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‘A Perfect Storm’ – British Sugar Beet Review – Darryl Shailes

In what has been an unprecedented year for Virus Yellows. Darryl Shailes takes a look at how to optimise this season’s crop ...

Plus shares his thoughts on lifting strategies, and looks at the lessons to consider for 2021.

2020 has been a challenging season for sugar beet as difficult as many can remember. When the weather broke at the end of September and then continued to rain for most of the winter, we knew we could have a challenging spring. For that wet and mild winter to be followed by a very dry and cold early spring it was the worst of all conditions for establishing the sugar beet crop.

DARRYL SHAILES, ROOT CROP TECHNICAL MANAGER

The very difficult seedbeds that followed made good establishment almost impossible for any soils much heavier than a sandy loam.

Even the best silts in Lincolnshire were a challenge and the clays and mixed soils of Norfolk and Suffolk the same. The BYC winners have all had excellent establishment so we were already on the back foot.

The poorly-established crops and dry weather that ensued then made it a real challenge to keep fields weed free and many crops although having been sprayed more times than normal are still weedy with fat hen being the main issue. The work done at Brooms Barn in the last century, 1994, shows that fat hen population of 2 and 5 per m2 reduce yield by around 16% and 40% respectively so fat hen and other tall shading weeds are putting us further behind.

Then of course we’ve had record numbers of aphids in the crop and virus is showing up in most fields.

Interestingly it was also in 1994 that we had the first neonicotinoid seed dressing, so we need long memories to have seen such high levels of virus in a sugar beet crop. It was almost the ‘perfect storm’ for aphids and virus.

  • A mild winter so that Myzus could over-winter very well
  • Gappy crops making timing of the available products challenging
  • Huge numbers of aphids migrating into the crop much earlier than normal

The long-term average number of aphids caught in the traps at Brooms Barn by the end of June is around 460. In 2020 this was up to 4,400, nearly a ten-fold increase. When we consider that the threshold for treatment is one green wingless aphid per four plants, but some fields had counts of up to 100 aphids per plant when they were still very small, we knew we had a problem.

An almost impossible situation, even with the excellent chemistry we had available due to the work of BBRO, British Sugar and NFU Sugar in getting the Emergency Authorisations.

So, what lessons have we learnt and how can we optimise this season’s crop?

We must not let disease become an issue. The standard policy should be to use a full rate of a broad-spectrum fungicide as soon as disease is seen or better still reported in the locality. Other treatments then follow at 28-day intervals or when disease is seen to be re-invading the crop, with up to 3 or even 4 treatments depending on lifting dates and harvest intervals.

The winners of the BYC have all had strong fungicide programmes.

The big challenge will be if Cercospora, which seems to be increasing year-on-year, comes in early. Tests in the UK show Cercospora is resistant to Strobilurins, not as sensitive to triazoles as we would like and we don’t have the broad-spectrum contact materials available to us that some other countries do.

When I attended the IIRB (International Institute of Sugar Beet Research) conference in Brussels in February a large part was taken to breeding for Cercospora resistance and trying to understand the mechanisms of fungicide resistance by scientists across the world, where Cercospora is the main disease in sugar beet and many crops are sprayed 5 or 6 times.

So, we need to be on our guard and hope for more information from BBRO and breeders on Cercospora rating of sugar beet varieties going forward.

Nutrition is another factor we mustn’t let slip. Tissue analysis can help and trace elements can be added to fungicides in many instances providing they are compatible.

What about bio-stimulants? We’ve had some good results in our trials with statically significant yield increases, however BBRO haven’t seen this in theirs so we will put that to one side for now.

Lifting date?

Normally it would be based around variety, looking at the Recommended List for disease susceptibility, site selection, rotation etc. This season however its most likely to be those crops that are well established, have low virus levels and fewest weeds that have the most potential. Lift the fields with the least yield potential first and get another crop in and leave the best to last where possible.

So, what are the lessons for next season?

Establishment, is a big one. The fields that needed the most work this spring are the least well established. So, we must try to minimise the need for a lot of cultivations in the spring.

I’m not a believer in cover crops being the panacea for all ills, but this spring, crops that had a cover crop (even a poor one over-winter) and subsequently needed little work to make a seedbed this spring have, in the main, established better from what I’ve seen.

Ploughed land – due to the lack of frost or wet-dry wet-dry to weather the soil – has needed multiple cultivation to make any sort of seedbed, completely drying them out and trying to establish a crop in soil like very dry marbles has not been easy.

Making the seed bed in the autumn and using a cover crop to maintain the structure has paid off in many instances this season, much better than late ploughing and a wet mild winter anyway.

Weed management, with the loss of Desmedipham and the excellent formulations we have enjoyed over the last few years is likely to be more challenging. Agronomists and growers will need to be timelier with their advice and applications. We have one new technology CONVISO Smart from Bayer and KWS, and whilst not for every field will be a useful tool in the armoury.

And then virus, first of all hope for a long cold winter to reduce the numbers of over wintering Myzus persicae. The reduced area of oilseed rape may help as they provide overwintering sites.

Have good chemistry available and use it timely. Are there any varietal differences? It seems so from fields observations. Ensure we manage virus hosts in other crops, bolting crown in wheat etc.

Remember BCN, soil pest complex and lime testing too – easy to forget with all the issues of 2020.

And one last thing, this season, anecdotally, some fields with barley cover crops seem to have less virus.

Is this a masking effect not allowing the aphids to identify the beet?

Could we use other more attractive species in the beet and then manage with the CONVISO Smart system?

I don’t know, but something worth looking into.

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