The new rate follows the withdrawal of 38 slug pellet products over the past year and the latest 2010 metaldehyde guidelines announced in May.
Metaldehyde Stewardship Group (MSG) representative Anne Fletcher said the CRD's decision brings the legal maximum annual dose rate for metaldehyde into line with MSG's guidelines at 700g/ha/calendar year.
She said: "Previously there was no set maximum total dose rate for the active ingredient - in effect meaning that the amounts of metaldehyde applied were unlimited."
East Anglian agronomist Colin Myram supports the changes. He said: "It signifies how seriously the industry is taking what has, up to now, been a voluntary campaign to prevent metaldehyde entering watercourses.
He added: "This season we have seen manufacturers withdraw products containing more than 700g of metaldehyde per individual application. They have gone even further in revising the MSG guidelines that now set a maximum total dose of 210g between the key dates of 1 August to 31 December - when the issue of metaldehyde reaching watercourses is at its peak."
The maximum recommended individual dose rate is 210g of metaldehyde/ha. It may be reduced to 160g or less on the recommendation of BASIS advisers.
Myram said latest developments showed that the agricultural and horticultural industries had recognised the significance of the water issues associated with metaldehyde use and showed just how seriously the threat was being taken.