The loss of neonicotinoids means the 2014-2015 oilseed rape crop is up against it from the off. But there are ways in which growers can – at least partly – compensate for reduced crop protection options.
That was the conclusion of a round-table discussion organised by Bayer CropScience and hosted by farm manager Russell McKenzie, who grows 230 hectares (568 acres) of oilseed rape as part of the 750ha (1,853 acres) of cropping he oversees across Cambridgeshire and Bedfordshire for D.J. Tebbit and John Sheard Farms. He is also one of Bayer CropScience’s small group of InVigour Developers, farmers hosting ‘real world’ oilseed rape trials for the firm looking at the effect of different input variables.
Russ McKenzie: Getting OSR in and away promptly is going to be our main focus. In the worst scenario, we could be spraying every seven days for three weeks for flea beetle, and we are not in a particularly bad area. So we need varieties such as Harper and DK Extrovert, which have that rapid establishment characteristic.
Jim Carswell: As well as drilling date and seed dressing selection, fast autumn development from cotyledon to first leaf, when the crop is at most risk, will be a critical variety trait. The danger lies in not monitoring this period closely enough should stop-start combining lead to stop-start OSR drilling and staggered establishment.
Hybrids’ rapid establishment benefits are well-proven, but influences such as farm flea beetle history and soil types – lighter land can be at greater risk – must also be factored in.
Adrian Cottey: There is a key difference between autumn vigour, which aids against adult flea beetle attack, and spring vigour, which helps the crop resist damage from their larval offspring.
Autumn and spring vigour are not always found in the same varieties. Spring vigour – the ‘recovery’ phase from winter – will be even more important now as we are likely to see more thin, autumn-stressed crops which need to get going in spring. This could be the killer for some slow spring developers. Hybrids can cope better with difficult conditions – even flea beetle larvae attack.
But fast developers such as Harper must not be sown before mid-August, as excessive early growth is undesirable. On the other hand, where drilling is delayed, varieties such as Harper and Fencer cope well right through to mid-September and still get away quickly.
Jim Carswell: Phosphite dressings such as Take-Off act as a stimulant, working on the growth point and the root system, so when the root emerges, it picks up that phosphite, helping plants produce more extensive root systems and growth. I would strongly recommend OSR growers specify such a dressing. Combined with the use of a starter fertiliser, it is well-proven to give OSR a head start. Soil analyses, alongside pH and organic matter assessments, will also help identify areas where corrections could bring benefits. It is pH in particular which is key to crop accessibility to phosphorus.
To get the crop quickly through those early stages, a small dose of perhaps 0.35 litres/ha of phosphite such as Nutri-Phite PGA at cotyledon stage, followed by, say, 0.5-0.75 litres/ha at 4-6 leaves depending on crop condition. It is something we are trialling this year.
Russ McKenzie: I have definitely seen the benefit of phosphite dressing and prefer to have it where possible. On heavier ground here, we are potentially at slightly less risk of flea beetle, and on balance, although I would want both phosphite and insecticide dressings, if it has to be a choice, the phosphite would be preferential to encourage early vigour as we will still have to spray even with a seed dressing.
Jim Carswell: Something with a high phoma rating, for example, will mean flea beetle protection can be prioritised over early disease control. In this way the decisions partly make themselves.
In terms of insecticides, some imported seed may be dressed with Mesurol (methiocarb), the standard OSR dressing in France for many years. As its application here is not allowed, we do not promote it here, but provided there is approval for a seed treatment in the country in which it has been treated, then export of seed treated as such is legal, and we do want to provide people with as much information as possible about what to expect from its use.
Although approval for methiocarb use has now been revoked here, seed treated this way in another country – it is still approved for use in France and Croatia – is perfectly legal to use. But it provides perhaps half the protection against cabbage stem flea beetle that Chinook did, and it is not systemic, so its protection only lasts up to leaf two at the latest. After that a foliar spray follow-up will be necessary where flea beetle is a threat. The other possibility, meanwhile, may be some seed coming in with tefluthrin.
Going without any form of treatment – a fungicide treatment is still strongly recommended – may be an option if you are in an area known to not have a significant flea beetle problem, but it will be essential to closely monitor risk using water traps, for example.
Peter Stacey: Seed-borne diseases may not be as important in oilseed rape as in cereals, but they can affect germination, so protection will help get crops away quickly and developing root bulk. If seed comes ready-treated with a fungicide, that’s likely to be thiram, which will give some control of soil and seed-borne damping-off type diseases such as rhizoctonia and alternaria.
If seed is UK-treated, there is the option of Hy-Pro Duet (thiram + prochloraz), which provides better control of autumn phoma, both seed-borne and early air-borne, which are quite yield-debilitating. That gives greater protection and more autumn fungicide flexibility.
Unfortunately, a decision between fungicidal and insecticidal protection may be required, as in the French approval system Mesurol-treated seed cannot also have a fungicide applied.
Prioritising is a matter of whether you are in an area prone to flea beetle. If so, it is a straight choice for an insecticide; if not then seed dressings should give sufficient protection. And for varieties with high disease ratings, such as Harper’s 9 for phoma, fungicidal seed treatment is slightly less important.
Jim Carswell: To get the crop out the ground quicker, early drilling, when soils are warmer, is important. That broadly means mid-August onwards. If you do not have the man and machine power to drill while wheat is still being cut, consider using a contractor.
Thick crops are undesirable, so if early-drilled crops get too big too quickly, use metconazole to regulate them so canopies do not get too big during autumn – 6-8 leaf rosette-like plants going into winter should be the aim.
In 2007, HGCA reported peak flea beetle activity had occurred around the third week of September in 2005 and 2006, so you do not want a crop at cotyledon stage at this timing. Work backwards, factoring in emergence time of roughly a fortnight, depending on conditions and geography. Crops should be at the 6-8 leaf stage and rosette-like going into winter.
It has been suggested later sowings of faster-developing varieties can reduce flea beetle damage risk, but bearing in mind those September HGCA peak beetle figures, I’m not sure. Getting ahead of flea beetle by drilling earlier with starter fertiliser and phosphite seed dressing will be a better strategy than trying to beat it by going later.
Russ McKenzie: We have cut seed rates gradually, but have not gone silly. With hybrids that has meant a 30-35 plants/sq.m target.
Sowing more than this can be costly and does not generally help produce optimal yields. I put a lot of emphasis on good soil temperatures, something which can be lost with delays in drilling – a 3degC drop from 12degC to 9degC in summer 2012 really made a difference. I am hoping the warm July will help to maintain good soil temperatures. We use subsoiler-seeding where some soils would benefit from restructuring, with the remainder of our oilseed rape established using either Claydon or Horsch drills. But we are looking at ways to improve the optimal seed placement with the subsoiler technique for this season with a lower disturbance leg.
The speed at which we can put the crop in is going to be key. Ideally I would like to do it all between August 12-20. Traditionally we would work to a mid-August start date and end-of-the-month finish.
Adrian Cottey: It is not just about the calendar, though. Adaptations may have to be made according to conditions. Planting OSR into bone-dry soil just because it is mid-August would be unwise. A small delay may improve soil moisture conditions, and this is where vigorous hybrids come into their own.
Jim Carswell: Applying nitrogen and especially phosphate with the seed at establishment will undoubtedly help get the crop away quickly. Last year in particular, when conditions were dry, was a great indicator of what was possible with seedbed N and P. In treated/untreated strip-tilled trials into stubble, within 14 days plants sown with fertiliser were away, with bigger, more expansive root systems and plants. A number of trials suggest this can ultimately lead directly to yield benefits, but many farmers prefer to focus first on getting the crop away, and deal with yield responses separately.
If you are in an NVZ, then you are restricted to 30kg/ha N, but modern drill technology means placement accuracy is very good.
Phosphate has a big influence on getting the plant out of the ground, but it will not move to the roots – the roots have to move to the phosphate, so if you can put some down at drilling, the roots will pick this up and this will drive the plant on. There are numerous methods of placing both solid and liquid fertiliser, but precision of placement is key. Much depends on the farm’s drill or seeding arrangement, but more drill makers are looking again at combine.
Russ McKenzie: We have been placing fertiliser for a couple of years, and refining our establishment systems to get it exactly where required. Traditionally we used apply 166kg/ha DAP to meet the crop’s early N and P requirements, keeping us within the NVZ limits, but when we moved to put a higher concentration in the row, we switched to liquid. That works well, but can be a pain when it blows all over the machine. I was sceptical about microgranules, but we tried placing them when we established one particular field, and noticed that where we had run out on half a tramline, the difference was evident early on and the treated crop flowered three to four days earlier. It is not always noticeable in the top growth, but its value is evident in root growth, which is the aim at that stage.