Growers face big restrictions in the use of a key ingredient for controlling slugs at a crucial time of year, Bayer Crop Sciences has warned.

July is a key month for using slug pellets on potato crops – this will be extra challenging this year as growers cope with reduced metaldehyde rates.

Earlier this year some metaldehyde products were re-approved by pesticide chiefs, said Bayer Crop Sciences product manager Peter Stacey, but use on potatoes was restricted to a maximum individual dose of 350g of active ingredient per hectare and a maximum total dose per crop of 700g

The restrictions effectively rule out the “little -and-often approach” of applying mini metaldehyde pellets with every blight spray.

Trial group Scottish Agronomy said growers could probably improve results by switching to a methiocarb-based slug control strategy. “We have consistently seen greater activity from methiocarb,” said trialler Eric Anderson. “This overides the higher number of baiting points delivered by some methaldehyde produces.

“The optimum time to begin slug control is at 50 to 75 per cent canopy closure, which crops usually reach early in July. At this time the canopy is starting to create moist slug-conducive  conditions on the soil surface but still allows uniform pellet distribution.

“Full rate application of methiocarb pellet, such as Draza forte at 3.75kg/ha will have the biggest initial impact on slug population at this timing.”