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 (foramsulfuron + thiencarbazonemethyl) 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 blackgrass. 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.
“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.
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.
“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.