26th May 2021

Keeping on top of Clubroot threat


Widening rotations and choosing club root resistant oilseed rape varieties are key strategies being taken to reduce the threat of club root at Dunecht Home Farms, Aberdeenshire.

Just over 550ha of the 1000ha farm is dedicated to arable crops, 30ha is rented out for seed potatoes and there are 100 cows and 2200 ewes at the low-ground farm.

Farm Manager Chris Lovie says: “Although we are a mixed farm, before I started working here two years ago, they used to run a tight arable rotation, with lots of brassicas for grazing sheep through the winter. This led to incidences of Clubroot, and we are now working to manage this threat.”

Clubroot is a major issue in rape in Scotland’s arable rotations, with over 50% of fields used for oilseed rape carrying the disease – and in areas like Aberdeenshire, the incidence is higher with the majority of fields affected.

Yield losses on average are around a third of a tonne for every 10% disease severity, but in severe early infections in warm autumns emergence can be so poor that crops are ploughed back in so, at the extreme end, yield losses can be 100%.

If a field is infected then drilling a variety listed as clubroot resistant is still the primary means of reducing the risk of yield loss.

Planning rotations is also really important to keep fields profitable for the long term. Even stretching oilseed rape rotations out in infected fields from three, out to five years is enough to make a difference to infection levels and reduce pressure on the varietal resistance mechanism.

Chris Lovie, Farm Manager at Dunecht Home Farms

In Mr Lovie’s approach to tackling Clubroot at Dunecht the rotation is being widened to include a minimum of spring and winter barley, wheat and oilseed rape in the rotation. This will help to ensure that rape is not grown more frequently than one in eight years.

He always looks to grow a Clubroot resistant variety, but notes it also has to be suitable for the more challenging winter conditions of Aberdeenshire.

“Being so far north, the cold can set in quite early on, so we look for good autumn vigour and we like a variety that is able to put on enough biomass.”

He aims to create the best possible seedbeds to get the crop up and away as soon as possible. “Ploughing is useful for creating tilth for an even seed bed on what are often very wet soils, and also helps keep slugs under control.”

He is also evaluating shallow and direct drilling using a Simba Horsch drill.

Drilling usually starts in August, with the rape often going in after winter barley, or spring barley if he can combine it early enough.

His plans for next year are to grow the exciting, new Limagrain variety LG Anarion, which is the first to offer effective Clubroot resistance, along with TuYV and pod shatter resistance, without compromising yields.

In Limagrain trials, LG Anarion showed an 11% yield increase over its current clubroot variety, Alasco, and 5% over other leading club root varieties; representing a significant improvement and further closing of the yield gap associated with Clubroot resistance.

“LG Anarion has very strong autumn dynamic growth with fast biomass accumulation and then sits in the winter, so it does not get too ahead of itself. It exhibits very good winter hardiness,” says Mr Lovie.

Agronomically there is much to like about the variety; it offers good disease resistance with breeders data suggesting ratings of 6 for light leaf spot, 6+ for phoma and a good tolerance to verticillium.

Mr Lovie also likes LG Anarion because it has early-mid flowering and maturity, as he finds that the longer oilseed rape flowers for, the better it performs. It also has good ratings for stem stiffness and lodging.

Moving on to talk about other cultural controls he is undertaking to reduce the incidence of Clubroot, he reveals that although some of the soils on the farm are loamy, they are generally not the most fertile.

“We are working to improve this so we are taking remedial activity with applications of cattle and sheep muck, plus the occasional pig muck.

“We are also trying to improve the organic matter content by adding digestate.”

He notes that low soil pH is often associated with Clubroot, so he is keeping an eye on acidity, and current pH is 6.2.

“We soil sample every 5 years and apply calcium lime variably.”

While N, P and K are applied at planting, Mr Lovie has moved to using a liquid fertiliser strategy with two applications in spring; one in early March and the other just before flowering to keep the crop flowering.

Mr Lovie says: “At the other end of the growing season, we direct cut it, so good pod shatter resistance is increasingly important to protect yields, especially as we often find that harvest gets divided into two parts.”

“As a way of getting there, we have found that LG Anarion ticks all the boxes for us agronomically while also offering really good yields.”

Charlie Catto, Agronomist for Agrii

Charlie Catto of Agrii, agronomist for Dunecht Home Farms, is looking forward to having LG Anarion available for his customers from next year.

“When it comes to oilseed rape, the faster it establishes the better chance it stands, so what is really appealing about LG Anarion is its ability to get out the blocks promptly,” says Mr Catto.

“The high autumn vigour, will help it to grow away from any potential flea beetle and slug damage.”

Fast establishment can be particularly important when it comes to a practical fit into the rotation, he adds, explaining that, if oilseed rape follows spring barley it is drilled a bit later than he would ideally like, so being able to establish well before the cold weather sets in, is a really important characteristic.

He is also pleased to see LG Anarion has pod shatter resistance, as this is high on his list of important traits for any new variety, noting that when windy at harvest this can make a difference to the yield of as much as 1t/ha in direct cutting situations.

“I really like the agronomic profile of the variety because it has resistance to the important pests and diseases, without taking a hit on yield.”

“For example, although turnip yellows (TuYV) is not yet much of a problem in this part of Scotland, by having resistance, growers know that they will not lose yield from this pathogen if it does become more prevalent.”

“As an agronomist, it is useful to find a Clubroot variety that has good light leaf spot and Phoma resistance ratings. We saw high levels of light leaf spot this winter in Aberdeenshire, so together with a good fungicide strategy, it will provide growers with effective crop protection.

“When these agronomic characteristics are added to yield and oil content – a high yielding Clubroot resistant oilseed rape variety supported by a robust agronomic package – it’s clear that LG Anarion is an excellent choice for the farmer’s gross margin.”

“Where we have issues with clubroot it certainly ticks all the boxes I’m looking for and will be my first choice this Autumn.”

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