Is a combination of different natural substances suitable for slug (Arion spp.) control?

Abstract

In a laboratory study we investigated the contact and barrier efficacy of different natural substances (wood ash, sawdust, hydrated lime, and diatomaceous earth) against slugs of the genus Arion, an important agricultural pest. Natural substances were tested individually and in combination with each other. The experiment was carried out in plastic petri dishes and in glass insectaria. Moistened tampons and fresh leaves of lettuce were placed into both experimental arenas. The slugs were starved for 48 hours prior to the experiment. Six categories of behaviour were identified for slugs in the presence of the natural substances: (1) slug survived the experiment, (2) slug died during the experiment, (3) slug crossed the barrier, (4) slug did not cross the barrier, (5) slug fed on the lettuce, and (6) slug did not feed on the lettuce. The effect of different treatments (natural substances) was significant. The results of our study have shown that hydrated lime had the best contact efficacy on slugs (the mortality of slugs was 100%), both individually and in combination with other substances. The treatments with hydrated lime also proved to be the most efficient barrier preventing slugs from feeding on lettuce. Hydrated lime shows great potential in Arion control in our investigation; however, further research is needed to investigate the practical value (how to avoid the problem when the substance becomes wet), safety and economics of hydrated lime used in this way.

Assessment of Barrier Materials to Protect Plants from Florida Leatherleaf Slug (Mollusca: Gastropoda: Veronicellidae)

“…The recommendation to use this material to kill molluscs, or to deter their feeding on foliage, lacks consistent scientific support. Recently, the lack of diatomaceous earth efficacy also was noted by Laznik and Trdan (2016), although Ciomperlik et al (2013) observed some bioactivity depending on the species of snails evaluated. Even with insects, diatomaceous earth is not always an effective insecticide (Martindale & Newlands 1981).…”

“…However, Korunić (1997) noted that the toxicity of diatomaceous earth to insects can vary greatly depending on such factors as pH, shape and size of particles, size distribution, SiO 2 content, adsorption, and whether their origin was freshwater or marine diatoms. Laznik and Trdan (2016) were similarly unable to demonstrate significant toxic effects on molluscs when treated with diatomaceous earth. Silica also occurs naturally in some plants where it can have a major role in defense against insect herbivory (Reynolds et al 2009).…”

“…If a barrier is desired to keep slugs from accessing plants, sulfur or hydrated lime appear to be suitable choices. Laznik and Trdan (2016) observed that hydrated lime was an effective barrier treatment, but did not evaluate sulfur. Due to the ability of lime and sulfur to affect soil pH, it probably would be advisable to use lime where the soil is acidic, and sulfur where it is alkaline.…”

“…Thompson et al (2005) found that copper hydroxide affected feeding by Deroceras laeve (Müller, 1774) (Gastropoda: Agrolimacidae) and Ambiogolimax valentianus (Lehmannia valentiana) (Ferussac, 1822) (Gastropoda: Limacidae) in choice tests; similarly, Capinera & Dickens (2016) reported that 2 species of snails (Ventridens demissus [A. Binney, 1843] [Gastropoda: Zonitidae] and Lissachatina fulica [Férussac, 1821] [Gastropoda: Achtinidae]) and 2 slugs (Deroceras laeve and Leidyula floridana (Leidy, 1851] [Gastropoda: Veronicellidae]) were deterred from feeding by copper hydroxide in choice-and no-choice tests. Laznik and Trdan (2016) reported that hydrated lime and wood ash could be used to form a barrier and provide some protection of leaf tissue from herbivory by Arion slugs (Gastropoda: Arionidae). Lindqvist et al (2010) found that birch tar oil would repel the snail Arianta arbustorium (Linnaeus, 1758) (Gastropoda: Helicidae) and the slug Arion lusitanicus Mabille, 1868 (Gastropoda: Arionidae).…”

Contact Efficacy of Different Wood Ashes against Spanish Slug, Arion vulgaris (Gastropoda: Arionidae)

“…Recently, new molluscicidal substances that are environmentally acceptable have been proposed [22,24,25]. New natural compounds are characterized as selective and highly toxic to target pests, safe for non-target organisms, low cost, and biodegradable [1,25]. The use of wood ash has been noted among these compounds [2,25].…”