With high slug populations and continued showers, potato growers are urged to reduce numbers with a molluscicide application before crops reach canopy closure this season.

Slug pressure was very high in the autumn after favourable breeding conditions in September and October.

The subsequent mild, wet winter and regular rain during spring has done little to dent the extremely high numbers on land earmarked for potato planting.

This has led Shropshire-based independent potato consultant Graeme Ditty to recommend slug pellets two to three weeks earlier than usual in susceptible varieties like Maris Piper to try to reduce numbers.

Other factors in his risk assessment include soil type and whether oilseed rape or cover crops feature in the rotation, as these are making 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.

“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,” says Graeme.

Ballistic properties

 With many potato growers spreading pellets from their sprayers, sometimes to 36m, he recommends using a robust pellet with good ballistic properties to ensure adequate coverage across the machine’s width.

Certis Belchim’s technical manager James Cheesman agrees and says it is important to know both the capabilities of your applicator and product to ensure that the optimum spread pattern is achieved.

The firm’s online Calibration Wizard tool allows operators to check both, with a twin disc spreader like a StocksAg Fanjet Duo, one example of a typical applicator used to spread a standard sized pellet like Sluxx HP to 36m.

James adds that a wet processed pasta-based formulation like Sluxx HP also offers the durability required in moist conditions beneath potato canopies, particularly where irrigated.

“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.”