Growing oilseed rape successfully is not a straightforward business these days, and, as Heather Briggs discovers, growers need to keep an open mind on a number of factors when it comes to variety selection for the 2019-planting season.
Oilseed rape variety choice should be based on oil content, ability to withstand pests and disease, stand up to weather and disease pressure, as well as having important characteristics such as stiff straw, according to Agrii seed technical manager David Leaper.
Cabbage stem flea beetle (CSFB) remains a major challenge for many oilseed rape growers, he notes.
Geographically the pest had a much wider impact last autumn, and may even force the decision to take a ‘holiday’ from growing rape this autumn, he says.
In other cases, the gut reaction of many growers is to drill early so the crop is already growing away when CSFB arrives, but then the beetle lays the eggs and the plants become infested with larvae.
Historical advice from Rothamsted Research was to drill after the CSFB migration has taken place but, as this generally happens from the end of August and can continue throughout September, it is impractical because establishment conditions often rapidly deteriorate during September.
Mr Leaper says: “The situation is far from straight forward and a number of techniques have been used to reduce the impact of the pest. These include companion cropping, the use of sacrifice areas, drilling into longer stubble and the use of varieties. All have some effect, but cannot be relied upon on their own.”
Work with Bayer on heavily infested crops in the Cambridgeshire area (Trumpington) looked to see if varieties with a fast speed of development in the autumn and early spring can grow away from the larvae.
“We found DK Expedient to produce a big strong plant with good roots and growing points in the rosette. Additionally its fast growth habit helped it cope better with the larvae than many others.”
Hybrids are becoming increasingly popular in UK because they show ‘heterosis’ or hybrid vigour often seen in the spring, even though there may not be big differences in yield. But, he cautions, hybrids cannot all be treated in the same way.
“You need to look at all the varieties in trials and assess their growth habit; generally we tend to prefer those that develop the fastest, such as DK Exalte, InV1035 and DK Expedient.”
In terms of Clearfield varieties, Mr Leaper again prefers those with fast autumn and spring development such as DK Impresario and DK Imperial. This is not only important for CSFB but also helps early competition against volunteers and problem weeds.
Resistance to turnip yellows virus (TuYV) is also of increasing importance, believes Mr Leaper.
“For many years we have applied foliar insecticides and the neonicotinoids to achieve reasonable control of the aphids which are vectors of the virus, but since the withdrawal of the latter, Limagrain has been leading the way in introducing resistant varieties.”
Although the virus is endemic across the entire UK oilseed rape acreage, it is difficult to spot as symptoms are often absent or very subtle and its impact is therefore often ignored. Agrii has worked with Limagrain portfolio manager, Vasilis Gegas, to identify virus levels in the plant through tissue testing.
Mr Leaper says: “The disease is measured by the percentage of plants infected in a crop. In 2017 we discovered high incidence across the UK, whereas in 2018 the infection was more moderate. We believe that 2019 may be another high year as the infection is closely related to aphid levels in the autumn which were widespread with the mild weather.
While most international breeders focus on hybrids, he notes that 50 per cent of the UK acreage is still in conventional varieties. Aspire is an important variety as it is the only conventional RL variety with the TuYV resistance trait and it is one of the reasons why it is the highest yielding variety on the list.
Clearfield varieties have recently taken a significant share of the market (20 per cent), driven initially by growers with problem weeds such as charlock and runch.
“The other key driver has been erucic acid contamination of crops which can result in rejection by the crusher. An AHDB study found that legacy volunteers from many years ago may be the source of this contamination. Clearfield is clearly one simple way to remove these volunteers from the growing crop.
Interestingly, he adds, the problem was only seen in the UK and there has been no erucic acid problem where Clearfield varieties were grown.
“However, removing contamination is one thing but not re-introducing it is another important consideration. Certified seed is already being screened for this, but growers using farm saved seed are strongly advised to get their seed tested.
Breeders have also been selecting for other genetic traits such as pod shatter resistance. Introduced initially by Dekalb more than a decade ago it has recently become mainstream with BASF, Limagrain and DSV offering it in their latest hybrids too.
Club root is still a significant disease in some areas exacerbated by acid soil conditions, localised flooding, and short rape rotations particularly where crops like stubble turnips or other brassica are grown.
“The are some interesting new varieties to help alleviate this problem, Alasco also from Limagrain, Crome from LSPB and Crocodile from DSV. It is important to note that they tolerate the disease and may still show some symptoms.”
Mr Leaper also draws attention to a part of the market that pays a premium for oil quality over the commodity ‘OO’ type and points out that High Oleic (HOLL) varieties still attract a minimum premium of £20/t for harvest 2020.
“V316OL remains the main HOLL variety and, in spite of it being in the market for six years, it is still the most profitable variety when you take the premium into account,” he says. “This year Bayer has introduced a new variety V353OL which has a similar yield but also a faster growth habit which helps offset CSFB.
“The breeders continue to bring innovation to oilseed rape through higher yields, better disease resistance and new genetic traits. They form a crucially important part of the overall agronomic package to minimise risk and maximise yield – and therefore profitability.”
The importance of vigour
Plant vigour plays a key role in getting oilseed rape established, says RAGT technical sales manager Dr Cathy Hooper.
However, choosing a variety with vigour can be difficult, as there are currently no vigour ratings on the Recommended List.
“When autumn weather is kind, it makes it much easier for oilseed rape to get up and away,” says Dr Hooper. “It is during difficult seasons that we really see the need for vigour.”
This uncertainty has led to RAGT entering into an innovative agreement with BIPO Ltd (Breeders’ Intellectual Property Office), which will see the breeder’s new OSR genetic material such as RGT Nizza CL, RGT Quizz and RGT Azurite entered through the well-established Royalty Area Collection scheme.
This means that growers who are forced to rip up failed crops could significantly reduce their losses because they will only have to pay royalties on the area of oilseed rape that establishes.
Growers place their order as normal, but need to collect an IC number from BIPO, explains Dr Hooper. “They simply declare the area of oilseed rape established by 1st November, on which they will pay royalty.”
Of the new varieties, she notes that RGT Nizza CL has good vigour, but growers in areas where LLS disease pressure is high will need to look after it.
“We have a very nice package with RGT Quizz, a low biomass variety which has multigenic resistance to phoma in addition to being tolerant to turnip yellows virus.”
RGT Azurite has higher biomass than RGT Quizz, but it combines good stiff straw with high autumn vigour.
“The combination of good vigour and reduced up-front seed costs for growers who sign up to the scheme will be a useful risk management option for growers, especially in areas prone to flea beetle attack.
“So far, feedback has been good, but we will have to wait and see how it works out.”
Using the RL
Sowing rates, pesticide application, fertiliser rates, establishment systems and soil type are all key variables affecting variety performance so the RL is a great way of allowing farmers to see how varieties perform in their region, says Elsoms Seeds’ combinable crop manager George Goodwin.
He believes winter oilseed rape will be an attractive option in 2019 and, as long as it establishes well, growers should be able to achieve good gross margins.
Mr Goodwin says: “Oilseed rape allows a good entry for the next cereal crop (relative to other crops) and offers growers an opportunity to over-winter a catch crop before spring cropping to help maintain soil health and structure.”
A successful innovator in seed technology and breeding research, Elsoms Seeds has two oilseed rape varieties, Elgar and Kielder.
Elgar is now in its fourth year on the RL, while Kielder, a newer addition, is a stand-out variety for growers from north Lincolnshire upwards with high resistance to light leaf spot and lodging.
“There will be good seed availability for both varieties this year,” says Mr Goodwin.