Oilseed rape growers should look to try out one or two new varieties each year to see how their growth characteristics perform on their own farms, advocates Mark Nightingale.
While the Recommended Lists provide useful guidance to relative performance, OSR variety breeder Mark Nightingale, of Elsoms Seeds, said farm location, soil type and agronomy practices – such as sowing date, establishment system and nutrition, for example – typically had a far greater influence on how a specific variety will perform, and its consistent reliability on-farm.
Speaking at the latest Syngenta iOSR grower group, on Sutton Estates’ Berkshire farm, managed by Joe Dilibero, Mr Nightingale said new genetic introductions could help growers to address some agronomic challenges of diseases and pests, but would only be of real value if the variety fitted the farm’s growing system.
“There’s no doubt different varieties offer distinctly different growth characteristics, for example. While some show the much acclaimed seedling vigour, that’s really just getting it up and out of the ground, but that might not translate into fast growth through autumn. “Growers have to decide what they want.
For most fast establishment is ideal as that can help to overcome flea beetle damage, but depending on your pest pressure, soil conditions, sowing date and climate, growers might not want crops too far forward in autumn and subject to winter frost dieback.
“It might be favourable to keep crops low and prostate with good ground cover over winter, and then see the vigour kick-in early in spring for strong growth and early flowering.” Mr Nightingale said vigour and growth characteristics were typically equally applicable to both hybrid and conventional varieties, with the company’s new open-pollinated Elgar giving the highest yield performance, early maturity and ease of harvesting which is ideal for UK conditions.
For iOSR host Joe Dilibero all the farm’s 125 hectares of OSR this year is Exalte, primarily due to previous reliability and disease resistance.
“Vigorous early growth has been good to get away from flea beetle damage,” he reported. “We did see some early signs, but was largely able to outgrow the damage, especially on fields which received a dose of chicken manure.
We only needed one flea beetle spray in autumn.” Mr Dilibero added the disease pressure had also been relatively low this year too, with just one spray for phoma in autumn and little or no light leaf spot symptoms. The crop did receive a midflowering sclerotinia spray, but again planning for just one spray treatment.
Northamptonshire farmer and contractor Greg Wilcox believed he had seen the effects of clubroot beginning to show up in the Midlands. Although most incidences were isolated patchy outbreaks, it has been spreading and there is increasing interest among growers for resistant variety solutions.
Syngenta oilseed rape variety manager James Taylor-Alford highlighted the new SY Alibaba has strong clubroot resistance and is the first in a potentially strong pipeline of the company’s clubroot varieties. “Clubroot is an increasing issue in OSR and is widely found throughout the UK, although is still most prevalent in Scotland and western regions,” he said.
“Depending on the extent and severity of infection, crop yield can be severely restricted.” Mr Taylor-Alford said lengthening OSR rotations, increasing soil pH and calcium content and growing a clubroot-resistant variety could help to reduce infection severity. “SY Alibaba is resistant to the P1 and P3 clubroot pathotypes.
In trials it also has good phoma resistance.” In Scottish trials SY Alibaba had proved more than twice as effective at reducing clubroot effects compared to the variety Mentor and, across all comparative European trials, had out yielded Mentor by 0.4 tonnes/ha.
Variety resistance had been offered as an option to reduce damaging incidence of TuYV in OSR, suggested Syngenta insecticides field technical manager Max Newbert.
However, while the genetic technology was good, in practice, the yield penalty of commercially available varieties tended to be greater than the effects of infection. “Unusually for plant viruses, TuYV exists within the leaf phloem, which inhibits the plant’s ability for natural immunity to the virus,” he explained to the iOSR growers.
“That means you still get yield debilitating infections after the four-leaf stage and all through winter. “Late flights of aphids, such as we have experienced in recent autumns through to October or November, still have potential to transmit infection.”
Syngenta testing in 2016 suggested 60-70% of OSR plants tested were infected with TuYV, making plants more susceptible to other stresses and contributing to yield losses in excess of 30%.
With the high level of pyrethroid resistance among aphid populations of Myzus periscae, which is the primary vector of TuYV, Mr Newbert advocated growers control initial migrations of aphids with Plenum to stop feeding and transmission of infection. Isolating foci of infection in the field can minimise its widespread effects.