Concern over the area of oilseed rape grown remains with breeders taking steps to mitigate risks associated with growing the crop.
The decline began after a difficult 2012 harvest, exacerbated by the neonicotinoid ban in 2014, says Limagrain marketing director of arable seeds, Les Daubney. “It is at a low ebb. There is a lot of concern about oilseed rape. This season 530,000ha was drilled and 511,000ha is left in the ground.
“In the North there is more moisture and less cabbage stem flea beetle pressure. But areas of Essex are becoming a no-go area for oilseed rape.”
Seed cost is becoming more of an issue when establishment is unreliable, says Mr Daubney. “There has been a reversal in market share. Hybrids had the biggest share but now it is OPs [conventional varieties]. Hybrids are more expensive and if farmers think they are going to lose the crop it is a big risk.”
While clubroot has traditionally been associated with areas of Scotland, it is picking up in England, says Mr Daubney. “Given the amount of rape grown in the last 10-20 years and wheat/rape rotations we perhaps shouldn’t be surprised. Clubroot is in Germany now so there is more incentive to breed clubroot resistant varieties.”
Another traditionally Scottish disease moving south is light leaf spot which is more difficult to control than phoma, according to Mr Daubney. “Phoma is not spreading north but light leaf spot is spreading south. Growers are looking at light leaf spot resistance as a more important trait than phoma resistance as phoma is relatively easier to control.”
There are also signs that turnip yellows virus (TuYV) is becoming more widespread, according to Dr Vasilis Gegas, Limagrain senior OSR breeder, maritime. “There is a wide range of hosts – 120 plant families can be affected including brassicas and in Lincolnshire there are always brassicas in the ground. There can be as many as 20 generations of Myzus persicae in a season which increases the number of aphids infected.
“It is predicted that this year will be heavy for TuYV. The aphid count peaked in August/September and early infection hits yield more.”
The Rothamsted Research insect survey of cumulative levels of aphids for autumn/winter 2016 showed that more than 50 per cent of captured aphids were vectors and about 70 per cent in Lincolnshire, says Dr Gegas.
Symptoms of TuYV include purple leaves early in the season, early senescence of the canopy and severe infections can cause dwarfing. Infection can reduce seed yield by up to 30 per cent and oil content by up to 3 per cent, he adds.
However, erratic aphid movement makes timing of insecticide applications difficult. “It can be from July to November or December depending on the year.”
The first variety developed by Limagrain with TuYV resistance is Amalie which is now on the Recommended List and Architect, the first TuYV resistant hybrid is a candidate. TuYV resistant conventional variety Annalise is on the candidate list and has an improved yield over Amalie and a 46.9 per cent oil content, according to Mr Daubney.
The cause of high erucic acid levels in some oilseed rape crops remains unproven but concerns charlock could be implicated are driving demand for Clearfield varieties which are bred to be resistant to imazamox herbicides, says Mr Daubney.
Looking ahead, Mr Daubney says key characteristics of Limagrain varieties will include: gene-specific pod shatter tolerance in all hybrids, resistance to TuYV, high levels of light leaf spot resistance, a stem canker resistance score of greater than 8 in hybrids as standard, high early and spring vigour, and a high oil content.