The effect of losing neonicotinoid chemistry has not been as bad as feared for four oilseed rape growers this autumn. Paul Spackman reports in the second of our series
Flea beetle not an issue
Doug Taylor, Kent
Good early crop establishment, combined with favourable weather and a two-spray insecticide programme, mean flea beetle has not been an issue on Doug Taylor’s 450ha farm near Folkestone.
Mr Taylor, who is growing 90ha of untreated Trinity, ES Alegra, Cabernet and Catana plus some Pioneer W21, focused on getting crops away quickly to beat pests this autumn and believes it has worked well.
Most oilseed rape follows winter barley and is drilled with a farm-adapted power harrow drill featuring four winged tines that cultivate down to 150-200mm, double-disc coulters to sow three rows behind each leg and a press wheel to consolidate soil. This is followed by an extra pass with ring rolls.
“Our target seed rate was 80/sq m for conventional varieties and slightly less for hybrids and I’m confident everything we’ve sown has grown on most land. Some chalk land suffered a bit of capping, which limited crops slightly, but it hasn’t been a major issue.”
Flea beetle was identified in his area and he acknowledges the first metre or so of some headlands has suffered damage, but it is not clear whether this is due to beetles, slugs or pigeons.
Two insecticide sprays were applied across the whole rape area, with the first, 0.2 litres/ha of Permasect (cypermethrin), going on two to three weeks after drilling. A follow-up spray of 0.2 litres/ha Biscaya (thiacloprid) was then applied at the end of October to target aphids carrying turnip yellows virus (TuYV).
Mr Taylor says early-autumn nitrogen and sulphur fertiliser have also been key to establishing crops well. Nearly all oilseed rape ground received 30kg/ha of sulphur in mid-September, plus half the area also received 30kg/ha of nitrogen.
“We based applications on the size of the crop and whether it needed a boost, as our aim was to get as big a crop as possible going into winter to keep pigeons off and stay ahead of other pests and diseases.”
Strong crops with low pest damage
Richard Cotton, Devon
The 50:50 mix of hybrid and conventional varieties (including Quartz, Flash and Expower) were direct-drilled slightly later than planned, between 24 August and 8 September, but went into good seed-beds and had plenty of warm weather with adequate moisture to spur growth on, he says.
Very little flea beetle damage was seen and aphid numbers were not high enough to cause concern, but turnip sawfly did damage some crops that missed an early pyrethroid.
About 85% of the rape area received cypermethrin (Toppel at 0.25 litres/ha) with the first graminicide (Shogun at 0.4 litres/ha) in the third week of September. “It worked well and didn’t need a follow-up, but we did have to go back and treat those crops that missed this spray as soon as the sawfly started coming in.
“Some crops look so strong they may require a fungicide with growth regulatory activity.”
While Mr Cotton says the weather has been the biggest factor in the strong crop establishment this autumn, it has also been helped with an early application of 100kg/ha Di-ammonium phosphate (DAP) near the end of September to the majority of the oilseed rape area.
“We’ll see how the winter goes, but normally as soon as we get a sensible weather window in February, we’ll go back in and start nitrogen applications and also apply some ammonium sulphite.
Early insecticide limits damage
Peter Cartwright, Lincolnshire
About 200ha of oilseed rape (mainly hybrids DK Extrovert and Popular, plus Quartz and Trinity) is in the ground this season, out of a total 1,220ha of cropping.
Although flea beetles did start appearing in crops early in the season, significant damage was avoided with an early insecticide.
“Flea beetles were present and it could have gone either way, but our location and the favourable weather post-drilling allowed crops to grow away from any damage.
“It did take up a lot of my time, though, as I was walking rape crops almost constantly for a four-week period during the end of August and most of September, looking for signs of flea beetle.”
All oilseed rape received 0.05 litres/ha of Hallmark Zeon (lambda-cyhalothrin) at the first true leaf stage, about a fortnight after drilling. The most at-risk crops, accounting for about half the rape area, also received a follow-up spray of 0.25 litres/ha of Permasect (cypermethrin) about a week later.
“We were going through with a root growth promoter anyway, so it made sense to include a second pyrethroid where required.”
Like other growers, Mr Cartwright knows strong, early establishment has been vital in helping crops grow away from pest pressures. Rape was drilled between 23 August and 2 September using the farm’s adapted 3.5m Spaldings Flat Lift cultivator. Seed rates were up to 50/sq m for hybrids and 80/sq m for conventional varieties, and most of those seeds have established, he says.
Good seed-bed consolidation was key and he is pleased with the early signs from a part-field trial, where land was rolled twice after drilling, with the second pass at 45 degrees to the first.
“It was difficult to see any difference in establishment early on, but there is a clear visible benefit now in terms of stronger crop growth where we used the approach. A lot of that is to do with better seed-to-soil contact in the dry September, rather than tighter seed-beds keeping insect pests out.”
Good weather favours OSR crop
Jim Cargill, Aberdeen
His 40ha of Mendel oilseed rape was direct-drilled with a Sumo Trio on 20 August at a rate of 1.6kg/ha and he says crops look good going into winter, thanks largely to favourable weather this autumn.
“Our target plant population is 30/sq m and we should be somewhere near that. Switching from a plough-based system allowed us to get all oilseed rape drilled in good time and crops have established well.”
That strong early establishment has always been key for Mr Cargill, given the risk of crop losses in harsh winters, but especially so with the loss of neonicotinoid seed treatments this season.
While no insecticide was needed this autumn, he would have gone with Biscaya or Plenum (pymetrozine) as he believes pyrethroids are now ineffective against aphids in oilseed rape.
“As soon as any risk is highlighted, we will spray, but luckily this year neither flea beetle or aphids have been an issue for us.”
Reports of pyrethroid resistance in England concern Mr Cargill, who fears the situation could worsen as more demand is placed on remaining chemistry. “We don’t know whether there is resistance to pyrethroids here, so there is always an element of doubt as to whether insecticide applications are going to be fully effective.”
Establishment was also boosted with early nitrogen and phosphate fertiliser. Half of the rape area received hen pen poultry manure prior to drilling, while the remainder had an application of 30kg/ha nitrogen plus 180kg/ha phosphate.
Crops did receive a pre-emergence herbicide of Butisan (metazachlor) plus clomazone. Mr Cargill says slugs were a bigger issue this year due to more surface trash from direct drilling and mild, wet weather.
We’ll be following the fortunes of our four growers throughout the season – to see how their different strategies pay off and how their crops fare. Our next update will be published in the May issue of Crops magazine.