Arable News

  • Written by: Farmers Guide
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Maintaining the metaldehyde message

With the new crop establishment season almost upon us, Dominic Kilburn gets an update from water companies on the battle to keep slug pellet active metaldehyde out of water, as well as some timely advice on slug pellet applications.

Although last autumn and winter was not the worst on record for slug pellet active metaldehyde exceedances being found in water, significant peaks were recorded and so growers and agronomists are being urged to do all they can to minimise the risk of contamination ahead of this season.

Metaldehyde-based slug pellets approved for use in the UK are still under-going regulatory risk assessment and re-registration, and so it’s imperative that growers follow enhanced stewardship guidelines laid out for metaldehyde pellet use as well as engage with the water industry.

That’s according to Thames Water catchment control manager, Dr Dinah Hillier (left) who says that the problem of metaldehyde getting into water is still very much here. “Last season wasn’t the worst we have seen but there were certainly some failures – some on a par with those that occurred in the benchmark 2012/13 season,” points out Dr Hillier.

“What we have learned though is that no two autumns are ever alike and although there were some wet periods last year, they fell between relatively dry times which helped.

“However, when it turned very wet in late December, there was some wash off from the fields and that’s when we got big spikes in metaldehyde being found. 

“The situation was exacerbated because river levels were relatively low and so there was little chance for dilution with cleaner water once the metaldehyde reached the rivers,” she adds.

Dr Hillier warns that if there was to be another autumn and winter of heavy rainfall along the lines of 2012/13, then significant failures could occur and further restrictions on pellets made from metaldehyde use would be likely. “Those growers in high risk areas of catchments need to try and look at alternatives to metaldehyde.

“Guidelines introduced last season including a 10m buffer zone around field boundaries and watercourses will almost certainly mean that, for growers in some situations, it’s unviable to continue to use metaldehyde.

“We need growers to engage more than ever with the water companies in a combined effort to improve water quality,” stresses Dr Hillier.


Since 2011 Thames Water has run a series of projects to encourage as many farmers as possible in high-risk areas where metaldehyde is a problem in drinking water, to engage with the company in return for payment.

In 2018, as many as 25 projects will be asking farmers to go about their slug control differently to increase the likelihood of keeping water in Thames Water river catchments free of metaldehyde.

Several different approaches are being tried to see what works best; in some areas farmers are being asked to substitute metaldehyde pellets for those containing ferric phosphate, with a subsidy paid according to the amount of ferric phosphate pellets used.

In other areas a ‘payment for ecosystem services’ approach is being offered, where the decision of how to keep water clean is left to the farmers and they are paid according to river water quality. This means that farmers can decide what works best for their farm, using cultural control methods such as use of a stubble rake, a switch to spring cropping and targeted low dose metaldehyde and ferric phosphate pellets.

Any non-organic farmer with land in arable rotation within the company’s project areas is eligible. To find out more email: [email protected]


Severn Trent catchment scientist, Adam Freer suggests that although it was a relatively dry autumn in 2017, several metaldehyde exceedances were recorded within the company’s catchment areas during the late autumn and winter that followed. However, he says that since Severn Trent introduced its scheme ‘Farmers as producers of clean water’ two years ago, metaldehyde concentrations recorded have reduced by about 50 per cent.

“The message to farmers that water starts on their farms and ends up in people’s taps has resulted in success across our catchments. There’s been a proactive approach to this from both sides and farmers have changed their practices to more sustainable methods of slug control by using a suite of cultural control methods, buffer zones and headland management, as well as some using ferric phosphate pellets as an alternative to metaldehyde,” says Dr Freer.

“It’s about farmers knowing the level of risk across different parts of their farms and only using metaldehyde in the right place and when it’s really necessary,” he adds.

Farm to tap

In mid July Severn Trent re-named its scheme to improve water quality by launching ‘Farm to Tap’, and continuing to offer farmers financial rewards and support for reducing levels of metaldehyde in their water sources.

Farmers in a ‘Drinking Water Safeguard Zone’, or in the Severn Trent priority catchments, are eligible to sign up to the Farm to Tap scheme, which offers up to £8/ha for reducing metaldehyde levels found in local surface water sources.

Alongside the financial support, every farmer that signs up will be assisted by their local Severn Trent agricultural advisers – experts who will work with them to develop the best solutions for their farm.

Additional bonuses are available and every farmer that successfully registers before 31 August will be eligible for a £25 early bird bonus towards their costs, says Severn Trent.

To find out the full terms and conditions of the scheme, and to sign up to Farm to Tap, farmers should contact their local agricultural adviser or email: [email protected]

Agronomic viewpoint

Northants based AICC agronomist Damian McAuley (left) is an advocate of using ferric phosphate-based pellets when and where he can, but specifically on field margins. Following last year’s MSG stewardship guideline introduction of a buffer strip to prevent any metaldehyde pellets falling within 10m of a field boundary, he has been impressed with the level of control even in these high pressure areas.

He said that, ideally, he would like to see a wholesale switch to slug control pellets containing ferric phosphate, however cost is the prohibitive factor. “Slug control comes down to having the right number of baiting points in the field according to the expected pressure and, because of their larger size, I’d have to use a significantly increased application rate of ferric phosphate pellets to cover the same area as when applying 3.5kg/ha of metaldehyde-containing, durum-based pellets.

“In my experience, the control gained from ferric phosphate is very effective and as good as metaldehyde, although you don’t tend to see so much evidence of kill on the surface.

“If we could get slug control with ferric phosphate down to the same cost as metaldehyde, then we simply wouldn’t have an issue with metaldehyde getting into water,” Damian added.

Looking to this autumn, and following weeks of exceptionally dry weather, he said that it will be interesting to see if slug populations have been affected.

“I don’t know whether the dry conditions will have affected their reproductive cycle or not, but the high populations of slugs witnessed in the spring have not gone, they have just moved deeper underground. Slugs typically move in the soil profile according to the moisture level and so it may be that they are reproducing as normal, but that much further down in the soil.

“Following what was a wet and late spring, there was certainly plenty of pressure in crops at that stage,” he added.

Risk factors

Ahead of crop establishment Damian urged growers to think carefully about their slug control this season. “Look at the risk factors: think rotations – particularly the likelihood of higher pressure following OSR; consider the wetter, heaviest parts of the fields and get out there in good time with traps to understand population levels.

“Thresholds must be met before applying metaldehyde,” he warned.

“Consider how well the straw is chopped and spread off the back of the combine and whether a straw rake is necessary to distribute straw and chaff evenly and disrupt any slugs on the surface,” he added.

“We’re in an era of less soil disturbance and while reduced tillage may disrupt slugs that are on, or very near to the surface, it doesn’t have an effect on populations further down. Reconsolidation of the seedbed after drilling is therefore critical, not only to prevent slugs moving around the seedbed but for good seed-to-soil contact, moisture retention and quicker crop establishment – particularly when other pests such as flea beetle in oilseed rape are considered,” he explained.

“A lot of my growers are increasingly looking at their ditches and drain management and how water-logged and poorly structured soils can affect run-off of soil particles, phosphate and actives such as metaldehyde.

“There’s a recognition that healthier soils will improve infiltration overall and have a better water- and input-holding capacity, reducing the amount of run-off when weather conditions deteriorate,” he added.

Damian reminded growers that it’s now a legal requirement to have slug pellet applicator kit NSTS tested – all slug pellet application equipment over five years old that is in use should have been tested by 26th November 2016 (or the first test due before the machine is five years old), and then every six years thereafter.

“Stick with the MSG’s stewardship guidelines, being sure of a maximum application rate of 210g/ha metaldehyde, and take care to keep metaldehyde pellets out of the 10m field boundary buffer zone by using ferric phosphate pellets around the outside of all fields.”


Use the right pellet at the right time 

Adama is urging arable growers to make every slug pellet count this season by applying the right pellet at the right time and at the right dose. In doing so, the crop protection company hopes growers can minimise the impact of key molluscicide active ingredient, metaldehyde, on drinking water quality and environmental diversity.

“Our on-going commitment to promoting the responsible use of agrochemicals and reducing the threat of key active ingredients being lost means we’re asking growers to think carefully about how and when they apply slug pellets,” explains Adama’s fungicide and molluscicide technical specialist, Andy Bailey. “That means ensuring all spreading equipment is properly maintained and calibrated before pellets are applied.”

To enable accurate spreader calibration without the use of live slug baiting pellets, Adama is giving away a limited number of 5kg bags of placebo pellets which are a perfect copy of the company’s own metaldehyde based slug pellets.

“While these dummy pellets perfectly replicate the ballistic characteristics of products such as Gusto 3, Carakol and Enzo, they don’t contain any active ingredient,” Mr Bailey continues, adding that growers can apply for the placebo pellets by visiting Adama’s website.

For growers in any doubt about when it is appropriate to apply slug pellets this season, Mr Bailey also advocates Adama’s WaterAware app featuring #SlugAware to firstly predict likely levels of slug activity, and then determine if climatic and soil conditions are suitable for applications to be made.

  • Written by: Farmers Guide
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