Dwr Cymru Welsh Water
Weed Wiper Partnership

MCPA is a selective herbicide commonly used on broad-leaved weeds in grassland. It's used in domestic products and agro chemicals. It's commonly used on rush infestations as the surrounding grassland is unaffected, and clovers mildly.

MCPA doesn't bind to soil particles so it's prone to leaching, directly into watercourses or via mole and land drains. Once in the water it can take 3-4 weeks to break down.

Investigations - Afon Teifi upstream of Llechryd Water Treatment Works

Following investigations in 2013 and 2014, it's been identified that MCPA is widely used for controlling the growth of weeds like the Common Soft Rush, which has flourished following wet weather periods in recent years.

Wetter weather puts pressure on land, increasing risk of compaction and poaching, overwhelming drainage and creating favourable conditions for rushes to grow.