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A review of terrestrial slug and snail species of potential threat to plant health in Britain - PH04103

It is estimated that at least 30% of the British slug and snail fauna is non-native and arrived with human assistance. While not all of these introduced species are plant pests, many are a potential threat to plants. This includes species such as Arion vulgaris, Deroceras invadens and Tandonia cristata, all of which are established in Britain and are plant pests in multiple countries. Species such as Arion vulgaris also pose a threat to our native biodiversity due to their ability to hybridise and potentially outcompete our native slug species. Invasive species of slug and snail can also be human and livestock disease vectors. Further plant pest species are expected to continue to arrive in Britain, such as Tandonia kusceri, which is a pest of root vegetables expanding its range throughout Europe and the USA. More exotic species such as Achatinidae (giant African land snails) and the Veronicellidae (pancake slugs) pose a threat on multiple fronts globally to plant and human health. While these subtropical species establishment in Britain is currently limited by climate, research in the USA is showing that temperature tolerance may be less restrictive on survival than originally thought.

While slugs and snails are poor at active dispersal, they are able to use passive dispersal such as the trade of goods to colonise different areas. The horticultural plant trade has been identified globally as an important vector in the spread of alien slug and snail species. The polyphagous nature of many species combined with other life history traits, such as surviving long periods of aestivation, means that slug and snail species can be transported easily with many commodities and their associated conveyances and packaging material.

Detailed knowledge and understanding of pest species of slugs and snails that are likely to be associated with trade pathways and subsequently establish in the UK is lacking. The UK and many parts of Europe do not have detailed interception data on terrestrial slugs and snails entering the country via trade routes. However, countries such as the USA, New Zealand, South Africa and Australia do maintain interception data or have published peer reviewed literature detailing species introductions and potential or known pathways. The purpose of this work is to use this literature to assess the likelihood of damaging terrestrial slug and snail species of arriving in Britain and in broad terms, their potential to cause economic, social or environmental impacts to plant health. The focus will be on terrestrial species of slug and snail as these are most likely to have an impact on plant health. The project will not generate detailed pest risk analyses but will provide data to inform such analyses.
To create a ranked list of terrestrial species/genera/families of slug and snail likely to establish in the UK with potential to cause economic, social or environmental impacts from a plant health perspective, with the top ten explored in detail.

Summarise distribution, current/potential impacts and pathways of introduction for each of these top ten species/genera/families.

Identify areas where the UK needs to improve its capability to identify molluscs and potential ways in which this could be implemented
Time-Scale and Cost
From: 2021

To: 2022

Cost: £9,262
Contractor / Funded Organisations
The Royal Horticultural Society
Plant Pests and Diseases              
Fields of Study
Plant Health