Beet growers reveal the massive yield cost of virus yellows

A combination of virus yellows infections and poor growing conditions in the spring have devastated sugar beet yields for some growers, particularly in the Wissington factory region.

David Hoyles, who grows 60ha of sugar beet alongside potatoes, vining peas, wheat and a range of other crops, near Long Sutton saw a 70% yield drop from the first 38ha of the crop, which was lifted in late October.

See also: How the new sugar beet contract shares virus yellows risk

“Our five-year average is 92.2t/ha at 17.4% sugar content. This year we’ve lifted 28.8t/ha at 14.2% sugar from crops drilled in late March on more bodied silt.”

A very dry spring and late, uneven emergence didn’t help the crop, but he suggests 80-90% of the yield drop is due to virus yellows infection.

“It was the perfect storm – there were four or five aphids on every emerged plant in the first week of its life.”

beet with yellow virus

© Blackthorn Arable

About two-thirds of the crop turned yellow later in the season with virus yellows infection, despite an insecticide spray, he adds. “Ultimately I think it will have cost us twice as much to grow as we will get back.”

That calls the future viability of the crop into question, he admits. “I have signed next year’s contract, but with a very large reduction in tonnage. I am wondering whether to grow any at all. We have other rotation options; others are not so fortunate.”

This is the second season sugar beet growers have grown the crop without the aid of neonicotinoid seed treatments, which provided protection against the myzus persicae (peach potato aphid) which transmit the virus for around 10-12 weeks from planting.

Migration

Aphids began migrating from the third week of March, coinciding with beet drilling, following a mild winter with very few frosts, with populations building rapidly during April and May to virtually unprecedented levels.

With dry weather also holding back growth it was ideal conditions for high levels of infection, despite many growers following advice to use multiple foliar insecticide sprays as thresholds were breached.

Other growers in the Wash region in South Lincolnshire have reported similarly desperate yields.

Mike Neaverson, who also farms near Long Sutton, says the first lifted field on his neighbour’s farm, where he provides agronomy advice, yielded in the 40s t/ha on a farm where the five-year average is in the 80s t/ha.

“I would have expected on that field historically, given the difficult spring, an early lifted crop to have done high 60s to mid 70s t/ha, so we’ve lost around 40-50%.”

He also puts the drop primarily down to virus yellows. “We’ve had dry spells and difficult springs before and sugar beet has yielded very consistently. The field was bright yellow and all our beet fields had either three or four insecticides. But we are the aphid capital of the country.”

He also questions the future of the crop in the area, even with the new virus yellows assurance scheme announced by British Sugar in the 2021 contract. “If you plug the numbers from this year into that scheme, it’s still not viable.”

Reduce virus sources ahead of next year’s crop

The British Beet Research Organisation (BBRO) is advising growers to follow five basic farm hygiene guidelines this winter to help reduce sources of virus over the winter period.

  • Minimise harvester losses to reduce potential sources of regrowth
  • Monitor spoil heaps and destroy any growth
  • Revisit fields regularly and eliminate groundkeepers
  • Stop aphids green-bridging the virus by destroying winter cover crops at least five weeks before drilling
  • Control crop volunteers and virus-hosting weeds with well-timed herbicides and cultivations

Other areas

Other beet growing regions have been affected, albeit not quite to the same level as South Lincolnshire.

The first lifted field at Andrew Ward’s farm, near Leadenham in Lincolnshire, achieved 61t/ha at 16.2% sugar.

“I thought that was bad until I saw the reports of yields in South Lincs. Last year we did 94t/ha at 17.4%. We’re not going to break even at that yield. The galling thing is by spraying three times I have killed more insects than ever before at a time when we are trying to keep them.”

On the North Norfolk coast, NFU Sugar Board member Kit Papworth at LF Papworth Farms, Felmingham, says the first lifted field was later than usual and below 70t/ha compared with a usual average of 75-80t/ha on lighter land.

Virus yellows was much less of an issue, with yields hit by the extremely dry period from the second week of March to early June.

“We’ve not had the virus pressure that growers in the Wissington factory area have and whose yields are awful as a result. But the beet were flat on the floor for such a long time in that dry spell, and our yields are well below budget.”

The overall picture for sugar beet growers is one where many will be thinking the risk-reward ratio isn’t good enough, he adds.

“You’ve got professional growers on good silt soils thinking about not growing the crop next year because they can’t rely on it, and it’s not the only challenge sugar beet faces at the moment, with a difficult market.”

Biological control solution pilot shows potential promise

An innovative biological control solution visually reduced virus levels in a split-field comparison, although there is much to learn about how to use it most effectively both technically and economically, says Ely sugar beet grower Tom Clarke.

Working with biological control specialists Bioline AgroSciences, one-half of the 14ha beet field, which was drilled mid-to-late April, was treated with conventional insecticides, while the other half the biological control.

Lacewing larva

© Science Photo Library

Lacewing larvae
The biological control side was sub-divided further with half receiving primarily lacewing larvae up to the £50-70/ha cost of the insecticide programme, with the other half a recommended programme from Bioline, which had about four times the number of lacewing larvae and also included a parasitic wasp species.

The biological control was hand spread across the field by Mr Clarke on 10 June, which he admits was a little late.

“We already had a lot of ladybirds active in the crop and the aphids had largely been predated already, so we were a bit late introducing the predators to the crop.”

But he says there was noticeably less virus in the field where there were beneficials compared to the one he sprayed, and noticeably more naturally occurring predators, such as ladybirds and hoverflies in the unsprayed part of the field, with the least virus where he had applied the most beneficials.

That didn’t translate to any noticeable difference in yield – the field did 50t/ha at 16% sugar content, he says. “We weren’t in a position to measure it perfectly, it was more a look-see this year.”

Next spring
The results had enough promise for Mr Clarke to continue with the trials next spring.

“We’re going to take a slightly different approach. We’ll release the predators, but also feed the beneficials with sterilised moth eggs, which is how they produce them in the factory. The eggs are tiny protein packets for carnivorous insects.”

He is looking at ways that he can broadcast them in the field around drilling to get the beneficial predators in the field ready before the aphids arrive. “This hasn’t been done in the open before, so this is a new area.”

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