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High slug populations and continued showers during June saw potato growers urged to apply molluscicides before crops reach the  canopy stage. Slug pressure has... Target slugs early in challenging season

High slug populations and continued showers during June saw potato growers urged to apply molluscicides before crops reach the  canopy stage.

Slug pressure has remained high since last autumn after favourable breeding conditions in September and October. The subsequent mild, wet winter and spring did little to dent slug populations on land destined for potato planting.

Independent potato consultant Graeme Ditty suggested growers should apply slug pellets two to three weeks earlier than usual in susceptible crops like Maris Piper to get on top of the problem.

Risk assessment

Other factors in his risk assessment include soil type and whether oilseed rape or cover crops feature in the rotation. Both have made slug pressure worse, particularly where brassicas are part of the cover crop mix.

After significant amounts of winter and spring rain, some potato seedbeds have been forced on more bodied land and cloddy ridges will exacerbate the slug threat, explained Mr Ditty.

“A large percentage of my potato crops will receive at least one pellet application before plants meet between the rows, depending on variety and situation. In the riskiest spots, two applications might be justified.

“It’s a numbers game and we need to knock them back if we can. I just don’t want to take any chances this year with pressure so high.”

Ballistic properties

With many potato growers spreading pellets from their sprayers, Mr Ditty recommends using a robust pellet with good ballistic properties to ensure adequate coverage right across the machine’s width.

Certis Belchim technical manager James Cheesman agrees. He says it is important to know the capability of the applicator and qualities of the slug pellet to achieve the optimum spread pattern.

The firm’s online Calibration Wizard tool allows sprayer operators to check both. A twin disc spreader like a StocksAg Fanjet Duo, for example, will typically spread a standard sized pellet like Sluxx HP to 36m.

A wet processed pasta-based formulation like Sluxx HP also offers the durability required in moist conditions beneath potato canopies, particularly where irrigated, says Mr Cheesman.

“This ensures that the pellets are working for longer than others when applied just before canopy closure.

“Growers should then keep an eye on populations throughout the season and ensure pellets are reapplied when fully developed tubers are vulnerable to slug attack during and after the haulm destruction process.”