Growers are being warned about the importance of observing slug pellet stewardship measures this autumn, as concern mounts over the detection of high metaldehyde levels in many UK water catchments.

Extreme care is needed with slug pellet applications, warns the Metaldehyde Stewardship Group (MSG), which accepts that growers are struggling with the highest slug pressure for many years.

But Water UK’s findings that peaks in metaldehyde have reached more than 4ppb in several water catchments in the past three weeks puts an even greater urgency on the message, stresses MSG chairman David Cameron.

“These levels are some of the highest since intensive monitoring began in 2008,” he says. “It’s vital to work together to try to prevent any further exceedances occurring.”

Slug pellet use in 2012 is already estimated at three times greater than last year, points out MSG’s agronomist Colin Myram.

“There has been a need for multiple applications,” he acknowledges. “Breeding conditions have been ideal for slugs, the pest population is far bigger than first thought and crops are being drilled late, often into poor seed-beds, which can’t be rolled as they are so wet.”

Continued heavy rain has also made it difficult to time pellet applications. “In some areas, drains have been running for a while.”

Paul Fogg, MSG’s spokesman, admitted that preventing field losses of metaldehyde through drainage and run-off posed a significant challenge this year.

Do the stewardship guidelines need to change?

The Metaldehyde Stewardship Group will be reviewing their guidelines at the end of the year, when all the testing results are in and the picture is complete.

The exceptionally difficult year will have to be put into context as the focus of preventing problems continues, notes Mr Myram. 

“The usual cultural controls used to deter slugs have been difficult to carry out this season, due to poor soil conditions. Growers need to protect what they have got in the ground – the slug pressure is likely to continue while it remains mild.”

He reminds growers the maximum total dose from the beginning of August to the end of December is 210g of metaldehyde a hectare. “Over the course of the calendar year, the maximum is 700g of active a hectare.”

Pellets should not be applied within 6m of a watercourse or when heavy rain is forecast, or if the drains are flowing. “These last two points have been so difficult this year. The weather forecast hasn’t been very accurate and deluges have occurred unexpectedly.”

This has certainly been the case for Gloucestershire farmer James Cox, who recorded rainfall on 24 out of the 31 days in October, bringing a total of 130mm for the month. He describes the ploughed ground as “crawling with slugs”.

“None of our crops have been rolled because the ground conditions are so bad. For the first time ever, we are looking at 15% of our oilseed rape crop failing.”

He had no need to apply pellets last year and has never had to use more than one application on the farm near Tetbury.

“In contrast, this year I’ve already put two applications on to the oilseed rape and one on the winter wheat. I would have put another on the wheat this week, but heavy rain was forecast.”

He is determined to follow best practice and minimise their use wherever possible. “Unfortunately demand has been so great that it’s been impossible to switch to the alternative active ingredient, ferric phosphate. Supplies simply aren’t available around here.”

Mr Cox admits to a great deal of thought before making a second metaldehyde application. “We always trap, to ensure thresholds have been reached, and we treat hotspots rather than the whole field.”

His pelleting equipment has been calibrated and a tray test done to check spread pattern. “We also delay any applications if the drains are flowing. We are just as concerned about the metaldehyde issue as the water companies are.”

More on this topic

Read more on the water companies warning over metaldehyde levels this autumn