Beet growers alerted to virus yellows threat in new season crop
Sugar beet growers are being alerted to the threat posed to crops by virus yellows infection in the coming season.
Teresa Rush
Following the UK Government’s decision in 2018 to extend restrictions on the use of neonicotinoid insecticides, sugar beet crops planted this spring will not be treated with neonicotinoid seed treatments thiomethoxam or clothianidin, which have provided effective control of virus-transmitting aphids since their introduction over two decades ago.
The virus yellows risk has been exacerbated by warm autumn and relatively mild winter temperatures to date, which have allowed aphids to survive in large numbers.
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Mild
“As we edge further into February aphids are overwintering on weeds and brassica crops, including winter oilseed rape. Although we have had several nights at -6degC to -8degC, we have not had a prolonged period of cold weather and really we could do with a ‘Beast from the East’ because otherwise there could be some quite serious consequences in terms of aphids,” British Beet Research Organisation (BBRO) lead scientist Dr Mark Stevens told a grower meeting in Newmarket, Suffolk.
Risk
In response to the heightened threat to beet crops an early virus yellows forecast was due to be issued by BBRO this week, with the full forecast due in early March.
“This will start to give you an idea of the risk we are facing,” said Dr Stevens.
Timing
In the coming season sugar beet growers will have only one chemical control option for aphids in the form of insecticide Teppeki (flonicamid), but with only one application permitted, timing will be critical.
“The problem is aphids may fly for up to 12 weeks and we have a product that will give, potentially, up to three weeks control. So you have got to get the timing right, hope you control the aphids and do not get many more re-entering the crop but the challenge we have is that after a mild winter this may not be the case.”
Close monitoring of crops will be essential in the coming season, advised Dr Stevens, who also urged growers not to try and control aphids using carbamate or pyrethroid insecticides because of problems with resistance to these compounds.
What can growers do to control aphids and virus yellows in 2019?
- Limit – destroy any cover crops which may be harbouring aphids ahead of sugar beet planting, practice good hygiene around cleaner/loader sites
- Monitor – follow BBRO aphid bulletins
- Count – count aphid numbers on10 sugar beet plants across the field
- Treat with Teppeki (flonicamid) at threshold – one green, wingless aphid per four plants up until the 12-leaf stage. Do not spray before the threshold is reached. Currently only one spray is permitted
- Keep monitoring
Source: BBRO
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