Fungal disease Verticillium wilt found on trial site crops in Suffolk and Sussex

Verticillium wilt in oilseed rape.

Verticillium wilt in oilseed rape. - Credit: submitted

A fungal disease which can affect a range of crops has been discovered on varieties growing at trial sites in Suffolk and Sussex.

The Association of Independent Crop Consultants (AICC) said the high disease pressure this year suited Verticillium wilt.

However, different resistance levels between varieties, and varying yield levels meant that the impact on performance was “complicated”.

AICC agronomist Peter Cowlrick of CCC Ltd, who managed the trials, said 2016 had undoubtedly 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,” he said.

Principal symptoms are grey striping on the plant stems, while maturity occurs several weeks earlier than normal on affected side branches. By harvest time the plant is clearly dead, while the stems of uninfected plants would still be green.

“In a low pressure season its effects are not always obvious,” said Mr Cowlrick. “The crop is able to tolerate infection when conditions are good and the plant has access to sufficient moisture and nutrients, but under stress, and we have seen plenty of that with light leaf spot and flea beetle, then the crop can suffer greatly.

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“My view of it is that 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 was a high Verticillium wilt year with yield reductions of up to 20% were recorded, providing the AICC with “robust” data.

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.

By coincidence, the variety with the highest level of infection was also a KWS variety, Quartz, added to the Recommended List in 2013, with an infection 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,” added Mr Cowlrick.