Top tips for a successful OSR spring restart

There will be no one-size-fits-all approach to oilseed rape management going into spring, with last autumn’s variable weather across the UK regions set to have a significant impact on crop establishment and over-winter survival.

Overall cabbage stem flea beetle numbers were lower last autumn, evidenced by data generated from a national network of Bayer’s newly launched MagicTrap digital yellow water traps but wet weather further north and a delayed harvest meant knock-on delays to oilseed rape drilling and compromised crop establishment.

However, with the oilseed rape crop area for harvest 2025 estimated to be down by 36% on 2024 at around 226,000 hectares, timely crop assessment and targeted management in the coming weeks could pay dividends this season.

In England, new season oilseed rape crops were planted in generally good conditions.

Bayer trials manager Richard Williams, responsible for Bayer’s nationwide Dekalb oilseed rape strip trials programme, says: “When I visited our strip trial at Rougham Estate, near Bury St Edmunds in Suffolk in December, it was up to my knees.

“It was drilled on August 7th and that’s what we have to do in the East; we have to get in with the drill early and hit the moisture early. That’s what the team at Rougham did and they have a fantastic crop.”

It was a similar situation across in Herefordshire, where plant counts in the strip trial ranged between 33-48 plants/m2 in December – nicely within the optimum range of 30-50 plants/m2.

“We know from our trials over several years now that a population of 25-40 plants/m2 is needed for the best performance. Some of these very well-established, thick crops are likely to benefit from a little thinning out overwinter or in some cases a spring PGR,” says Richard.

“A key message is that we are not seeing anything different in terms of establishment between DK Excentric, which we launched last year, compared to say tried and tested DK Exstar or our pipeline variety CWH 596, which are earlier varieties,” he adds.

Further north, the situation becomes a little more challenging. At the Borders strip trials site at Coldstream a severely delayed harvest saw the new season oilseed rape drilled into some of the wettest seedbeds in memory.

“When I walked over the trial there was nothing that really jumped out as an issue but, from a general agronomy perspective, it's just been under pressure from the off. It isn’t down to problems with slugs or flea beetle, it is purely down to a wet seedbed,” says Richard.

Up in Perth, Dekalb AHDB Recommended List candidate variety DMH 585 got off to a flying start, with a robust, uniform plant stand that will see it nicely through to early spring.

With plenty of phoma to be found and clubroot much more of a problem in the North, clubroot resistant DMH 585 will definitely be one to watch this season, says Richard. The variety also brings TuYV and pod shatter resistance and excellent phoma resistance.

“We want to see higher plant numbers up here as the winters are harder. There was nothing to pull DMH 585 apart from the other varieties in the strip trial in terms of vigour; its uniformity was phenomenal, and plant size was perfect – what I call ‘small plate size’ – for the time of year,” he says.

Bayer technical manager Ellie Borthwick-North urges growers to keep a close eye on crops and if necessary, manage them on a case-by-case basis.

Ellie says: “We know oilseed rape is still the best break crop ahead of a first wheat. As a crop it will come back into favour; we just need to have some patience and wait for the CSFB tolerant varieties to come through. They are starting to appear on the horizon, and we are getting good feedback from our breeders.

“But right now it’s about getting out and checking crops and making sure we look after them with good farming and good agronomy.”

Top tips for spring restart

• Cabbage stem flea beetle pressure was lower last autumn than in previous seasons; however, checking crops regularly for the presence of larvae is advised

• In some regions wet seedbeds have put crops under pressure from the outset. Assessment of plant population, rooting and CSFB larval presence, along with a realistic appraisal of the return on investment required can help inform decisions on a crop’s future

• January frosts have reduced the canopy size in bigger crops, but where larger canopies persist, crops may benefit from an early application of tebuconazole

• Consider delaying or reducing the first nitrogen split in well-established, forward crops but prioritise N on smaller, backward crops

• Light leaf spot symptoms are starting to appear. There is no treatment threshold – apply a fungicide such as Aviator Xpro (bixafen+prothioconazole) at the first signs of disease or as soon as field conditions allow