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Catchment management – a way forward to maintain slug control choice?

Growers are being asked to use an alternative slug pellet active to metaldehyde for the season ahead in the four recently announced pilot catchments.

Growers are being asked to use an alternative slug pellet active to metaldehyde for the season ahead in the four recently announced pilot catchments. With the imminent demise of methiocarb, ferric phosphate is the likely alternative of choice.

Pincey Brook, a Thames tributary in Essex, is one of the pilot studies - so how are growers in the catchment embracing the voluntary scheme?

Daryl Henehan, water quality scientist at Thames Water, explains the thinking behind the pilot catchment. “Because metaldehyde  cannot be removed from raw water, there is pressure on all the water companies to show our regulator, the Drinking Water Inspectorate, that catchment management is a way of keeping metaldehyde at a level that allows us to meet the drinking water standard of 0.1 parts per billion for pesticides.”

When the issue with metaldehyde first came to light, little was known about how it was getting into water. Studies have now shown that run off from fields and field drains is the main way metaldehyde is reaching rivers and reservoirs.

The new focus being promoted by the Metaldehyde Stewardship Group (MSG) is on a voluntary enhanced stewardship basis, targeted at fields identified as high risk in the pilot catchments. These fall within a ‘Safeguard Zone’ and the idea is to protect the catchment upstream of a Drinking Water Protected Area. They are advocating zero metaldehyde in identified ‘high risk’ fields.

The pilot studies are the result of collaborative work between the agricultural and water industries, environmental bodies and the metaldehyde manufacturers (who are represented by the MSG) to solve the problems posed by metaldehyde, which has been ongoing since it was first detected in raw water in 2008.

“Pincey Brook was chosen for this pilot because we have consistently seen high metaldehyde concentrations during four years of monitoring. It is not the worst catchment in the region and these results do not indicate poor farming practice,” stresses Mr Henehan.

Within the Pincey Brook catchment, risk levels have been identified on a field-by-field basis according to soil type, topography and proximity to a watercourse. “This approach is only a desktop exercise at the moment and needs to be tested in this pilot and the three other pilot catchments,” explains Mr Henehan.

“It is likely that the schemes will evolve further when they are up and running, especially regarding where to draw the line designating the high risk areas within the catchment.
We’re working hard with the agricultural industry and understand the need for them to protect their crops against slugs, but we need to show the DWI that this approach can work to manage metaldehyde by 2018,” warns Mr Henehan.

On the plus side, if catchment management can be shown as an effective way of keeping metaldehyde within acceptable limits for drinking water standards, then the scheme will be rolled out countrywide.

This would encompass eighty priority water catchment areas and would facilitate slug control choice, where metaldehyde could still be used outside of the ‘high risk’ field areas without compromising water quality.

In the meantime, the threat still looms of potentially losing metaldehyde, the most widely used active for slug control. With the imminent withdrawal from sale of methiocarb in September, it is in the whole industry’s interest to maintain choice in the options for slug control.

“Ferric phosphate is likely to be the alternative of choice,” comments Certis’ Robert Lidstone. “It stands up in terms of its environmental profile and with regard to efficacy and price it’s on a par with the best of the metaldehyde options. Sluxx is a quality, wet-process, pasta pellet which maintains a good level of integrity and more and more growers and agronomists are gaining experience and confidence in the product.

So how are growers in the catchment receiving the news that they are at the forefront of the enhanced metaldehyde stewardship campaign and spearheading a new approach to catchment management?

Independent agronomist, Matthew Paterson, has several growers with high risk fields within the Pincey Brook catchment. “The soil type is mostly chalky boulder clay and is largely under-drained, growing mainly combinable crops and some potatoes,” he explains.
“Farmers in the area generally have a progressive and forward thinking attitude and aren’t afraid of change.”

Risk of slug damage for the coming autumn is universally considered to be high after ideal conditions for breeding and survival. So how are growers in the catchment planning to protect their crops at risk of slug damage and how will it affect their current farming practice?

Growers are already using the integrated slug control practices being advocated within the catchment. “Ploughing is normal practice on this soil type and it not only buries surface trash but, along with subsequent cultivations, does a good job of disturbing the slugs’ environment,” says Mr Paterson. “Consolidation using a press or roll also plays an important part in getting good seedbeds for crop establishment and helps reduce slug damage.”

One of the main worries being expressed by farmers at a recent meeting in the Pincey Brook pilot, was their limited experience of ferric phosphate slug pellets and lack of confidence switching from metaldehyde, especially when crops are at a high risk of slug damage.

James Tubby, farm manager for Little Barrington Hall Farm, will be most affected by the pilot, with the vast majority of his acreage falling within the high risk area.

“We’ll be under high slug pressure if it becomes wet later, so I am nervous about using ferric phosphate for the first time but I’ve heard good things about it,” says Mr Tubby. “So far the season is earlier than last year so hopefully we will have more time to get better seedbeds and keep checking traps for slug populations.

“We’re all on the same page over the metaldehyde issue and, looking at the bigger picture, if we can’t make the pilot work then we’ll all be losing metaldehyde. We’re happy to work with the water companies and give it a go,” he adds.

Oxfordshire based independent NIAB TAG agronomist, Jon Bellamy, has been involved in a two year trial using ferric phosphate in the Thames’ Cherwell catchment where he has looked at the product scientifically with field scale monitoring. He believes confidence will grow as growers gain experience using ferric phosphate.

“Moving from metaldehyde is a slight leap of faith, metaldehyde has been around a long time and is tried and tested,” comments Mr Bellamy. “There are a couple of things about ferric phosphate which are different and growers need to get used to.

Ferric phosphate pellets are a bluey-green colour, which makes them more difficult to see than the bright blue pellets metaldehyde users are more familiar with and, instead of seeing slime trails and dead slugs littering the soil surface, slugs stop feeding and go underground to die.”   

Once you get over the hurdles of not seeing dead slugs and the pellets being less easily visible on the soil surface, the relative newcomer brings positive benefits and works at least as well as metaldehyde to prevent slug damage, adds Mr Bellamy.

“My growers already using ferric phosphate like it - as well as being able to use it to treat the headlands of fields, the pellets spread well, kill slugs effectively and are not hazardous to people, dogs or the environment. In terms of rainfastness, ferric phosphate is possibly better.”

During the two year pilot, Thames Water will share water quality monitoring results with farmers and are hoping to open the lines of communication directly with growers to help them manage the catchment.

“We understand that a grower’s first priority must be to protect their crops,” says Thames Water’s Mr Henehan. “The trial is voluntary but we are asking that if they do apply metaldehyde, for any reason, then please just let us know so that we can record where metaldehyde had to be used and relate it to water quality monitoring,” he concludes.