Dekalb trials manager, Anders Christensen reports on early OSR development across the country from the company’s network of 25 trial sites.
Solid Start Sets Substantial Potential
Winter oilseed rape establishment on our commercial farm trial sites from Taunton in the southwest to Dundee in the northeast has been noticeably better than last season. It has also been particularly consistent across their wide range of soil types and establishment regimes. What a difference a decent amount of soil moisture at drilling makes.
There were more than enough flea beetles about in the autumn and these were definitely more troublesome than they’ve been in the past for a number of northern and western crops. Thankfully, though, the pest pressure seems to have fallen back somewhat in the original hotspots of Cambridge, Buckinghamshire and Bedfordshire.
Generally good August and early September drilling conditions meant all our trial crops – with the exception of one in Lincolnshire where the mid-August seedbed became too dry – were able to grow away from the adult beetle attack well. Interestingly, even though we lost the trial itself here, the surrounding crop drilled only three days earlier into adequate moisture survived the storm. It just shows what a fine margin there can be between establishment success and failure these days.
An average plant vigour score of comfortably over 5 on our 1-9 scale 4-6 weeks after drilling across our main sites underlines the successful establishment achieved in all but the most challenging circumstances. What’s more, we’ve seen little, if any, establishment differences between our earliest sown trial on August 9 and our latest one on September 10.
Alongside DK Extrovert, DK Expedient, DK Exclaim and DK Expansion, notably vigorous establishment has been evident with our Clearfield varieties – especially DK Impressario CL. They’re showing themselves to be every bit as strong as our mainline varieties, getting extra benefit from their tolerance to any SU residues from previous cereal crops perhaps?
Development before winter ratings have also been encouragingly good, with most varieties scoring 6 or more on our 1-9 scale. Amongst our emerging varieties, DK Expedient and DK Impressario CL are joining DK Extrovert as some of the most rapid developers.
Slugs have been quite problematic on heavier ground which went into the winter decidedly wet; frosts have disposed of significant amounts of lower leaf; and pigeon damage has picked-up recently in many areas. However, most crops have been big enough and well-enough established to take these inevitable losses in their stride.
Coming into February, crops further south – especially the earliest sown ones – are clearly ahead of those in the north. Our first mid-January assessments, for instance, show an average Green Area Index of 1.75 across varieties on one southern site compared with
1.30 on two northern sites, despite these being sown two weeks earlier.
Having said that, we have populations well within our target of 25-30 plants/m2 across most sites, with a remarkable consistency between varieties and sowing dates. So it looks like we’re well set-up to produce some highly efficient canopies this time around.
As stem extension begins to become evident at our earliest sown southern site – although it’s still a good way off further north – we’re also going into the spring with some noticeably clean crops.
With the double phoma resistance we have in our mainline Ex varieties, it isn’t surprising we continue to experience extremely low infection levels in our trials – only having sufficient disease to be able to score varieties for phoma at just four sites.
Assessments here have, however, highlighted clear differences between the likes of
DK Expansion, DK Expedient, DK Exclaim, DK Extrovert and DK Exalte on the one hand and the key non-DK hybrids and pure lines we include for comparison.
We’ve yet to see any light leaf spot to date – even on our northern sites – but expect regional and variety differences to become increasingly obvious here as the season progresses.
Despite the wet autumn with very limited spraying opportunities in many cases, weed control has been reasonable across most of our sites. Volunteer sugar beet has been a problem in one case, but a timely dose of Astrokerb as part of the grassweed control programme seems to have done the trick here.
Rapid Development Limits Pest Damage
A recent study in our trial programme has shown that varieties with more rapid autumn and early winter leaf growth are better able to tolerate larval feeding from the early winter as well as adult flea beetle damage at establishment.
Our monitoring of a badly flea beetle-hit site revealed these varieties were as infested with larvae as others alongside them. But, assisted by a greater branching ability, their extra biomass enabled them to cope more effectively with the damage caused.
Overall, they lost markedly fewer main stems and suffered noticeably less stunting from flea beetle larvae than those developing less rapidly. They also tended to be better branched at flowering.
At the same time, main stem losses and stunting tended to be lower in varieties moving into stem elongation earlier after the winter than in those taking-off less rapidly.
In addition to their role in reducing flea beetle damage, of course, rapid development before winter and early stem elongation after winter allows varieties to better tolerate both slug and pigeon attack.