The measure is part of a set of new guidelines published last week and builds on the success of MSG's "Get Pelletwise" campaign - believed to have helped reduce the levels of metaldehyde exceedances detected by water companies at raw water abstraction points last year.
This year's guidelines are more stringent because a water catchment study carried out by the group has demonstrated that diffuse losses through the soil and into soil drains during high rainfall periods - particularly in autumn - are to blame for the majority of the metaldehyde detected in watercourses.
Dr Paul Fogg, who led the water catchment study, commented: "While factors such as direct application into ditches and spillages remain important, the study showed diffuse losses through soil drainage when the field drains are flowing as being most significant.
"What we found was that moisture moving down through the soil profile will take the metaldehyde from recently-applied slug pellets into the network of field drains and from there into the streams, ditches and watercourses, which may ultimately lead to a drinking water abstraction point."
For this reason, a new maximum single application rate of 210g metaldehyde per hectare has been set - down from 250g.
Additionally, the total recommended dose rate of metaldehyde applied from 1 August to 31 December has been cut to 210g metaldehyde per hectare.
There was previously no restriction during this time frame other than a maximum advised dose rate for the calendar year.
"For growers, the use of pellets is most likely to be in the spring so the new restrictions mainly apply to farmers of rapeseed and cereals," Fogg told Grower. "That said, diffuse losses are far more significant than we realised so we need to be cautious at all times of the year."
The new best practice guidelines maintain the annual maximum advised dose rate for the calendar year at 700g.
Published: 22/05/2010
Source: http://www.hortweek.com
