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Slug control with zero metaldehyde

As year one of the zero metaldehyde pilot catchment projects draw to a close, Teresa Rush caught up with one of the participating growers.


Harvest 2015 at Dyrham Park Farm, in Hertfordshire, marks the end of a cropping year in which no metaldehyde was used on the farm.


Andrew Gray is one of a number of growers participating in the first year of the four ‘zero metaldehyde’ catchment projects taking place across England. He and his family farm close to Barnet, just north of London, and within Affinity Water’s Mimmshall Brook catchment.


He is no stranger to the challenges of balancing commercial farming with growing pressure to meet water quality standards; he exited dairying in 2002 when increasingly onerous water protection legislation restricted slurry spreading on the farm to the extent the dairy enterprise was no longer viable.


Mr Gray farms 122 hectares of arable on the mixed beef/arable unit. Cropping on predominantly London clay soils comprises winter wheat, winter oilseed rape and winter beans. Mimmshall Brook and two of its tributaries run through the farm, which is one of 11 holdings with fields identified as being ‘high risk’ in terms of the potential for pesticides, including slug pellet active ingredient metaldehyde, to move into water. There are 55 holdings in total within the catchment.

Mapping exercise

Already involved with a Catchment Sensitive Farming (CSF) project, Mr Gray worked with Affinity Water and another local grower, Alastair White, on a mapping exercise to identify the highest risk fields across the Mimmshall Brook catchment. Some 85% of his fields are affected.


“Only a couple of outlying fields are not within the [zero metaldehyde] catchment,” he says.


The mapping process is to be further developed as the project enters its second year. Mr Gray believes it threw up a few anomalies this season; some fields which would appear to be obvious candidates for inclusion in the pilot on the grounds of their soil type, slope or proximity to a watercourse were omitted, for example. He is also sceptical about the practical value of identifying a part-field for inclusion and in addition feels the presence or absence of under-drainage should be included in the risk assessment criteria.


However, after seeing the results of the mapping for 2014-15 and with most of his arable land identified as high risk, he took the difficult decision not to use metaldehyde on the whole of the main farm.


“We are on heavy clay, a high-risk soil type for slugs. Our biggest use of metaldehyde was in wheat after oilseed rape and sometimes in oilseed rape to get crops through the first few weeks.


“Our ‘best case’ scenario would be a standard dose just as wheat had germinated. As soon as it had chitted we would put slug bait on and follow up in high risk areas or the whole field if it was really bad.”


During 2014-15 Mr Gray has used ferric phosphate slug pellets Sluxx in place of metaldehyde. He has been a firm believer in using longer-lasting quality metaldehyde pellets – cheaper materials break down more quickly and so the cost/day can in fact be higher than that of materials which are more expensive in the first instance, he says – and so he found there was little difference between the cost of the metaldehyde pellets he had been using and the ferric phosphate pellets.


“It was a straightforward switch. It is a good quality pellet. The only criticism I would have is the dye seems to fade quickly and so it can be hard to see if the bait is still there – or it is hard for your agronomist to tell if it has been applied.”

Mimmshall Brook catchment, Hertfordshire

  • 57 catchment area
  • 18% of catchment area high risk from diffuse pesticides (arable fields only)
  • One water treatment works supplying 250,000+ people
  • Agriculture accounts for 64% of land use
  • Established Catchment Sensitive Farming project and extensive water quality monitoring programme
  • 11 holdings with high-risk land in catchment


*Source: Affinity Water/Water UK


Mimmshall Brook catchment project 2015-16

Affinity Water agricultural adviser Sarah Asberry is hopeful growers in the catchment will go into year two of the project with more confidence after their experiences and success in year one.


Extra sampling is being done during 2015-16 to build on the data generated this far and sampling will also be done in fields not within the risk map.


The commitment of the growers involved in the Mimmshall Brook zero metaldehyde pilot is underlined by the fact all of the growers affected have agreed in principle to participate in the project during 2015-16. And perhaps one of its most significant achievements is raising awareness among farmers and growers of the risks associated with metaldehyde use, says Mr Gray.


He does not rule out using metaldehyde in seasons of high slug pressure. “It may be we have to use metaldehyde in a really bad year,” he says.


“But I think the scheme has made people more aware of when and how they apply slug pellets; they might think a bit more about the weather and they might now consider delaying applications.”

Mr Gray received no subsidy from Affinity Water to switch to ferric phosphate and purchased his supplies through his normal distributor, but the water company did pay for participating growers’ slug pellet applicators to be calibrated.


He reports no problems with slug control this year, although slug pressure has not been particularly high – it was rated low-average across the catchment.


Cultural control methods are also an important part of the slug control strategy, particularly rolling after drilling, he adds.


“I didn’t have to resort to metaldehyde anywhere. I’m not even sure if we applied [ferric phosphate] twice anywhere.”


He admits ferric phosphate’s mode of action takes a little getting used to – slugs will die within three-six days of ingesting the material but not on the soil surface, as is the case with metaldehyde.


“It is easier to go out and see dead slugs and a few blue pellets,” he says.


Good engagement between water companies and farmers has been identified as one of the key factors where the zero catchment projects have been successful and Mr Gray also believes this is vital.


“A big advantage is we all know each other. If there is to be legislation in the future it is better if we all know what is going on.


“Our biggest worry is there will be legislation to stop us using metaldehyde in this area and then we will be at a disadvantage and could even cease to be an arable catchment. Keeping it voluntary and keeping everyone talking is critical.”


The good working relationship farmers have developed with Affinity Water in the Mimmshall Brook catchment have also seen them providing extra information to the water company in terms of when they have applied slug pellets.


“The principle could be applied to other chemicals as well. It’s a bit retrospective at the moment but there is potential to do it in advance. But it has to be voluntary,” says Mr Gray.


He admits to being concerned about the potential impact of water quality legislation on the availability of other agrochemicals, particularly with several oilseed rape herbicides currently under the spotlight. Their loss could see oilseed rape going the way of the dairy cows, he says.


This could pose a serious threat to the long-term future of his arable business, as alternative crop options are limited and with spring beans, for example, a number of the herbicides used are the same as those used in oilseed rape.


An unintended consequence of spring cropping as part of an integrated black-grass control programme or to comply with the three crop role, could be more herbicides finding their way into water, he says.


Zero metaldehyde pilot scheme

First year of zero metaldehyde water pilots delivers mixed results

Results from the first year of the industry-led Metaldehyde Stewardship Group’s zero metaldehyde pilot projects have highlighted the importance of farmer engagement in keeping the slug pellet active ingredient out of watercourses.


Water companies reported on results obtained from the four water catchments involved in the project at Cereals.


Overall, autumn last year proved challenging in terms of managing metaldehyde exceedances, with the first spikes measured shortly after heavy October rainfall. More catchments were affected by metaldehyde losses than in previous years and there were record short-lived metaldehyde spikes in several catchments. There were, however, fewer regulatory sample failures.


The results reported from the pilot catchments ranged from no evidence of reductions to significant reductions in exceedances of metaldehyde in raw water compared to those seen in 2013.


The first year findings come as metaldehyde continues to be subject to pressure as a result of its detection in water, threatening non-compliance with Water Framework Directive standards.


Speaking at Cereals, Affinity Water’s Alister Leggatt said: “These pilot projects trialled an approach where farmers with land located within a handful of high-risk catchments were asked not to apply metaldehyde on selected fields.”


The level of engagement and dialogue with farmers is seen as a critical factor.


“The best results were achieved where farmers got actively involved and were engaged in the risk mapping process. Where they were not engaged, it was clear making a treatment decision according to field risk had not been happening.”


Essex farmer and NFU combinable crops board member Tom Bradshaw, who represents the NFU on the Metaldehyde Stewardship Group (MSG), said it was important farmers were proactive in the management of metaldehyde.


“We can make a difference by targeting applications in the right ground conditions and at the right timing,” he said.


Three of the four catchments involved with the pilot project are to continue with the same approach in 2015, reflecting a wider indication from Defra targeted legislative restrictions remain an option for policymakers.


But according to Simon McMunn, of the MSG, the door is still very much open for targeted voluntary restrictions, where the desired reductions in metaldehyde can be achieved.


He said: “If this field-targeted approach does become adopted on a more official basis in future years, it could allow for metaldehyde to continue to be available to farmers outside of the highest risk areas.”


Anglian Water, which saw disappointing results in its Pitsford reservoir catchment in Northamptonshire, is developing a new strategy involving a dedicated catchment adviser and an incentivised metaldehyde substitution trial.


The company’s Slug it Out campaign aims to reduce the levels of metaldehyde in rivers and reservoirs.

Zero metaldehyde 2014/15 pilot catchment results

  • Mimmshall Brook, Herts: Water quality was improved compared to 2013. Metaldehyde levels peaked at 0.108ug/litre in November, compared to 0.322ug/litre in 2013
  • Leam, West Midlands: Water quality was slightly worse than in 2013. Metaldehyde levels peaked at 0.425ug/litre in November 2014, compared to 0.381ug/litre in 2013
  • Pincey Brook, Essex: Water quality was improved compared to 2013. Metaldehyde levels peaked at 0.215ug/litre, compared to 1.427ug/litre in 2013
  • Pitsford, Northants: No improvement in water quality


As part of the campaign the company is carrying out a trial project around six key reservoirs helping farmers to move away from metaldehyde and use an alternative chemical instead. Farmers will receive payments to cover their costs and for taking part.


In addition, a new team of five catchment advisers will be talking to farmers and agronomists about ways they can help reduce the amount of metaldehyde which finds its way into rivers and reservoirs.


Lucinda Gilfoyle, who is heading the campaign, said: “This is a whole new way of working for Anglian Water, so it’s exciting for us. Our aim is to work in partnership with the farming community to improve the region’s water quality.


“We have gathered a great team of experienced advisers and they will be talking to all the farmers in the target areas over the coming days and weeks. We will be watching the results of this trial closely to plan the way forward.”


Farmers eligible to take part in the trial project have land within the natural catchments of six reservoirs – Alton Wate,r in Suffolk; Ardleigh Reservoir, near Colchester; Hollowell Reservoir, Ravensthorpe Reservoir and Pitsford Water, in Northamptonshire, and Grafham Water, in Cambridgeshire.

Agronomists called on to help water companies manage metaldehyde

Agronomists from across the UK are being approached to help water companies to more effectively manage raw water abstractions to keep slug pellet active ingredient metaldehyde out of watercourses.


According to Dinah Hillier, of Thames Water, so-called ‘smart’ abstraction – stopping abstraction during periods when metaldehyde is known to be present in rivers – can provide a partial solution but is not a replacement for existing on-farm measures.


This is because the periods during which abstraction can be stopped are limited by the need to refill reservoirs after the summer, abstraction needs to take place during lower electricity tariff time periods and there is currently no way of detecting the presence of metaldehyde in real-time.


Computer modelling can be used to help predict when metaldehyde is likely to reach abstraction points, but an important piece of information currently missing is the timing of slug pellet applications.


Ms Hillier says: “This is where assistance from agronomists is so important.”


In a new initiative for the 2015-16 season, the MSG had been coordinating an agronomist recruitment effort though AIC (distributor agronomists) and AICC (independent agronomists) to help supply this information on a weekly basis.


David Ellerton, technical development director with agchem distributor and agronomy advice business Hutchinsons, says: “The aim is about 20 individual advisers will use a reporting system to provide feedback from different geographical areas. The initiative will be up and running in advance of the first metaldehyde slug pellet treatments to oilseed rape crops in late-summer.”


The service could provide an important link between the farming industry and water companies in tackling the metaldehyde issue, adds Dr Ellerton.

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