The UK’s largest ever metaldehyde-free farming trial has been expanded after successful first year results achieved a 60% drop in levels of the chemical detected in reservoir tributaries.

Year two of the Slug It Out campaign will see it extended to include Rutland - the largest natural catchment in the UK for a reservoir at 7,500 hectares - effectively doubling the trial’s hectarage.

The trial will continue for a second year in the natural catchments for six reservoirs in Northamptonshire, Suffolk, Essex and Cambridgeshire. Once again farmers in these areas will be asked to agree to use alternative slug control options to metaldehyde on their land.

Average metaldehyde levels in reservoir tributaries brought down by 60%

Last year, Anglian Water’s team of advisors worked with 89 individual farmers - a 100% uptake. The trial area removed an estimated 1,613 kg of metaldehyde from the farmed landscape, bringing the average levels in reservoir tributaries down by 60%.

Slug It Out 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 of water in an Olympic sized swimming pool.

In the past, levels in reservoirs in the region regularly exceed this and removing metaldehyde through treatment is currently not possible. Metaldehyde is not harmful to humans at current concentrations but its presence at the levels found means UK drinking water breaches quality standards.

Lucinda Gilfoyle, Catchment Strategy Manager for Anglian Water, said:

“We’ve made great strides in the first year of the trial, which at this scale, was an industry first – not only for Anglian Water but for both the water and farming industries as a whole.”

“Thanks to the proactive reception and cooperation from the farmers in our region, we’ve built a valuable picture of pesticide movement on individual farms and proved metaldehyde alternatives really do work in tackling slug damage.

“The trial has also revealed that by working together we can reduce metaldehyde levels in raw water sources.”

“I’d like to thank all the farmers who took part last year; their forward-thinking has yielded valuable data that will help us raise these challenges with policymakers to find sustainable solutions for both our sectors for the future.”

Water and agricultural sectors faced with navigating "thorny regulatory issue"

Lucinda Gilfoyle went on to say that both industries are faced with navigating a “thorny regulatory issue” and it was essential to work together to tackle it. In order to comply with pesticide regulations, a more detailed and longer term strategy was needed, which also takes account of non-agricultural and domestic use of metaldehyde.

Extending Slug It Out for a second year and expanding it to include Rutland will allow Anglian Water to verify its findings over an even larger farmed area and timeframe, building on the evidence base and helping to identify the package of measures needed.

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 is less soluble in water so is less likely to end up in watercourses when it rains.