slug pelleting© Tim Scrivener

The Metaldehyde Stewardship Group is to launch an initiative to provide water companies with information enabling them to decide when not to abstract water from rivers this autumn.

The aim is to reduce the risk of water containing the active being pumped out of rivers into reservoirs.

Dinah Hillier of Thames Water explains that the metaldehyde issue came into particular focus in the wet year of 2012 when pumping water out of rivers ended up contaminating reservoirs.

See also: Water company launches trial to tackle slug pesticide levels

The main problem with metaldehyde is that it cannot be removed from water and levels are reduced by blending with water containing lower levels.

Smart abstraction

“Ideally we would stop abstraction when we know metaldehyde is in the river and start up again once the peak concentrations have passed,” she explains.

“Unfortunately, despite many years of trying, there is still no method for detecting metaldehyde in real-time, and sample collection and analysis doesn’t allow for a quick enough response.”


Dinah Hillier of Thames Water © Tim Scrivener

The reservoirs west of London include The Queen Mother reservoir, which itself holds 38bn litres of water and water is pumped out of the river Thames.

“We need to fill up before the next summer and want to do this when electric prices are lower. Therefore, periods over which we can stop abstracting have to be limited.”

To help predict elevated levels, Thames Water has produced a computer model, Metpred, which uses weather and other information like soil water deficit. “Last year, we stopped extracting, but levels didn’t rise as pellets had not been applied.”

She says the timing of metaldehyde slug pellet application is a critical missing piece of information in the model.

Agronomist role

That’s where the MSG initiative comes in. A group of 20 agronomists are being enlisted to provide information, explains David Ellerton, technical development director at Hutchinson. This includes progress of drilling, crop growth stage and slug pellet use.

“The aim is that about 20 individual advisers will use a reporting system to provide feedback from different geographical areas,” he says.

“The initiative will be up and running in advance of the first metaldehyde slug pellet treatments to oilseed rape crops in late summer and continue through the autumn and winter.

“Each adviser will fill in a short weekly report outlining the local soils conditions, weather summary, progress of drilling and crop growth, reporting the metaldehyde treatments that have been applied and that are planned imminently.”

The agronomists are being recruited through the Agricultural Industries Confederation and Association of Independent Crop Consultants.