Herbicide-tolerant sugar beet draws growers amid high costs – Farmers Weekly

Originally launched ahead of the 2020 growing season, Conviso Smart sugar beet is the result of a collaboration between plant breeder KWS and agrochemical specialist Bayer Crop Science.

It consists of two components – an actolactate synthase (ALS) inhibitor herbicide-tolerant sugar beet variety and a specially developed post-emergence herbicide known as Conviso One.

The growing system was originally targeted at weed beet problems so that growers could bring infested fields back into the rotation. Exploiting the genetics and cutting back to one spray would reduce the number of herbicide applications applied to a crop. This would lead to minimising crop damage, as well as simplifying weed control and reducing workloads, it was claimed.

Two years on and the system is finding favour with growers who are committed to sugar beet. Most sugar beet growers stress the importance of getting the spray timing right, especially in springs where weed emergence is protracted.

Conviso One offers broad-spectrum weed control from just one application of 1l/ha, made at the two to four true leaf stage of the target weeds. This is usually when the second spray of a conventional herbicide programme would be applied.

Crucially, it can only be used on varieties with ALS-tolerance, the first of which was Smart Janninka KWS. Smart Janninka KWS has now been removed from the British Beet Research Organisation (BBRO) Recommended List and replaced by higher-yielding Smart Rixta KWS and BTS Smart 9485.

As a result, keeping accurate records of varieties at drilling and spraying is essential. Active bolter management is also important, with the system best suited to whole field situations.

Initially seen as a very specific tool for a weed beet problem, the subsequent loss of useful chemistry for the sugar beet crop and the rising costs associated with beet growing have changed the way the system is viewed.

As Hutchinsons agronomist Ed Stevens explains, growers in his Norfolk region have adopted the system for various reasons.

These include overcoming a serious weed beet problem to simplifying the job of beet growing, especially when they are covering multiple sites.

“It has allowed fields that weren’t suitable for sugar beet growing to come back into the rotation, and it has delivered a sprayer capacity bonus,” he says.

“It has also replaced the need for hand-pulling weed beet.”

His experience is that growers have found additional benefits as they have gained confidence in the system. These include both volunteer potato and grass weed control, as well as less herbicide damage to crops.

“There is a slight yield penalty, although yields have been better than we had anticipated, as British Beet Research Organisation published yields come from crops grown under a conventional herbicide programme and may not show the safety benefit of using Conviso One on tolerant crops,” he says.

“Making just one herbicide application can be a dilemma, depending on fat hen pressure, with some growers opting to use a holding spray while they wait for the flush of weed beet.”

The additional cost of the system shouldn’t be considered at in isolation, he advises.

“Using one spray instead of four is a saving in both time and money, while the management of the crop becomes much simpler.

“The cost of pulling weed beet has gone up and can be the same as the extra paid for the combined seed/herbicide pack. So it’s definitely worth a closer look.”

Mr Stevens anticipates that the area of Conviso beet being grown in his area will increase from 15% to up to 30% in 2023.

“There are agronomic, environmental and workload reasons for this – every farm is different.”