Metaldehyde in the Thames Catchment: An update from the water companies 04/01/19

Metaldehyde in the Thames Catchment_59536

Metaldehyde in the catchment

As you may have already heard, Defra announced on 19th December that all outdoor uses of metaldehyde are to be banned from spring 2020. We understand that this is very disappointing news for the industry, especially with the hard work many of you have put into our projects to help protect water. It is worth noting that the ban is not because metaldehyde has been polluting drinking water sources.  The decision follows advice to government from the UK Expert Committee on Pesticides and Health and Safety Executive that metaldehyde poses an unacceptable risk to birds and mammals. All outdoor uses of metaldehyde will be phased out over the next 18 months. It will be legal for distributors to sell metaldehyde products for the next six months, with use of the products then allowed for a further 12 months.

In preparation for the phasing out of metaldehyde over the next 18 months, consider reducing your reliance on chemical control measures by adopting a wider range of options in your Integrated Pest Management (IPM) programme to control slug numbers. If you need to use chemical control, use ferric phosphate-based pellets instead of metaldehyde and, as always, follow stewardship and best practice guidelines. In some areas there are water company funded initiatives available to support you until the ban comes into force, so contact your local water company to find out more. Note that contact details can be found at the bottom of this update.

Please see the map and graph below for 12 monitoring locations within the Thames catchment.

Latest Results

The latest samples results show that metaldehyde concentrations have remained below the drinking water standard at all 12 monitoring sites, despite significant rainfall in the days prior to sample collection. Rainfall is predicted to be minimal over the coming week, however the cooler weather means that soils will remain moist and there is the risk that rain later in the month could mobilise metaldehyde from slug pellets that have already been applied. If you need to make any further slug pellet applications this autumn please consider water protection, use ferric phosphate and as always, follow best practice guidelines (

Catchment Infographic_59535

Focus on… Cherwell at Enslow

Metaldehyde concentrations in the River Cherwell at Enslow have exceeded the drinking water standard 38 times in the past, almost every autumn since monitoring began in 2011. The highest concentration recorded at this point was in autumn 2012, with a peak of 2.49µg/l, nearly 25 times the drinking water standard. However, so far this autumn, concentrations have remained below the 0.1µg/l standard, which is great news and possibly a result of what farmers have been doing in this catchment to protect water from metaldehyde contamination.

Cherwell at Enslow_59534

To find out more please contact:

Affinity Water: Q2F0Y2htZW50TWFuYWdlbWVudEBhZmZpbml0eXdhdGVyLmNvLnVr, SES Water: Y2F0Y2htZW50QHNlc3dhdGVyLmNvLnVr, South East Water: Y2F0Y2htZW50QHNvdXRoZWFzdHdhdGVyLmNvLnVr or Thames Water: Y2F0Y2htZW50Lm1hbmFnZW1lbnRAdGhhbWVzd2F0ZXIuY28udWs=

Last edited on: 03:01:2019

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