Significant levels of verticillium wilt have been detected on oilseed rape varieties at trial sites in Suffolk and Sussex.
Run by the Association of Independent Crop Consultants (AICC), infection scores from the trials show different resistance levels between varieties, while varying yield levels demonstrate that performance impact is complicated.
AICC agronomist Peter Cowlrick of CCC, who managed the trials, said 2016 has been a high pressure year with the trial confirming what many growers are reporting on their farms.
“The season has generally been less than favourable to oilseed rape. Many crops went in late and in to wet and compacted seedbeds, while the mild winter did nothing to arrest disease development.
“It is under such situations when we tend to see the most obvious effects of verticillium wilt.
“It makes the plant less physiologically robust. It places the plant under duress, to the extent that it is less able to cope with the infection to the point that the infection is able to physiologically override the crop.”
The 2015 season also favoured verticillium wilt with yield reductions of up to 20% recorded. Along with this season’s results the AICC said it now has sufficiently robust data to inform its members concerning variety selection.
“For some time we have cautioned against choosing varieties which have been found to display more than 30% infection in the weeks before harvest. Of the 30 varieties in trial this season, 13 were found to be displaying infection above this level.”
The variety with the lowest level of infection was Barbados, a KWS variety added to the North Recommended List this year, with less than 10% infection. The variety with the highest level of infection was also a KWS variety, Quartz, added to the Recommended List in 2013, with an infection level of almost 70%.
“Barbados showed strong resistance and was among the higher yielding varieties. Flamingo at 4.95t/ha also looks promising while Incentive at 5t/ha performed admirably. We still have much to learn about this disease, but it is clear that when conditions suit, it is a disease that’s impact can be severe,” said Mr Cowlrick.