A Literature Review of Biological and Bio-Rational Control Strategies for Slugs: Current Research and Future Prospects

Abstract

Terrestrial gastropod molluscs (slugs and snails) (Mollusca: Gastropoda) cause significant crop damage around the world. There is no formal approach for differentiating between slugs and snails; however, an organism is usually considered a slug when there is no external shell, or when the shell is small in comparison to the body, and a snail when there is a large external shell. Although snails are an important pest of many crops, this review focuses on slug pests and their nonchemical control measures. A recent study by the UK Agriculture and Horticulture Development Board concluded that the failure to control slugs could cost the UK agriculture industry over GBP 100 million annually, with similar figures reported around the world. Whilst slugs are mostly controlled using chemical molluscicide products, some actives have come under scrutiny due to their detrimental environmental effects and impact on nontarget organisms. This has resulted in the ban of actives such as methiocarb in the UK and EU, and, more recently, the ban of metaldehyde in the UK. Therefore, there is an urgent need to find alternative and effective nontoxic solutions in the interest of global food security. In this paper, we have integrated extant literature on the three main biological control agents of slugs, namely nematodes, carabid beetles and sciomyzid flies, and various promising bio-rational slug control strategies. The review also highlights current research gaps and indicates some relevant potential future directions towards developing environmentally benign slug control solutions.

Reducing the Application Rate of Molluscicide Pellets for the Invasive Spanish Slug, Arion vulgaris

“…Until sufficient effective nontoxic solutions are identified [ 14 ], our results suggest that new applications of molluscicides could be useful; slugs should be monitored and the application rate should be adjusted according to the number of slugs and to the established tendency of slugs to eat a certain amount of specific molluscicide pellets. Especially since we get a significant effect of time, this becomes even more important as it shows that in the second half of the summer, before the laying of eggs, the roughness of the slugs naturally decreases, and, therefore, the amount of poison eaten is reliably lower.…”

“…Therefore, the excessive application of molluscicides should be avoided. There are quite efficient non-chemical and biocontrol methods widely used in EU, such as physical barriers (diatomaceous earth, hydrated lime, sulfur, fumed silica, wood ash) [ 12 , 13 ], agronomic practices, and biological (nematodes) and bio-rational control [ 14 ], but it is often simpler to apply chemical methods.…”

Thirty years of slug control using the parasitic nematode Phasmarhabditis hermaphrodita and beyond

“…Several slug species are highly pestiferous and pose a significant global threat to agriculture, horticulture and floriculture 1 . Slugs cause crop damage by eating seeds, stems, growing points and leaves, leading to a reduction in growth 2,3 .…”

Entomological Investigation of the Main Entomatic Adversities for Terrestrial Gastropods Helix aspersa Müller (Mollusca Gastropoda Pulmonata): A Preliminary Study in Sardinian Heliciculture Farms

“…Most of the studies focus on the snail’s role as a harmful parasite for agriculture. Snails constitute a serious menace to agricultural production, resulting in significant economic losses for a wide range of crops (e.g., rape, vegetables, legumes, cereals, and fruits) [ 14 ]. The welfare and health of bred gastropod mollusks (snails and slugs) have not been studied in depth.…”