Sugar beet growers are being urged to inspect their fields for signs of rhizomania – even if they grow resistant varieties.
Many fields in Norfolk and Suffolk are showing symptoms of the disease which was encouraged by the wet August, says Broom’s Barn virologist Mark Stevens. But he is concerned that relatively few growers have not had suspect beet tested.
“This, on its own, wouldn’t be a worry if they’d been taking notice and switching to resistant varieties for their seed order next year,” he says. “But only about 40% of the total order is for rhizomania resistant varieties.
“More worryingly in last season three fields were identified where rhizomania resistant varieties showed strong symptoms of the disease.”
Recent studies have shown the virus isolated from these beet to be genetically slightly different. The change was in a region of the genome thought to have given rise to problems in the USA, Spain and France, explains Dr Stevens.
“We need to get a good idea of the variation in the virus so we can better understand the potential development of resistance breaking strains. So I urge growers and advisers to check their fields and send in samples.
“The initial tests will be for the virus and, if it’s found, whether it is the more virulent P type or not, and then further tests to determine the genetic structure of the virus.”
He is keen to get as many samples as possible from a range of locations for these secondary tests.
“Growers should check fields sown with resistant varieties in case the disease is overcoming the resistance. If it is we definitely wish to know about it.”
Rhizomania can slash sugar contents – in 2007 from 18% to just 14%, he notes. “And if susceptible varieties are grown, the virus can spread rapidly through the field.”
The virus tends to be concentrated in the lateral root ends, so samples should be dug rather than pulled, advises Dr Stevens. Five topped roots should be sent double wrapped in sturdy polythene bags to BB Research Centre at Higham, Suffolk IP28 6NP.