Smart beet weed control system a hit – Arable Farming – Darryl Shailes, Edmund Stevens

Launched a year ago, the Conviso Smart system has shown good results in its first season ...

This is despite a spell of hot, dry conditions, which do not favour herbicide activity, in the early part of the growing season.

Conviso Smart comprises a broad-spectrum herbicide product, Conviso One (foram-sulfuron + thiencarbazone-methyl) and varieties tolerant to its active substances.

The ALS herbicide product offers contact and residual activity against a range of weeds, including fat hen, cleavers, volunteer potatoes and sensitive grass-weeds, including black grass. It also kills weed beet.

The system has been distributed for the 2020 season by Hutchinsons and Frontier.

Darryl Shailes, Hutchinsons root crop technical manager, says: “Two varieties are available, Janninka and Rivetta, but we dismissed Rivetta on its bolting risk, which is the highest of all varieties on the Recommended List.”

Chris Piggott, Frontier regional seed manager, says 1,800 hectares of Janninka has been grown by the company’s customers.

Effective

“Just under 100 growers were on contract to grow Janninka. These have been predominantly good beet growers, particularly those with parts of the farm where there were weed beet issues or issues with broad-leaved weeds where Conviso is effective.

“Growers are bringing fields where they haven’t been able to grow beet back into production. Results have been pleasing, says Mr Piggott.

“I’m very pleased with how it’s performed. It has been quite a test this year, particularly the dry period of weather which doesn’t always favour herbicide activity. It has been a pleasant surprise in terms of the weed spectrum it has covered and how persistent it has been.

“There have been no surprises in relation to the label on what it did or didn’t do, and it has done a good job on weed beet. It has also been quite strong on late-emerging weeds.”

Mr Shailes says the system promises to give growers greater flexibility around early spray timings and help mitigate the impact of losing vital chemistry, notably desmedipham, which could make weed control much more challenging next season.

“It’s not just the loss of desmedipham that’s an issue, but the fact we’ve also lost modern formulations, which means weed control is going back to basic formulations of older active ingredients that don’t give the same efficacy,” says Mr Shailes.

Darryl Shailes

The optimal timing for Conviso One is at two to four true leaves of weeds, predominantly fat hen, which is used as a marker weed.

While a single application of the spray is needed in theory, the weed control programme will depend on weed pressure and on individual farm situations regarding weed populations, which will influence whether a holding spray is also applied, says Mr Piggott.

Confident

“We are becoming more confident in using Conviso as a herbicide in its own right and unless there is high weed pressure, shouldn’t need to apply much of anything else, if anything at all.” The product has also shown good crop safety, says Mr Piggott.

“The crops are looking very good and crop safety is good – it has not knocked sugar beet.”

Norfolk-based Hutchinsons agronomist Edmund Stevens acknowledges there is a slight yield penalty associated with the herbicide tolerance trait, 11% for Janninka, but insists this is more than compensated for by the yield benefits from improved weed control.

He says: “With a severe infestation of weed beet, you could be looking at anything up to a 20-30% yield loss in the worst cases. Yes, there is a few per cent yield drag in tolerant varieties, but that’s virtually irrelevant when you consider the alternative of not growing a Conviso variety.”

Looking ahead, Mr Shailes says more Conviso varieties are being developed and the commercial applications of the system are likely to expand beyond regular weed control. For example, work is underway to investigate how Conviso varieties can be grown alongside companion crops, using the Conviso One herbicide to take out the companion crop when required, which may benefit virus control.

There may also be benefits for terminating cover crops where they are grown to prevent soil erosion on light land, he says.

In the field:

Tom Pearson, arable farm manager, Raynham Estate, Norfolk

Tom Pearson is using the Conviso Smart system on a field where the beet rotation was skipped last time due to high weed beet pressure. “It seemed the ideal candidate field for a trial,” he says. “We have grown 30 hectares of Janninka this year.”

The field was drilled on April 6 at a seed rate of 105,000 seeds/ha. The crop had a standard pre emergence herbicide application of 1 litre/ha of Goltix (metamitron), followed by a post-emergence application of 0.75 litres/ha of Betanal maxxPro (desmedipham + ethofumesate + lenacil + phenmedipham), plus 0.75 litres/ha of Goltix at two true leaves of the crop.

“This helped us to keep problem weeds in that particular field, such as fat hen, knot-grass and bindweed in check, allowing for a more effective and well- timed application of Conviso One,” says Mr Pearson.

A single application of Conviso One was made on May 25 and no further herbicides were applied after this.
Mr Pearson says: “It gave excellent control of fat hen at three to four true leaves, as well as large bindweed plants. Any weed beet present in the field at the time, regardless of size, was controlled with ease.

“Efficacy seemed to be good, despite the dry spring. Uptake and efficiency of conventional chemistry, on the other hand, was very poor this spring.”

Mr Pearson ensured the Conviso Smart field was sprayed last in the programme, to reduce the chance of any application errors across conventional sugar beet. Also, any bolters were pulled immediately as a matter of priority.

Proof

“The crop looks very good, currently. There is an 11% yield loss according to the Recommended List but the proof will be in the pudding come harvest time. The yield loss could easily be compensated for in herbicide savings and improved weed control in a dry spring, particularly with the loss of desmedipham going forward.

“We are planning on growing another 30ha next year on the rotation’s worst weed beet field.

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