There have been warnings over use of metaldehyde slug pellets following calls from Water UK, a body representing the UK's water companies, which said the substance has been detected at "concerning levels" in streams, rivers and reservoirs in England. Over the past two months, Metaldehyde has been found in water sources at levels four times higher than EU guidelines permit.

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In response to the warnings, the Metaldehyde Stewardship Group (MSG), part of an industry-led, voluntary approach to metaldehyde regulation, has "stepped-up the message to take extreme care with applications of metaldehyde slug pellets."

The group’s director, Dr Paul Fogg, claimed recent heavy rainfall had exacerbated the situation in the UK.  Monitoring by water companies revealed a geographic spread in incidents across England since September. The substance was present in water samples that failed EU safety tests in the greater London, Northern, Central and Eastern regions.

Dr Fogg said, "The situation is a clear culmination of circumstances where wet weather, a poor harvest, difficult establishment conditions and protracted crop growth have provided the ideal environment for slugs to thrive and breed. Meanwhile the usual ‘cultural controls’ such as rolling and generating a fine seedbed to deter slugs have been impossible to implement because of poor soil conditions. Crops that would normally have been in the ground for some time and that should be well established by now, remain vulnerable to attack as they have been slow to grow in the cold soil."

Though the year’s conditions have given rise to serious slug problems, Water UK spokesperson Phil Mills said, "Since late September this year, a number of companies have reported to the MSG that levels of metaldehyde have significantly increased in rivers and reservoirs across much of England. The levels have greatly exceeding the 0.1 parts per billion (ppb) standard for drinking water, which is the threshold for the majority of individual pesticides."

He added that "Peaks in metaldehyde have reached over 4ppb in several water catchments, with some river samples recording their highest ever value since intensive monitoring began in 2008." Metaldehyde is a particularly difficult chemical to remove from water, even using existing advanced water treatment processes.

MSG Chair Dr David Cameron suggested the industry group had brought in measures to tackle pollution since it was formed in 2008, including removing the highest dose metaldehyde products  and the addition of a statutory maximum rate of 700g/ha/year on product labels. Although Water UK's Mr Mills agreed that "MSG has done good things for voluntary guidance," he said “a robust solution is needed” and more must be done to ensure current guidelines are followed in the UK, including rolling out training and finding a sustainable solution which would avoid building new treatment systems to handle increased levels of metaldehyde in water, given that unpredictable weather is set to become the norm.

MSG chair David Cameron said the group’s 'Get Pelletwise' campaign has been successful in raising awareness of the issues around metaldehyde and ensured "best practice is communicated and understood," though he warned that, if a voluntary approach fails to generate sustainable reductions in levels of metaldehyde in rivers then legislators may impose restrictions to protect essential water supplies.

However, Nick Mole, a spokesperson for the Pesticide Action Network, suggested the extent of metaldehyde pollution raises questions about the effectiveness of efforts to communicate best practice. Mr Mole said, "I find the situation quite alarming considering the attention given to metaldehyde. Not least because the cost of removing metaldehyde from water is passed on to the consumer, so we are paying for treatment resulting from overuse or improper use of pesticides."

He went on to say that, Whilst PAN does support industry initiatives to ensure best practice is followed, the rise in metaldehyde contamination in water "indicates that the 'Get Pelletwise' campaign may not be effective," adding, "The question is, how many people have signed up to the campaign? How many are following the guidelines and how effective are those guidelines?" 

He concluded, "We have the potential for more unsettled weather; what we need to do is look at methods for dealing with pollution, not write it off as the result of freak conditions. If a voluntary approach is not working, then a legislative approach may be necessary. Otherwise, what’s going to happen when we have wet weather next year?"  

Metaldehyde Stewardship Group’s advice for best practice:

• Use minimum active per hectare to avoid drainage and runoff losses

• Maximum application rate 210g metaldehyde a.s./ha* For additional protection of water, suppliers/BASIS advisors may recommend rates reduced to 160g a.s./ha or less*

• Maximum total dose from 1st August to 31st December: 210g metaldehyde a.s./ha* For additional protection of water, suppliers/ BASIS advisors may recommend rates reduced to 160g a.s./ha or less*

• Maximum total dose rate: 700g metaldehyde a.s./ha/ calendar year*

• No pellets to be applied within 6 metres of a watercourse

• Do not apply when heavy rain is forecast

• If drains are flowing do not apply metaldehyde based slug pellets

*from any combination of metaldehyde products

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