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A big increase in spring cropping this season is expected to give growers a welcome opportunity to boost grass weed control. More spring wheat,... Spring cereals can create more options for grass weed control

A big increase in spring cropping this season is expected to give growers a welcome opportunity to boost grass weed control.

More spring wheat, barley and oats are forecast to be drilled this year after the wet autumn and winter storms left fields unworkable and flooded.

Many growers still have fields unplanted with some established crops rotting in waterlogged soils.

Norfolk-based Agrovista technical manager Mark Hemmant estimates that around only two-thirds of the planned winter wheat area on his patch has been drilled and will be retained through to harvest.

Seed availability and cost will be limiting factors as spring cropping decisions are finalised. Still, spring barley is set to remain the most popular option, not least because it offers an opportunity to get quickly back into a sustainable rotation, explains Mr Hemmant.

“We’ve got an opportunity with spring cereals to invest for the benefit of not only the crop we are planting but future crops,” he says. “You’ve got to think about your rotation as a whole.”

Grass weed pressure would typically be lower in spring cereals than autumn-sown crops, with wild oats as the primary target. But Mr Hemmant says growers must remember that herbicide options are limited.

Label rates for most residual herbicides available for use in spring cereals are below those approved in winter cereals, and products are being lost. Straight pendimethalin, for example, is no longer approved for use in spring wheat.

Wild oats

In situations where wild oats are a problem, or there is moderate to severe blackgrass pressure, or brome or ryegrass are present, pre-emergence residual herbicide Avadex (tri-allate) can be an option.

Avadex provides a solid foundation for weed control in spring wheat and barley, says Mr Hemmant. It gives good control of wild oats and insurance where resistant grass weed populations may limit the efficacy of contact-acting herbicides.

“Brome is an increasing problem and is so competitive; you need every bit of control you can get, and if you’ve got moderate levels or above of blackgrass you’d want to consider Avadex, as well as in ryegrass situations, where we’ve got limited control options.

An application of glyphosate would be the first step in any spring cereals herbicide programme to control weeds already present.

“You would probably apply that as soon as you can travel, followed by another application close to drilling.”

In spring feed barley, there is an opportunity to incorporate either Avadex Factor or Avadex Excel 15G into the a worked or nearly finished seedbed pre-drilling.

It can then be worked in with the drill, says Mr Hemmant.

Depth protection

“It’s a really useful recommendation,” he adds. But this approach is not an option on spring wheat, where depth protection is important.

In spring barley, Avadex Factor can be mixed with glyphosate for incorporation pre-drilling, so long as spray water volume is kept up at about 200 litres/ha. Depending on the crop, a flufenacet-based product can then be applied pre-emergence, mixed with pendimethalin.

Post-emergence herbicide options for use in spring cereals are limited, although Luxinum Plus (cinmethylin) is approved for use in spring feed barley. Good grass weed control in spring crops represents an investment in the entire rotation, says Mr Hemmant.

“If you’re aiming to do the job right, using cultural controls and trying to get lower grass weed levels to start with, Avadex can be the difference between a mediocre job and a really good job.”

With rates the same as those used in the autumn, Avadex Excel 15G granules or the liquid tri-allate formulation Avadex Factor will boost grass weed control in spring and late-drilled winter wheat varieties, as well as spring barley.

This contrasts with some other pre-emergence herbicide options, many of which are restricted to use at around half the autumn label rate in spring, explains Hank King, UK and Ireland business manager for Gowan Crop Protection.

New for this season is the addition of spring wheat to the Avadex Factor label, providing an additional option where growers do not have access to a granule applicator.

Application timing is the same as in autumn-sown crops, says Mr King. This means pre-emergence and as close behind the drill as possible – with a pre-drilling option available in spring barley, he adds.

Excellent job

Wild oats, a key grass weed target in spring-drilled cereals, are highly susceptible to tri-allate, but it will also do an excellent job on black-grass, ryegrass and bromes. Another consideration when controlling wild oats is herbicide resistance.

Resistance to ACCase and ALS chemistry is known to be present in UK wild oat populations, but there is no known resistance to tri-allate, which also brings a different mode of action to herbicide programmes.

Where spring crops are replacing failed autumn drillings this season, care is needed where tri-allate has been used. Where tri-allate has been applied in the preceding autumn, oats should not be planted within 12 months, but spring barley can be safely planted.

For niche market spring crops. Avadex Factor has Extension of Authority for a Minor Use (EAMU) approval in spring linseed, canary grass and corn gromwell (Ahiflower). Avadex Excel 15G has EAMUs for spring linseed and canary grass.

Key advice points

Pre-emergence residual herbicide Avadex (tri-allate) provides a solid, pre-emergence foundation for grass weed control in spring wheat and barley

Addition of spring wheat to the Avadex Factor label new for 2024 harvest season

Option of Avadex application pre-drilling in spring barley (but not spring wheat)

Tri-allate has excellent activity on wild oats and provides good control of black-grass, bromes and ryegrass

No known resistance to tri-allate in UK grass weed populations

Care needed where spring drillings are replacing failed autumn-drilled crops treated with tri-allate – seek professional advice

EAMUs for use of Avadex available in linseed, canary grass and corn gromwell.