Rape under threat again as virus returns

INITIAL results from a survey of oilseed crops indicate autumn drillings are again at high risk of turnip yellows virus (TuYV) infection.

So far, samples from 32 survey sites have been virus tested by Broom’s Barn. Results of the Bayer CropScience survey indicate that the region has some of the country’s highest levels of infection.

At the majority of sites sampled, crops had 21% or more plants infected. But high levels of TuYV infection were found in unprotected OSR crops in Essex, Lincolnshire, Humberside and North Yorkshire.

Six sites had very high infection levels of 81-100%. These were located in Cambridgeshire, Essex, Kent, Hampshire, Glamorgan and Worcestershire. Only five sites have 20 per cent infection or less and just one is virus free.

Adrian Cottey, Bayer CropScience’s campaign manager for seed protection said survey results to the end of May were in line with those of the current HGCA monitoring programme.

“It’s becoming clear that TuYV is a widespread and every year issue for OSR crops,” he says. Infection risk for this autumn’s sowings would depend on the extent of peach-potato activity from here on.

While the Rothamsted Insect Survey’s predictions of first trap catches in England were mostly for mid-June, which was relatively late, numbers could build up rapidly, as seen during last year’s warm, dry June.

“Given the high level of infection in this year’s crops, the risk to autumn 2010 sowings is therefore potentially as high as last year,” said Mr Cottey . Trials by Broom’s Barn showed that TuYV could reduce yields by as much as 30%.

The only way to mitigate its impact on yield and oil content was to use an appropriate seed treatment. Modesto (clothianidin + beta-cyfluthrin) was the only option with a label recommendation for control of the aphid vectors of TuYV.

“Across 21 trials it has increased yield by an average of 0.34t/ha with an impressive top yield benefit of over 0.8t/ha,” said Mr Cottey.