Riding the Slime Wave with Dr Jenna Ross

CHAP Innovation Hub Lead, Dr Jenna Ross, is a 2018 Nuffield Farming scholar, and as such, spent 26 weeks travelling the world last year looking at slug control and biological invasions.

Dr Ross’s report was published by the Nuffield Farming Scholarship Trust in October. Here she summarises her findings, outlining the crucial need for controls to this growing problem.



Slugs are important economic pests worldwide, targeting an array of agricultural and horticultural crops. Current methods for controlling slugs in the UK rely heavily on the application of chemical molluscicide pellets, containing either metaldehyde or Iron (Ferric) phosphate.

In December 2018 Defra made the decision to ban the outdoor use of metaldehyde due to its impact on birds and mammals. This ruling was later overturned, after the decision-making process was ruled unlawful, leaving the future of chemical slug control up in the air.

In addition, there are also concerns over biological invasions, especially relating to the Spanish slug, A. vulgaris, which has established itself as a major agricultural pest across much of Europe. Little is known about the impact and extent of the distribution of this slug species in the UK, not to mention other potential slug invasions.


  • Characterise the key slug species in the UK
  • Identify potential slug invasions and their impact on biosecurity
  • Determine direct and indirect economic risk of slugs
  • Review slug monitoring systems
  • Evaluate slug control options
  • Determine the future of malacology
  • Investigate novel commercial opportunities for the utilisation of slugs


  • More than 50 per cent of slug species in the UK are exotic, so it is imperative that biosecurity protocols are developed to prevent further slug invasions;
  • Slugs have a direct economic impact on crop damage, as well as an indirect impact on human and animal health. Slug contamination can lead to the rejection of exported crops and there is also an impact on soil health (through slug control strategies);
  • There is a drive to incorporate technology into slug monitoring systems;
  • With uncertainty over metaldehyde, Iron (Ferric) phosphate may be the only ‘chemical’ control option available in the future;
  • The use of nematode bio-molluscicides is currently not feasible in broadacre crops due to cost, volume of water required, storage and shelf life;
  • Agronomic and cultural practices are playing an increasing role in controlling slugs, with a surge in farmer-led research in this area;
  • Farmers should consider a slug IPM strategy pyramid, tailor-made to each field;
  • The study of malacology appears to be in difficulty, with no clear succession plan in place, and limited funding to share and develop ideas; and
  • Perhaps we are missing an opportunity and we should be farming slugs instead, targeting slugs and their bi-products towards the food, cosmetic and pharmaceutical industries.


National Strategic Action:

  • Conduct a systematic survey to better understand the slug fauna of the UK;
  • Implement biosecurity protocols to prevent future biological invasions of exotic slugs into the UK;
  • Employ an eradication protocol for the Spanish slug, A. vulgaris; and
  • Make changes to the regulatory system to speed up the registration process for new molluscicide products.

Industry and Research Action:

  • Calculate the monetary value of direct and indirect impact of slugs;
  • Develop real-time mobile monitoring and treatment systems for slugs;
  • Invest in the development of new and current chemical, biorational, physical barriers and biological control methods;
  • Develop a system to deliver a slug IPM strategy pyramid that is tailored to each field;
  • Enable scientists to work alongside farmer groups to translate scientific findings into practical outputs; and
  • Investigate opportunities for farming slugs for the food, cosmetic and pharmaceutical industries.

Malacology Knowledge Exchange Action:

  • Re-establish conference opportunities, such as the BCPC Slug and Snail meetings, and secure funding to continue the IOBC Slug and Snail conference, in order to share and develop ideas;
  • Promote malacology to the next generation, and prepare succession plans to avoid the loss of key knowledge; and
  • Encourage citizen science programmes in malacology to engage and educate local communities on slugs, damage and methods of control.

Read her report here…

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Please note, the opinions expressed in this article are the author’s own and do not necessarily reflect the views or opinions of CHAP.