Catchment advisor

The first year of the UK’s largest ever metaldehyde-free farming trial has seen a 60% drop in levels of the chemical detected in reservoir tributaries.

Farmers within the natural catchments of six reservoirs in Northamptonshire, Suffolk, Essex and Cambridgeshire have been working with Anglian Water’s team of advisors over the past year on the Slug It Out campaign. The area covers more than 7,000 hectares and as part of the campaign all farmers have agreed to use alternatives to metaldehyde to control slugs on their land.

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 (or parts per billion) in treated water. This is the same as one drop in an Olympic sized swimming pool. In the past, levels in reservoirs in our region regularly exceed this and removing metaldehyde through treatment is currently not possible. It is not harmful to humans at current levels.

The first year of the trial saw 89 farmers signing up to take part – a 100% uptake. The trial area covered 7,679 hectares and an estimated 1,613 kg of metaldehyde was removed from the farmed landscape.

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.

The average levels of metaldehyde in reservoir tributaries across all the catchments fell by 60%, while the average peak levels detected within the reservoirs fell by 26% (see full table in editors notes). Reservoirs are filled by water pumped from nearby rivers as well as being fed by tributaries.

Lucinda Gilfoyle, Catchment Strategy Manager for Anglian Water, 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 which manages land within the Grafham Water catchment took part in the trial.

He said: “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.

“The trial was clearly beneficial to the farm business and was well supported by Anglian Water.”

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 the alternatives are growing in use, in particular those using the active ingredient ferric phosphate. Ferric phosphate breaks down much more quickly than metaldehyde.