Disease threat to oilseed rape crops

A potential disease threat to oilseed rape crops could spell major headaches for growers, a leading independent arable researcher has warned.Ben Freer, who is a senior agronomist with The Arable Group, said that club root poses a major potential threat to oilseed rape crops.

A potential disease threat to oilseed rape crops could spell major headaches for growers, a leading independent arable researcher has warned.

Ben Freer, who is a senior agronomist with The Arable Group, said that club root poses a major potential threat to oilseed rape crops.

Oilseed rape specialist Mr Freer, who was based at Morley, near Wymondham, for many years, said that farmers and growers could prevent the club root problem by following sensible agronomic strategies, management and avoiding too close rotations.

Although he had not seen cases in eastern England, he stressed that farmers should be aware of the possible consequences of club root for future crops.


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One expert, Barrie Florendine, who is a regional technical adviser with UAP, warned that it is becoming a real problem. In some cases, the worst affected fields are being written off.

He has seen more club root this season than at any time in the last five years. "We are not sure why, except that rotations are fairly tight, with rape now being grown one year in every three or four," he said.

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"Club root also tends to coincide where there is a history of brassica weeds such as charlock and it may be that these are hosting and retaining the fungus in the field.

"Infected plants have a poor root structure and can be ripped out at combining. As a result, cultivations will spread the fungus across the field and even from field to field.

"There's also the likelihood of contamination of seed in the combine tank from spores from galls disturbed at harvest. Thus, careless home-saving seed could also spread the problem."

He said that club root has been seen in crops in an area stretching from the Cotswolds to the Midlands, Yorkshire and into Scotland. It is being found in a range of soils from brash, clay loams to sandy loams.

Club root occurs across all brassica species, including turnips, kale, cabbage, cauliflower, broccoli and sprouts as well as oilseed rape. Cruciferous weeds such as charlock and shepherd's purse are also susceptible.

The fungus infects the plants roots, causing irregular swellings - 'galls' or 'clubs' - on the main root and often on laterals as well. As a result, plants are less able to take up water and nutrients and are lower yielding.

"The club root fungus - Plasmodiophora brassicae - can persist in the soil for 20 years or more. So, the implications are that the disease won't go away," said Mr Florendine.

He said that with yield losses of between 50 and 100pc for conventional varieties, the only option is to grow the club root resistant variety Mendel.

"While you will have to accept a 10pc yield reduction compared to other varieties, growers can make up this difference by getting the variety into the ground in good time and utilising it's hybrid vigour," he said.

Plant breeder, CPB Twyford said it is sourcing increased supplies of Mendel for next autumn, but warns that with club root now a significant problem in continental Europe, stocks could soon run out.

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