As featured in Arable Farming Magazine
Aphid ‘barrier’ could help beat virus yellows
by Arable Farming August 2020
As crop pests and extreme weather put sugar beet under pressure, BBRO’s BeetField20 Virtually Live online events provided growers with some pointers to adapting to the changing meteorological and political climate. Alice Dyer and Marianne Curtis report.
The potential for use of biodegradable polythene film as a tool in the fight against virus yellows is being examined by the British Beet Research Organisation
Stephen Aldis, crop production and mechanisation specialist at BBRO, explained to a BeetField20 Virtually Live webinar that the film could act as a physical barrier to aphids, deter them from landing on it because of its colour and enable crops to reach the 12-14 leaf growth stage where mature plant resistance kicks in.
“A demo strip at two sites indicates very clean crops where the film was used with beet elsewhere in the field showing virus symptoms. However, there is still time for symptom expression over the next few weeks [through July],” he said.
Work is continuing on developing the system.
Mr Aldis said: “We are looking at how we can set up the seedbed and adapt it to beet. Beet is different to maize [where film is already used] but we have seen positive results in terms of crop advancement through the season.
“We are looking at removal dates for film and how long to keep it on for maximum benefit. Because of the film, all N must be applied at drilling. There are a lot of technical challenges that need to be figured out and costed up.”
However, indications so far show there is enough of a yield lift to justify the cost, he says. The film costs £250 per hectare and all costs are £320/ha based on
work done so far.
Meanwhile, BBRO head of science Prof Mark Stevens explained the value of beneficial insects to combat infectious aphids.
Research in Europe has shown that flowering field margins have positive influences on beneficial insects such as hoverflies, ladybirds, spiders and ground beetles, which predate virus-spreading aphids.
However, they often only have zones of influence of about 10 metres, he said.
“Strips can work as a push or a pull for pests – you either try and increase the predators so they move into the crop or, if you get the right species, you can pull
aphids into certain specific areas by using brassica species. The aphids are more attracted to the brassicas than the sugar beet , preventing build-up in the sugar beet.”
An integrated approach combining beneficial insects, varietal tolerance and resistance and appropriate use of aphicides will be the best way to control virus yellows in the future, Prof Stevens said.
For other pests such as beet leaf miner, where growers historically relied on seed treatments and sprays, there are certain species which predate them, he added.
“Parasitic wasps, which we can potentially build up will have a key role in control in the future.”
Organic manures at variable rates
With sugar beet growers reporting uneven crops this year, Dr Bowen said work being done at BBRO’s Morley Farms site in Norfolk, where soil is being sampled at a high number of points in a field, is showing good and poor establishment quite strongly associated with soil organic matter content.
While average organic matter in the field is 3-3.5%, it can be as low as 2% and as high as 7%.
Dr Bowen said: “Better establishment is usually associated with high organic matter areas.
“So should we be considering variable rate organic matter application, targeting areas where we know organic matter is lower?”