Anglian Water is celebrating after a trial led by the water company led to a massive reduction in the amount of a pesticide making its way into drinking water in Eastern England.

The pilot programme was launched last year. Farmers within the natural catchments of six reservoirs in Northamptonshire, Suffolk, Essex and Cambridgeshire - an area covering 7,000ha - agreed to work with water company advisors to look at their control strategies and use alternatives to metaldehyde to control slugs on their land. Farmers used ferric phosphate in place of metaldehyde, which breaks down more quickly than the more popular pesticide.

In its first year, the trial resulted in a 60% drop in levels of the chemical detected in reservoir tributaries.

Metaldehyde is currently the most popular molluscicide with farmers, but the chemical has frequently entered drinking waters, causing concern as it is impossible to remove with conventional water treatment processes. This has led waters in some parts of the UK to regularly breach European standards (0.1 micrograms per litre - or parts per billion).

Anglian Water said all 89 farmers from the sensitive catchment areas approached by the company agreed to take part in the trial, and an estimated 1,613 kg of metaldehyde was removed from the farmed landscape as a result of the scheme.

Levels of metaldehyde detected in the Hollowell and Ravensthorpe Reservoirs in Northamptonshire were compliant with regulations and remained below the statutory limit during the trial’s first year. In Alton Water in Suffolk, Ardleigh Reservoir near Colchester, Pitsford Water in Northamptonshire and Grafham Water in Cambridgeshire there were still exceedances but overall levels were reduced significantly.

Commenting on the success of the trial, Anglian Water’s Catchment Strategy Manager Lucinda Gilfoyle said, “This has been a first, not only for us but for both the water and farming industries as a whole, and the data we have gathered will prove invaluable for tackling this thorny problem. What the first year of our trial has revealed is that by working together we can reduce metaldehyde levels in raw water sources – but that removing metaldehyde from the fields is not the silver bullet solution some may have hoped for.

“We know that a more detailed and longer term strategy is needed if we are to comply with pesticide regulations, and we will be building on these results as we move forward to help identify the package of measures needed.

“I want to say a huge thank you to all those farmers who have taken part so far – they have helped us build a valuable picture of pesticide movement and on individual farms they have proven that the alternatives to metaldehyde really do work in tackling slug damage.”

Sam Paske, Farm Manager of Hail Weston Farms Ltd who took part in the trial, added, “We were approached by Anglian Water to take part in this trial and it was something we definitely wanted to be involved in. If we are going to preserve metaldehyde for use then we all need to work together to ensure it doesn’t reach water sources.

“After speaking to the catchment advisor we made simple changes to our normal integrated approach to slug management. I have not noticed any difference between metaldehyde and the alternative ferric phosphate product – I know some people are unsure about it because you don’t see the dead slugs on the ground with ferric, but as long as I can see the crop growing I’m happy.”