Potato growers warned over growing slug pressure

Recent rainfall has created the ideal conditions for the increased threat of slug damage for this year’s potato crop with agronomists urging growers to reconsider their treatment plans.

Norfolk-based grower and independent potato specialist, Andrew Alexander warns that this season could be a high pressure year. “Over the last two seasons slug pressure has not been horrendous by any means, with slug pelleting applications around the 50% level.

“Slugs were dormant, retreating as far as 1m deep into the soil during last summer’s hot weather,” notes Mr Alexander, referring to sightings in pits dug last year.

Robert Boothman, agronomist and partner at Boothmans Agriculture in Lincolnshire warns that slug damage can be very costly to potato crops, specifically those grown for the packaging and processing market, which can see loads showing over 5% damage, which includes bruising and hollowing, being rejected.

Crops under the most pressure will be those planted in high levels of organic matter following oilseed rape and into cloddy ridges as both provide the perfect habitat for slugs.

“Some varieties are also more susceptible to slug damage, Maris Piper is one example,” says Greg Dawson, agronomist for Scottish Agronomy.

Mr Alexander urges against adopting a pelleting programme as a matter of course, advocating the use of a risk management approach and test baiting to inform decisions. “It is important to ensure we are not treating and using metaldehyde quantities unnecessarily, both from a stewardship point of view but also from a financial point of view, avoiding unnecessary spend.

With pellets, Mr Boothman has three key points for growers to consider: quality, quantity and application.

“This year I would recommend going in early with a good quality pellet applied with the first blight spray,” says Mr Boothman. “I would advise opening with a 3% methiocarb pellet at 5kg/ha.”

This means a pellet application at the early rosette stage, targeting any slugs that have emerged in the recent, brief, warm spell.

Growers also need to consider an application at desiccation to control any slugs remaining in ridges that could still damage tubers.

Mr Boothman advises investing in the best quality pellet available, choosing a product with a hard outer shell that can provide the maximum target for slugs while lasting for a long time on the soil surface.

“Application is also important, new applicators are much more effective at distributing pellets without damaging them,” he adds. Cracking the pellet’s surface during application reduces it effectiveness.

Scottish Agronomy urge against adopting a pelleting programme as a matter of course

Metaldehyde stewardship

  • Total annual use should not exceed 700g/ha of the active
  • A single application should not exceed 210g/ha
  • Maximum total dose from 1 August to 31 December is 210g/ha of metaldehyde
  • No pellets should be applied within 6m of watercourses.
  • Do not apply during heavy rainfall or when drains are running.

More information can be found online at http://www.getpelletwise.co.uk/

Source: Get Pellet Wise campaign

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