Clearfield oilseed rape - a bright future with DSV

“Clearfield oilseed rape - the future’s bright,” according to Michael Farr, Southern and Western Sales and Marketing Manager for the international plant breeder, DSV.

Michael sees this new technology helping with problem weeds but also increasing the overall viability of oilseed rape growing across the UK. ”In the future I would predict around 10% of the planted rape area in the future will be planted down to Clearfield.” he says. “We have seen very pleasing results with Clearfield in the field already.”

So how does the Clearfield system work? BASF’s Clearfield production system combines hybrid oilseed rape varieties with the use of a high quality post-emergence herbicide. Using conventional plant breeding techniques, rape varieties have been developed to tolerate the Clearfield herbicides such as Cleravo (imazamox and quinmerac) and Clerando (imazamox and metazachlor.) Applying a Clearfield herbicide to a Clearfield rape variety means excellent weed control including some of difficult weeds such as charlock, runch and shepherd’s purse as well as controlling other weeds such as chickweed, cleavers, crane’s-bill, red dead nettle, fumitory, groundsel and mayweed, whilst the crop grows unaffected. Clearfield varieties are always distinct by having the CL suffix as part of the variety name.

Clearfield rape from DSV

DSV is an international plant breeder featuring oilseed rape, Clearfield rape, winter wheat and maize varieties. It comprises of a German parent company based in Lippstadt with fully consolidated subsidiaries in the Netherlands, Denmark, France, Poland and the UK. It has a workforce of 600 employees and achieved sales in 2015/2016 financial year of 167.7 million Euros. As a breeding company with a long term focus, DSV aims to continue investing in R and D for the future, including Clearfield.

Why Clearfield?

DSV are one of the key plant breeders involved with Clearfield in Europe. Clearfield varieties are now yielding much better than those a few years ago and can match or even exceed the yield of non-Clearfield ones. The DSV Clearfield variety Veritas CL yielded a stable 106% compared with other varieties in the NIABTAG trials last season. Michael Farr of DSV reports that Veritas CL yielded exceptionally last year, well above the average in what was generally a poor yielding year. If you take into account that the NIABTAG trials are done on low weed pressure sites, growing Clearfield and controlling of weeds will have an even more positive impact on yields as weed competition is removed.

Many Clearfield varieties appear to have a more rapid start than non-CL ones. DSV Clearfield variety Veritas CL is noted for its high autumn vigour. Growers have commented on the fact that Clearfield varieties establish well and get away fast. Some growers are of the view that they may be unhindered by potential ALS herbicide residues in the soil left from ALS herbicides applied late in preceding wheat crops. With the early vigour, CL varieties may well help with cabbage stem flea beetle attacks, too, but this needs further work to fully understand.

The majority of Clearfield herbicide is usually applied in October, when the target weeds are small. This timing will help farmers to spread their heavy autumn workload and most importantly allows them to assess the viability of the rape crop first, before they start to invest heavily in inputs.

Clearfield herbicides are applied post-emergence and are suitable for any establishment system that growers are tooled up to use. Most farmers would drill Clearfield rape the same drilling window as Non-CL rape, during the last week of August. Anecdotally some growers have said that growing Clearfield varieties was important to them because of the risk of potential erucic acid contamination of the sample going to crush. Controlling cruciferous weeds such as Charlock, hedge mustard and runch, which all have a high erucic acid content, means that erucic acid contamination in seed samples is avoided and the risk of paying any penalties as a consequence is minimised.

Michael Farr reports that DSV are planning to introduce new Clearfield varieties in the future– one variety next year will be Phoenix CL. “This variety has much improved yields and has excellent standing ability, good Phoma disease resistance rating, improved Light Leaf spot resistance rating and increased Verticillium tolerance as well as high oil content. We have another CL variety in National listing trials this year. I would say that the new Clearfield varieties are certainly a step or two ahead of the existing Clearfield ones and of non-Clearfield varieties, in terms of agronomic traits. Initially growers were concerned about yield performance of Clearfield varieties but there is no need for this concern with the new ones now. In my view these new Clearfield varieties under development are coming closer and closer to our already successful rape variety Incentive in terms of the overall agronomic package, which can only be a good thing.”

Clearfield in the field

Clearfield herbicides are flexible and have a wide weed spectrum.

Clearfield oilseed rape is no longer a niche crop, grown to control just the difficult cruciferous weeds, but an easier way of growing a reliable high yielding rape crop, says BASF.

Clearfield herbicides are all applied post-emergence, so you can decide later if the crop is worth continuing with. For all broad-leaved weed species the best weed size is between 2 and 4 true leaves and for grasses and volunteer cereals between 2 to 3 true leaves. Bigger weeds take longer to die and those with deep, well established roots can re-grow. Early emerging weeds such as poppy, crane’s-bill and mayweed can reach optimum size before other weeds. If this is expected to be a problem, then use an early application of metazachlor followed by Cleravo.

Imazamox is a foliar-acting active ingredient and it needs to cover the target weeds and be allowed to dry. A minimum of 2 hours should be allowed for the spray to become rainfast when applied to a dry leaf.

Although Clearfield herbicides can provide some suppression of black-grass, black-grass specific herbicides with an alternative mode of action for resistance management must be used in sequence. Propyzamide-containing herbicides applied later in the season are the most commonly used to provide this. Metazachlor can also be applied early in a sequence in order to slow down the growth of crane’s-bill, mayweed and poppies. A non-Clearfield variety spray with a Clearfield herbicide will be wiped out, so it is important to keep accurate field records.Careful management and record-keeping is vital, even when controlling volunteers in following crops. Clearfield voluteers can be controlled in following crops with normal herbicides but not ALS inhibitors. This leaves a wide choice for growers. ALS inhibitors can not control these volunteers as imazamox itseld is an ALS inhibitor.

Label - The recommended dose rate of Cleranda is 2 litres/ha, for Cleravo it is 1 litre/hectare. Always add 1 Litre/ha Dash HC to all Clearfield herbicides to improve weed control. Dash HC acts as a humectant, keeping the leaf cuticle hydrated and increasing uptake. Water volumes are 100 and 200 litres of water per hectare, using higher volumes where there is a risk of crop or weed shading and spray quality should be fine to medium.

NOTE Clerando (imazamox and metazachlor) and metazachlor used in sequence is subject to metazachlor Stewardship guidelines. In order to protect water, the use of metazachlor herbicides on drained land should be avoided after the end of September. This restriction would not apply to Cleravo as it doesn’t contain metazachlor.