The soil-borne oilseed rape disease, verticillium wilt, has been officially found in oilseed rape for the first time in the UK, David Slawson from DEFRA’s plant health unit says.

Two samples sent in from ADAS sites in Kent and Herefordshire were found to be infected with the fungus, Verticillium longosporum, following testing by the Central Science Laboratories in York.

The disease produces long, grey streaks on stems leading up to swathing time, and as such can easily be confused with phoma and sclerotinia, which also cause root and stem blackening, according to ADAS plant pathologist Peter Gladders.

“The difference from phoma is that these streaks can run for long distances – maybe up to 1m – while phoma symptoms tend to be only a few inches in length.”

The fungus invades the root system in the autumn, but usually remains symptomless until the spring, when it moves up through the plant’s vascular system once stem extension starts, he explains.

Verticillium infections in oilseed rape crops have been suspected for two or three years in the UK, but this is the first time the disease has been officially recorded, he says. “I thought it was important there was an official UK record.”

About 10-30% of plants were infected at the sites. “Quite a lot of the symptoms were on the lateral shoots.”

Yield losses from the disease are difficult to estimate, he suggests. “Researchers in Sweden, who have been battling with verticillium for 50 years, acknowledge it can be from very little to up to 50%. In these cases only the odd one senesced early so I suspect the damage was minimal.”

Control options are limited. “There’s not much else you can do other than extend rotations. It declines in soil over time, but observations in Germany suggest you need rotations of one in four or five years to reduce its impact.”