Winning blackgrass war

20 February 1998




Winning blackgrass war

In this special focus we track progress of herbicide-

resistant sugar beet, assess cleavers mapping and

check latest thinking on weed control in peas and

cereals. We begin with views on new grass weed

herbicides in the pipeline. Edited by Robert Harris

HERBICIDES which offer as good or better control of blackgrass in cereals than current standards are on trial across the UK.

Three products look especially useful, says Profarma agronomist Stuart White. Flurtamone, already approved and test marketed on a limited area last autumn, is Rhone-Poulencs offering.

JV 485 is a pre-emergence chemical from Twinagro, a Monsanto/Bayer joint venture company, and Cyanamid has an un-named product in the trials too. All have different modes of action from each other and existing herbicides.

All are being trialled alone or in sequences and mixes with other products, including Avadex (triallate) and ipu. Two of the 10 sites contain suspected resistant blackgrass to provide the toughest test.

Four standards, also applied alone or in various mixes and sequences, are providing the benchmark against which the new chemistry will be judged.

Lexus Class (flupyrsulfuron-methyl + carfentrazone-ethyl), available for the first time last autumn, is one of those standards. The others are Hawk (clodianfop-propargyl + trifluralin), Cheetah (fenoxaprop-ethyl) and Topik (clodinafop-propargyl).

Lexus Class looks to be the equal of ipu, but at £30/ha (£12/acre) it is twice the price, says Mr White. "And it has little effect on resistant blackgrass – its the equivalent of a Topik or a Cheetah."

Applying Stomp (pendimeth- alin) beforehand improves control. But it is not the easiest programme to manage, he points out. "The Stomp has to be on before the blackgrass emerges, and it wont do a complete job."

Flurtamone looks a better bet, he believes. "We have applied it post-emergence and in mixes with ipu. It is thought of as a replacement for ipu but it also has very good activity on other broad-leaved weeds, notably cleavers when used pre-emergence."

The product was sold in a three-way mix last autumn, with diflufenican (DFF) and ipu. "At the recommended rate you put on 100g/ha of DFF. Thats far too much. We want to be able to tailor rates, especially as flurtamone has good cleavers activity."

Mr White advised grower Paul Turnham to spray a field of winter barley at Astwell New Park Farm, Syresham, near Brackley, with the new product. The thick blackgrass which is resistant to fops was sprayed in mid-October with 3.75 litres/ha of the three way mix.

That provided 101g/ha of diflufenican, 1500g/ha of ipu and 251g/ha of flurtamone for £40/ha (£16/acre).

"Using ipu and Hoegrass we would normally expect a 50% kill in this field," says Mr Turnham. He estimates the new mix has upped that another 10%, although speed of kill was slower.

"I would hope to kill at least 80% of the survivors with a follow-up Tigress + ipu mix," says Mr White.

He believes growers will benefit most from flurtamone in mixtures. "If we could mix and match we would knock at least a quarter off the price."

On a trials site at Great Worth Hall, near Banbury, Northants, up to 95% control has been achieved on hard to kill but thinner blackgrass, he notes.

The other two products are giving at least as good control, says Mr White, who is bound by secrecy agreements with manufacturers. "JV 485 was applied pre-emergence, but we have not had to overspray yet. Suffice to say both products are giving the sort of control levels we saw before the onset of resistance."

NEW BLACKGRASS PRODUCTS

&#8226 Flurtamone from Rhone-Poulenc. Contact residual, offering ipu-like control. Good on cleavers.

&#8226 JV 485 from Twinagro. Pre-emergence material offering good control of blackgrass.

&#8226 Cyanamid product also in trials.

NEW BLACKGRASS CONTROL

&#8226 Flurtamone from Rhone-Poulenc. Contact/residual, offering ipu-like control. Good on cleavers.

&#8226 JV 485 from Twinagro. Pre-emergence material offering good control of blackgrass.

&#8226 Cyanamid product also in trials.

Paul Turnham (right) and Stuart White have achieved better blackgrass control with flurtamone although speed of kill appears to be slower.


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