Aphid âbarrierâ could help beat virus yellows
Aphid âbarrier could help beat virus yellows
by Arable Farming August 2020
As crop pests and extreme weather put sugar beet under pressure, BBROs 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 , 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 but we have seen positive results in terms of crop advancement through the season.
Biostimulants failing to deliver consistent response in beet
Recent research at BBRO has looked at applying biostimulants to healthy beet crops in a three-year trial over a range of soil types.
Knowledge exchange lead Dr Simon Bowen explained: We have failed to see any consistency of response in any of the products used where crops are healthy and do not believe there is any value in applying them some have a high cost attached.
What we have not looked at is applying them where crops are stressed and suffering from other pests or diseases and need helping along. We are going to look at how we can apply different levels of nutrients some biostimulants, macro and micronutrients to see whether there is value in applying some of the products in a more stressful situation.
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 BBROs 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?
Exploring genetic drought tolerance
Water use efficiency (WUE) is becoming increasingly important in the world of crop production and identifying varietal traits that confer more efficient use of water could help combat WUE.
This was according to Georgina Barratt, a PhD student at the University of Nottingham, who is exploring whether there are genetic traits that make certain sugar beet plants use water more efficiently.
During her studies she exposed two sugar beet varieties, one with an upright canopy and one with a prostrate canopy, to different irrigation regimes to determine how they used water, changed under stress and recovered from drought.
Speaking at the online event, she said: We found there were differences in WUE of the plants and the prostrate variety was more water use efficient and had a different carbon-13 value to the upright variety.
This is really exciting because these are commercial varieties. To find a difference that far through the breeding process means there is good potential there to make a more water use efficient variety.
We found in this scenario the prostrate variety, which had fleshier leaves and a lower stomatal density, so fewer pores to lose water from, was more water use efficient.
Ms Barratts work follows previous studies, which explored drought tolerance where different varieties were grown to determine the proportion of yield under irrigation that could be achieved under drought conditions