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Sugar beet: Getting the weed control right – Agronomist & Arable Farmer – Darryl Shailes

Weed control has always been a crucial part of sugar beet production and the consequences of getting it wrong can be very expensive in terms of root yield and overall...

Darryl Shailes, Hutchinsons root crop technical manager, discusses using modern technology to solve the problem.

Data going back several years shows that just one oilseed rape plant per m2 can reduce sugar yield by 500kg ha and two fat-hen per m2 reduce root yield by around 25%. So, getting it right and having weed-free crops are critical to successful sugar beet growing.

In recent seasons we have lost some very effective actives in sugar beet. Chloridazon was a very cost-effective residual component of many weed control programmes and was the pre-em choice of many growers and agronomists. Desmedipham has been around for several years and was a major component of many of our best contact materials and that was lost in 2020.

Other products are under review and that, combined with restrictions in use in terms of maximum amount of active ingredient per season and reduced doses of those that remain, has meant that weed control has become more expensive and more challenging.

Tractor hoeing is starting to become popular once more and the development of modern robotic hoes may well have a significant role to play in the future.

Conviso Beet

One piece of modern technology that is available now is Conviso Beet.

Conviso beet are herbicide-tolerant beet that have come about with a collaboration between Bayer and KWS. Conviso beet were launched into the UK in 2019 and have shown to be a robust technology adopted by many growers, giving excellent weed control with simpler management and fewer sprayer passes.

Conviso One is the herbicide component and contains 50g/L foramsulfuron and 30 g/L thiencarbazone-methyl.

Conviso One controls most weeds, including volunteer potatoes, with the only significant gap being common field speedwell, not a particularly competitive weed in sugar beet. It will also control weed beet and that has been the target for use by some growers.

KSW has developed the varieties via a conventional breeding programme when one beet from many millions was found to be resistant to the herbicide by a natural genetic mutation and has developed modern sugar beet varieties from this.

As with all new technologies in sugar beet, there is a slight yield lag against conventional varieties on the Recommended List produced by BBRO each season. When the first BCN-resistant varieties were introduced, there was a yield lag but now many of the top-yielding varieties such as Daphna are also BCN tolerant.

What is not widely understood is that the BCN-resistant varieties in the Recommended List trials were grown in non BCN-infected fields, so that the true benefit was not always measured.

A similar thing happens with Conviso beet, where in the Recommended List trials they are grown under a conventional herbicide control programme, so the true value of their herbicide resistance is not really measured. Conventional sugar beet herbicide can have a phytotoxic effect on beet under certain conditions, as we know, and can reduce the yield potential, but the beneficial weed control effect of the herbicide vastly outweighs the negatives.

Conviso beet are not affected by the Conviso One herbicide, so there is not the potential for phytotoxicity, and the true value of the technology may not be realised to its full potential in the Recommended List trials.

Currently there are two varieties on the Recommended List for 2022- Smart Rixta KWS and Smart Janninka KWS. Smart Rixta is yielding 92.2 % of the adjusted tonnes of the control varieties but, with no potential for phytotoxicity from conventional herbicides, will perform better than this in many situations.

This could make the Conviso Technology a current and very Smart option for growers to exploit in 2022.

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