Chlorotoluron is being found in a key Scottish water catchment area at higher levels than isoproturon was before its withdrawal, delegates heard at the Crop Protection in Northern Britain conference.

Since IPU was withdrawn, levels of chlorotoluron, a residual herbicide used to control grass and broad-leaved weeds, had been rising in the River Ugie catchment, said Fiona Napier from the Scottish Environment Protection Agency. “It is now being found at levels higher than IPU was previously, which is something the industry needs to consider.”

Concentrations within the catchment varied, but were sometimes high enough to result in a failure to comply with drinking water standards without treatment, Scottish Water had found.

“It is an unacceptable situation for our customers,” said Sarah Gilman, water regulation co-ordinator for Scottish Water.

It didn’t represent a serious health risk, she stressed. “But it is non-compliance, so we need to educate farmers on the potential issues surrounding diffuse pollution of pesticides, and in particular chlorotoluron and possible alternatives,” she said.

Pesticides had been identified as the main threat from arable farming to the environmental quality standard of water during catchment studies in Scotland, as part of the implementation of the Water Framework Directive. Various other active ingredients, including metazachlor, mecoprop, MCPA and metaldehyde, had also been found during monitoring.

In total, more than 5,000 breaches of the Diffuse Pollution General Binding Rules (DP GBR) had been recorded across 14 catchments in Scotland, which have been prioritised by SEPA for action to improve water quality.

The DP GBR covers farm activities such as cultivation, pesticide application and storage and application of fertilisers. It promotes good practice and gives a standard set of rules for farmers to adhere to.

The breaches highlighted the challenge the industry faced to improve water quality, said Susan Arnott, catchment coordinator at SEPA.

“In order to get an understanding of what was going on in the catchments, we walked the burns and rivers, as we had no idea exactly what was influencing water quality and where,” she said.

That approach was enabling a better understanding of sources of pollution, with better sampling technology leading to faster response to pollution events.

“SEPA is trying to raise awareness in these particular catchments, educating both farmers and advisers,” said Ms Arnott.

“One-to-one engagement is vital and the diffuse pollution audits we are carrying out assess compliance across the whole farm, which identifies good and bad practices and implements a planned timescale for mitigation,” she added.