiser,
if it comes into effect,” she says.
Bolster control
Bayer is reintroducing old stalwart Betanal Where mayweed is present, Bayer
Tandem to take the place of its coforms which advocates the addition of Goltix in a mix
contained desmedipham. with Betanal Tandem plus oil. “This will also
bolster control of other weed species, such
says Lizzie Carr-Archer, Bayer campaign as runch, cleavers, hemp-nettle, annual
▲
manager for root crops. meadowgrass, pale persicaria, redshank
“Trials demonstrate that Betanal Tandem and ivy-leaved speedwell.”
gives better control of a range of weeds Sugar beet weed control traditionally relies on
The view from the field doesn’t
than a comparable mix of straights and is phenmedipham for contact activity in tank-mix
necessarily reflect the same concerns
also safer to the crop. It has outperformed with low doses of residuals herbicides.
about weed control without desmedipham
other two-way formulations in trials, most .co-forms, which have historically been
notably on fat-hen, black-bindweed, small used more by service distribution and good crop safety and life will get more
nettle and annual mercury.” agronomists, says AICC member complicated –– it means thinking more
Bayer recommends the addition of an Andrew Wells of Arable Alliance. about tank-mixing and the ratios of the
adjuvant oil such as Mero, a methylated “There may be a lot of wringing hands different active ingredients required.
rapeseed oil, and a first application timed in anguish at the loss of products which “Many agronomists in the independent
for when the majority of the crop plants provided broad-spectrum weed control sector have always used straights. Mike
▲
More contact for fen soils
The loss of desmedipham from the sugar beet component in Betanal MaxxPro (ethofumesate+
herbicide armoury has meant some growers and phenmedipham+ desmedipham+ lenacil) ––
agronomists are reconsidering their control planning herbicide strategies takes more thinking
options. One of these is Lincolnshire farm about,” he says.
manager, Terence Riley, who says keeping on “Yield is king with sugar beet. We start lifting in
top of weeds is a prerequisite to producing a Sept on the heavy land at JEG Farms, near Spilsby,
profitable sugar beet crop. when average yields are about 55t/ha. It’s a
The average yield across his farm is a compromise between losing some yield and being
respectable 80t/ha on soils ranging from heavy able to get back on the land in the autumn in good
loams to black peat. As a result of the range in time to drill first wheat, before the wet weather
soil types, weeds are broad spectrum and high stops land work. Black fen soils are the last
in numbers. A reducing armoury of products only to be lifted and yields on these can reach up
exacerbates an already challenging situation, to 105t/ha.”
he believes. The virus yellows situation last year had a big Terence Riley is adapting his approach to weed
Traditionally he would use the FAR approach impact and reduced yields on one field to 22t/ha. control on his black fen soils, which can lock up
to help tackle the plethora of weed species, “Clearly yield reductions at that level are not residual herbicides, to include Debut for more
particularly on the black organic soils where a sustainable and so everything that can be done contact activity in his programme.
protracted germination period makes some to protect yield must be done.”
species particularly difficult to control. The revocation of desmedipham has given “This year we will apply Debut slightly later
“I’m not convinced residuals on our black Terence an opportunity to reassess and restructure than before –– just after cotyledon stage ideally
organic soils don’t get locked up and if it’s dry the farm’s approach to controlling weeds. This has –– to ensure more weeds have germinated and
too, then weed control can be seriously seen a move away from his traditional system to a that there’s a bigger weed target area,” he says.
compromised. In the past we would always buy different approach using only two applications, “Relying on contact material loses some
our sugar beet herbicides with all the actives based on Debut. flexibility, which makes timing more critical. In the
necessary to control weeds in one can. Historically, the herbicide programme was past we used residual actives to sensitise and
“It was easy and didn’t take much thinking based on Betanal MaxxPro plus Goltix tank-mix. weaken weeds for the contact material to then
about. Because we have lost several actives This provided the depth of actives to tackle most kill them. But contacts used correctly can do a
–– the most recent being desmedipham, a weeds, he says. perfect job of taking out weed competition.”
88 crop production magazine march 2021
Potatoes
May was inspirational when under pressure with decreasing appropriate for the weed
▲
he was at Brooms Barn and profit margins so we have to do species present in field, being
gave us the confidence to put all we can as agronomists to built up through the programme.
together tank-mixes that can be keep input costs down while “I usually add a low dose
tweaked for a wide range of optimising yields to help of ethofumesate to the first
different conditions.” growers generate more profit herbicide application as it
The reality of the herbicide from the crop.” provides a little extra contact
situation in sugar beet, as activity in addition to
Andrew sees it, is that actually Building blocks phenmedipham and metamitron
very little has changed. “We still As well as the same building is often my residual of choice.
have essentially the same set of blocks for herbicide pro- The second application is
active ingredients we’ve had for grammes, the principles behind usually a similar mix, with lenacil
decades. Desmedipham had using low doses of herbicides where brassica weeds are
some quirky strengths on for weed control in sugar beet present. I only tend to reach
some weed species but didn’t also remain unchanged –– with for Debut (triflusulfuron-methyl)
really add much for the weeds phenmedipham being the major if the weeds present are
in my Nottinghamshire area,” component to provide contact bigger. Essentially it’s a FAR
he comments. activity and then a residual (phenmedipham –– activator ––
Andrew Wells says that by using
“Sugar beet is a crop that’s component, made up of actives residual) system but with doses
straights it can help keep input costs
adjusted for a 10-14 day interval
down while optimising yields to help
rather than every 5 days as in
growers generate better profit from
true FAR style.”
the crop.
Desmedipham also brought
better contact activity than
phenmedipham under cooler or need to remove a barley cover
drier conditions but Andrew has crop before it gets competitive
found that judicial use of an with the sugar beet,” he says.
adjuvant oil aids penetration of “In practice, Falcon
the herbicide into the weed (propaquizafop) is tank mixable
when that bit of extra activity whereas Centurion Max
is required, particularly when (clethodim) has to go on alone
it’s dry. and you need to allow a spray
“The biggest challenge can interval before and after
Grassweed control can sometimes compromise broadleaf weed control be fitting a graminicide into the application, which can
timings but often fits in between the second and third post-em applications. programme, particularly when compromise broadleaf
the timing is dictated by the weed control.” ■
Odds against for Cruiser derogation
According to BBRO, the wintry cold snap in Feb Feb, according to BBRO.
had a significant impact on overwintering aphid “This is one of lowest average temperatures on
populations, both reducing their numbers as well record for many years and below the average
as the date of their migration into the 2021 crop. recorded in 2018 (‘Beast from the East’ year).
It’s also expected that virus infection in 2021 will 2018 is a good benchmark comparison for what
be significantly lower compared to 2020 as a we can expect in 2021. The virus yellows forecast
result, proving that freezing weather is one of the (without neonic seed treatment) was for 6.5-9.8%
best insecticides. of the crop to be affected, depending on drilling
The trigger for an emergency authorisation for date and factory area. As 2021 is colder, there will
Cruiser seed treatment hinges on the outcome of likely be a greater suppression of aphid
the Rothamsted Research virus model, which numbers than in 2018.”
The latest from BBRO is that the Rothamsted
predicts the proportion of the crop which will be Reacting to the news, Andrew Wells says he’s
model is looking unlikely to trigger the
infected by virus yellows at the end of Aug. The fairly relaxed about it. “Some of my sugar beet
derogations for use of a neonic dressing on
decision on whether the 9% threshold has been growers were going to go with 50% neonic-treated
beet seed this season.
reached will be made on 01 March but the BBRO seed and 50% without, because of either following
prediction is that there’s an 84% chance that the crop reasons or because the neonic treated seed
derogation won’t come into effect this season. is going to arrive so late on farm. lighter land then we may or may not need an
Historically, temperatures in Jan and Feb “We have to trust the science and the insecticide, depending on how much later aphid
have been shown to be the most closely Rothamsted model has been well tested and very migration in to crops happens.”
related to aphid numbers and virus levels. accurate over a good number of years. If we don’t The bigger issue will be to minimise the threat
To date (mid-Feb), a current average temperature need the neonic then that’s great. If we can get of virus carry-over from local sources, so good
of
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