Minimise establishment costs with low-dose slug killer

Slug numbers are building in many areas following recent unsettled weather, which is likely to prompt a surge in slug pellet orders over the next few weeks.

With grain prices under pressure metaldehyde, rather than the more costly ferric phosphate, could be first choice for many growers this autumn.

See also: Monitoring shows rise in metaldehyde ‘spikes’

While this is better for the bank balance, it could lead to further problems of metaldehyde being found in surface waters, especially if the autumn and winter turn wet.

Including low-dose metaldehyde pellets in the programme could alleviate the problem, believes Suffolk-based Prime Agriculture agronomist Steve Baldock.

Several years of independent/distributor trials and experience on farm shows these pellets are as effective as the 3% standard in controlling slugs, but can reduce the presence of metaldehyde in water, he explains.

“On farm we’ve had real success using Metamax 1.5% pellets while sticking to good practice as laid out in Metaldehyde Stewardship Group (MSG) guidelines.

Steve Baldock

Steve Baldock

“We’ve also been involved with Essex and Suffolk Water in various catchments using these low-dose pellets plus ferric phosphate and have successfully controlled slugs and kept surface water levels below the 1ppb permitted in drinking water.”

Prime Agriculture has switched almost exclusively to 1.5% metaldehyde pellets.

“We are all aware of the issues with metaldehyde in water,” says Mr Baldock.

“It makes no sense to continue using 3% pellets when you can reduce by half the amount of active ingredient per application while maintaining efficacy.”

It follows that more applications of low-dose pellets can also be made while keeping within MSG guidelines, which state a maximum of 210g/ha of metaldehyde should be applied between 1 August and 31 December.

That equates to just 7kg/ha of standard 3% metaldehyde pellets, but 14kg/ha of the 1.5% pellets.

That allows three applications of 4-5kg/ha, Mr Baldock explains.

Metamax pellets are smaller than the standard pellet and very durable, so these reduced rates still put down 32-40 baiting points/sq m, ensuring effective, long-lasting control and less chance of leaching.

Oilseed rape crops usually receive 5kg/ha at drilling, repeated where necessary a week later.

Rarely, the remaining 4kg/ha available might be needed. Wheat after oilseed rape also gets 5kg/ha at drilling. Fields with a history of the pest get a further dose seven days later. Elsewhere, bait traps are used.

Ferric phosphate pellets complement the programme, says Mr Baldock.

These are used on headlands and in wetter conditions when there is more risk to water or, rarely, when the 210g/ha limit has been reached.

‘Why use more if you don’t need to’

Cultural control is the first line of defence against slugs at A Johnson & Son’s Lodge Farm, Hunston, near Bury St Edmunds, where David Johnson grows a range of combinable crops, mainly for seed.

Oilseed rape, in which slugs flourish, is only grown once every six years at most. All crops are rolled after drilling.

This strategy keeps farm’s lighter, sandy loam soils almost slug-free. But the heavy clay loams need watching.

“We aim to get a fine, firm finish to our seed-beds,” says Mr Johnson.

“Increasingly we are using a Claydon drill which helps.

“We use it for all our oilseed rape and some heavy-land wheat.

“The fields walk drier than those drilled with the combination drill, which also keeps slug numbers in check.”

“We find 4kg/ha of Metamax per application is enough – where slug pressure is lower we put on less.”
David Johnson, Suffolk grower

Wheat after oilseed rape needs pelleting, sometimes on the stubble if populations are high and always after sowing.

“We find 4kg/ha of Metamax per application is enough – where slug pressure is lower we put on less.”

Although tramlines are set at 24m, pellets are applied at 18m centres using a Stocks single-disc applicator mounted on a quad bike.

“Pellets spread a bit thinly towards the edges if you go wider, though a sprayer-mounted applicator would probably work fine.

“But our method is less affected by wind and we can travel at any time.”

Mr Johnson finds the 1.5% pellets have given excellent control over the past 10 years.

“Why use more if you don’t need to? It’s important that we all play our part in stewardship or we could lose metaldehyde altogether.”