Arable News

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Protect water from OSR herbicides

Oilseed rape growers have been issued with revised, and more stringent, guidelines relating to autumn applications

Oilseed rape growers have been issued with revised, and more stringent, guidelines relating to autumn applications of herbicide metazachlor to help reduce its impact on drinking water. Dominic Kilburn writes.
Ignore new guidelines for the use of oilseed rape herbicides this autumn and fail to reduce pesticide concentrations in water, then the likelihood is that decisions relating to key OSR active metazachlor, and other herbicides such as carbetamide, propyzamide and quinmerac, will be made on a restricted basis, growers are being warned.

The recommendations for metazachlor (see Table 1), are mostly focused around dose rate and timing of applications, and have been made by crop protection companies Adama and BASF as part of the ‘Metazachlor Matters’ stewardship campaign, an initiative launched last year on the back of diffuse pollution from pesticides threatening the UK’s chances of meeting objectives of the Water Framework Directive (WFD) – the EU legislation to protect all surface and ground waters.
Speaking at an event in London recently, BASF’s head of business development and sustainability, Rob Gladwin (left), said that metazachlor and quinmerac remain essential components of early season herbicide programmes in oilseed rape. “OSR remains the most profitable arable break crop, even with recent declines in commodity prices, and it’s still a significant element of crop rotation.
“In addition, it’s an important crop on heavy land where spring crop establishment is more difficult, while providing an opportunity in the rotation to control problem weeds including black-grass,” he explained.
“Most oilseed rape crops will receive an application of metazachlor in the autumn, and so we have got to take the threat of restrictions seriously – there is quite a bit at stake here for growers,” he stressed.

Treatment issues
According to Severn Trent Water catchment manager, Dr Jodie Rettino, also speaking at the event, concerns are growing about autumn-applied oilseed rape herbicides. “Water companies are struggling to remove high concentrations of a number of pesticides over the autumn and winter, including metazachlor, as, when they are found together, it makes it very difficult to treat,” she explained.
“There is a cost too,” she pointed out. “From one waterworks alone we treat about 26,000 megalitres (26 billion litres) per year to remove pesticides at a cost of #150/megalitre, and we have 16 waterworks in total.”
Dr Rettino said that Defra is looking to mitigate the risk under the WFD and that other ways of reducing it have to be looked at. “There’s an obligation under the WFD to solve the problem at source, rather than relying on treatment at waterworks, and so that means that more work is needed in catchments at the source of the problem,” she commented.
“There can be no resting on laurels and all parties involved in designated Safeguard Zones (at-risk catchment areas), including catchment officers, farmers and water companies, have to work together to reduce the risks – we don’t want to see a product ban come into force,” she added.
Metazachlor can get into water via two main sources (in the farmyard when handling, mixing or during the cleaning down process; and via the field as surface run-off or field drainage) and Adama’s senior crop team leader, Dr Paul Fogg (left) reiterated the importance of following Voluntary Initiative advice this autumn regarding best practice in the use of pesticides, pointing out that growers ‘thinking agronomically’ will help to minimise some of the risk of pollution via field sources, where some of the greatest challenges are represented.
“Key to success is to maximise establishment by getting the crop in the ground before the end of August,” said Dr Fogg. “Good consolidation of the seedbed is key for better performance of herbicide products; it minimises the amount of open seedbeds and the risk of product movement, and boosts herbicide efficacy.
“And the early removal of weeds maintains yield potential,” he added.
Getting the crop established early also helps its tolerance of flea beetle, slugs, pigeons and phoma, as well as setting the crop up with bigger plants going into winter, he suggested.
Rob Gladwin added: “Early application of metazachlor is particularly important on drained soils where the risk of movement increases the later you go, but, in general, growers should think about completing applications of metazachlor ideally by the end of September,” he said.

Are you in a Safeguard Zone?
Drinking water Safeguard Zones are catchment areas that influence the water quality at (surface) drinking water abstractions which are at risk from pesticide pollution. The zones are where action to address water contamination will be targeted so that extra treatment by water companies can be avoided.
There are 113 surface water Safeguard Zones in England of which 8 currently have been identified as having a metazachlor risk. Most are in the Thames Water region, central England and the West Midlands.
Growers are advised to visit the Environment Agency’s ‘What’s in your backyard? website ( to establish if they have fields in a higher risk area.

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