Oilseed Rape Choices Autumn 2012

It has been a long winter – or so it seems, but today at last, the first days of Spring have arrived! Woopee!

That said we need to start planning for the 2012 / 2013 campaign if only in getting together first ideas on varieties. I had the opportunity of attending one of the HGCA Oilseed Agronomy Workshops back in January and also had a long conversation with the soil-borne disease guru of oilseed rape – ADAS Peter Gladders yesterday specifically about verticilium wilt and thought I would share some real ‘nuggets’ of information with you.

Club Root

I’m sure you are all aware that once you have clubroot then your days growing oilseed rape have pretty much ended unless you grow resistant varieties.

Historically clubroot has been pretty much a Scottish issue, but more recently as a steady increase in the implementation of short rape rotations and the commodity value meaning more rape is being grown on poorer quality land (light and marginal land) then the disease has increasingly appeared in England too. Most recently clubroot has been found in the Midlands and now in North Norfolk. Equally the intense pressure we are now seeing as a result of close rotational cropping (rape one year in two or three relative to soil type and minimal tillage) has meant that resistant varieties are being exposed to a rapidly evolving disease pathogen which through mutation will ultimately overcome the ‘single-gene resistance’ of even the most recently introduced variety Cracker.

That said in the presence of clubroot and the wish to grow oilseed rape, Cracker remains your best option until its ‘multi-gene resistant relative reaches the market – and it’s not far away!. Perhaps more importantly in the interim other breeders will be highlighting the introduction of their latest ‘break-through’ in clubroot resistance, proclaiming – no doubt that they are superior to anything else on the market (I can be as cynical as the next man!). The likelihood however, will be that they carry exactly the same resistance gene as Cracker and so will be equally susceptible to any mutation of the current clubroot pathogen. 

It remains critical to the longevity of Cracker within the market (and indeed any other variety carrying a single-gene resistance to any disease)  that this variety is ONLY grown where the disease (in this instance clubroot) is already in existence. In Scotland  2011, Cracker out-yielded even conventional varieties and as such many farmers may have bought it and drilled it without clubroot being present (that is only conjecture on my part, but seems likely to me). They won’t be doing Cracker's resistance to clubroot any favours.

Anyone who has identified clubroot on their farm and has not as yet tried Cracker, please do ring me as I have stocks available for this autumn. With a light leaf spot score of ‘9’ It sits fully recommended on the HGCA RL for 2012/13 and is unsurpassed in its field.

Verticilium Wilt

As part of a continued assessment of Verticilium wilt (VW) in the UK and its current impact on oilseed rape yields, Peter Gladders ADAS has a trial site containing 34 varieties (relative to which breeders are funding the trial) at Hacconby in the Lincolnshire fen - a site that is heavily infected and was the first indication in the UK three years ago that VW could be devastating in oilseed rape. It is Hutchinson managed and purely funded by breeders. Peter’s ‘ brief’ is to bring awareness to the farming community to the potential severity of VW and to give impartial judgement on the disease etc. If you get an opportunity to visit the site I would recommend that you take it as unless you are on a 1 in 5 rape rotation, are on good deep-rooting land such as fen soils, with yield potential hitting 7 or 8 tonnes per hectare, there is the likelihood that VW will have an impact in some way on your land.

Note despite the potential damage VW could do to the national rape crop, funding is very poor and Peter can only afford one trial site per year. He told me yesterday of the reservations he has on the 2012 site -

1.      Lincolnshire fen as a location is not going to stress the crop too much, the roots will be sitting in moisture and fields have the ability to yield up to 8t/ha so verticilium wilt is unlikely to cause any serious measurable degree of yield loss even if present.
2.      The plots are under an intensive management regime by Hutchinsons so again, stressed plants are unlikely.

Peter Gladders is the first to admit that one trial a year is not enough to thoroughly monitor or research this disease as there are many unanswered questions and its possible that the Germans or French are further ahead in their research than we are – I hope to visit the German breeder responsible for Cracker, Thorin and the new-comer Avatar later this month so will ask the question.

Points mentioned in our conversation:
1.      Excalibur is a major problem. It 'bulks up' the disease quicker than any other variety. As the most widely grown variety nationally, the likelihood that it is harbouring the pathogen to further infect neighbouring crops seems most likely, Castille isn’t much better, but is less grown these days.
2.      The strain of verticilium wilt appears to be a hybrid, originating from a broad spectrum form to one specific to crucifers. That said while it is hosted predominantly by brassicas there is evidence to suggest that it may be harboured by mayweed and even possibly wheat!
3.      Verticilium presence tends to be an expression of plant stress so where no stress exists the pathogen is unlikely to do much harm - hence the issues Peter has with the Hacconby site this year.
4.      There is often other problems before VW finishes off the plant. Castille for example was severely affected by it last year, but on further examination the variety had been suffering with a major stem canker infection initially.
5.      It's easy to find extremes of the disease in a stressful year, but many of the big hybrid and big canopy varieties can withstand its presence – PR46W21 in particular, DK Cabernet and Sesame.

Considering the above there is clearly a question mark over point 1. How come if Excalibur is a major carrier did it clearly perform so well on grower’s farms last year? I guess it’s a warning note that we would be foolish not to register. If you are on a short rotation, minimal cultivate or marginal rape-growing land, don’t over-do the Excalibur area, or place your Excalibur crop well away from your other rape. The other thought may be that Excalibur’s earliness to harvest means that it has produced its seed and oils before the WV can cause major damage. If the latter is the case then this is excellent news for AVATAR which is an ‘early to harvest’ variety too. But if that were the only varietal issue, then Cabernet and Sesame should be far worse than Excalibur for reduced yield effect in the presence of VW and this is not the case!

The other ‘nugget’ of information to me is that there is some negative correlation to wheat.

In the short term the warning is clear –  avoid any highly susceptible variety (Excalibur principally) in a short rotation situation in the presence of wheat (wheat/rape/wheat or wheat, wheat, rape, wheat). If on a min-till situation review your pre-cultivation techniques for more marginal soils, perhaps reintroducing ploughing. View Peter Gladder's HGCA presentation http://www.hgca.com/content.output/5997/5997/Events/Past%20Event%20Papers/Agronomy%20Workshop%20Newmarket.mspx

It would appear as with many soil-borne diseases there are many factors that interact to impact on yield loss and the mere presence of one or two of those factors does not necessarily mean that even in the presence of the disease yield will be affected. That said if by variety selection and careful field matching incidence of the disease can be reduced without impacting on potential yield then that has to be the way forward.

I have access to most rape varieties for sale this autumn and as with Thorin semi dwarf last year I have personal responsibility for a number of AVATAR trial crops situated around the UK. You can watch AVATAR develop yourself at www.watchitgrow.co.uk The breeder is having a few teething troubles up-loading the latest pictures but it will be sorted soon. Please feel free to contact me for a chat at your convenience. I hope to meet many current and new members in the course of the spring summer when we can review your particular situation. Any feedback you can offer from your own experiences or observations I would be delighted to receive.

Contact me by email at info@farming4profit.co.uk

Stuart Cree