The trial was launched to look at how levels of metaldehyde in rivers and reservoirs could be brought below the strict European standard of 0.1 micrograms per litre in treated water.
The first year of the trial saw 89 farmers signing up to take part – a 100 per cent uptake. The trial area covered 7,679 hectares and an estimated 1,613 kilogrammes of metaldehyde was removed from the farmed landscape.
The average levels of metaldehyde in reservoir tributaries across all the catchments fell by 60 per cent, while the average peak levels detected within the reservoirs fell by 26 per cent.
Anglian Water 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.”
Slugs are one of the most devastating pests faced by UK farmers – wheat and oilseed rape are particularly affected.
Metaldehyde is currently the most popular pesticide for dealing with slugs – but alternatives are growing in use. In particular, those using the active ingredient ferric phosphate, which breaks down much more quickly than metaldehyde.