Troubled by static or falling oilseed rape yields? The problem could be turnip yellows virus, according to Mark Stevens of Broom’s Barn.

The virus, which was transmitted by Myzus persicae aphids in the autumn, didn’t express itself until late in the season, he warned.

“By the time you see the symptoms, it’s too late to do anything about it,” said Dr Stevens.

Preventing transmission

Yields could be reduced by 25% by the virus, he added. “We believe there’s widespread infection in the national crop. Almost 70% of the Myzus persicae aphids caught in traps are found to be carrying the virus.”

Bayer‘s new clothianidin-based seed treatment would help, although it was yet to be approved. “An effective seed treatment needs to give coverage through September, October and November, if it is going to prevent the transmission of the virus by aphids.”

Dr Stevens was hopeful that new research would help to develop spray threshold warnings based on a better understanding of the disease.

“It’s certainly one of the yield-limiting factors in oilseed rape. Looking around the plots at Cereals 2008, there were plenty of signs of the virus.”