Essential oils are being increasingly utilised as a biorational element in integrated pest management regimes. Whereas there has been much research on the effects of these oils on mortality and behaviour of pestiferous molluscs, insects and nematodes, there has (to the present authors' knowledge) been no research into their effects on the mortality and behaviour of beneficial nematodes. We address this lacuna by conducting laboratory assays on the behaviour (thrashing assays) and mortality of 13 essential oils plus controls of Tween and water on the malacophagous nematode Phasmarhabditis hermaphrodita and two species of entomopathogenic nematodes, namely: Steinernema feltiae and Heterorhabditis bacteriophora. Mortality results showed an "all or nothing" response with only three oils-pine oil, peppermint and lemongrass-displaying intermediate mortalities. Also, toxicity of essential oils was conserved across phylogenetically quite distinct beneficial nematode species with oil toxicity largely being repeated across the three beneficial nematodes. Thrashing assays confirmed the toxic effects of certain oils. We recommend that the effects of essential oils be tested on beneficial organisms in ecosystems before choices are made over which oils should be used. The present paper highlights some oils which are not toxic to beneficial nematodes but may affect their behaviour. Research should focus on these oils as part of a biorational control programme for pestiferous molluscs and insects.
Several slug species are highly pestiferous and threaten global sustainable agriculture. Current control methods rely heavily on metaldehyde pellets, which are often ineffective, harm nontarget organisms and have been banned in some countries. A viable alternative is the parasitic nematode Phasmarhabditis hermaphrodita (and recently P. californica), which has been formulated into a biological control agent (Nemaslug®) to control slugs across northern Europe. Nematodes are mixed with water and applied to soil where they seek out slugs, penetrate behind the mantle and kill them in 4–21 days. Phasmarhabditis hermaphrodita has been on the market since 1994 and since then there has been ample research on its use. Here we review the research carried out on P. hermaphrodita over the last 30 years since its development and release as a commercial product. We provide information on life cycle, worldwide distribution, history of commercialisation, gastropod immunity, host range, ecological and environmental factors that affect its success in the field, bacterial relationships, and summarise results of field trials. Finally, we suggest future directions for P. hermaphrodita research (and other Phasmarhabditis species) to enhance its use as a biological control agent to control slugs for the next 30 years. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
There is very little published information about how to culture slugs. There are at least 36 species of slug in the UK (Anderson, 2008) and as many as 44 (Rowson et al., 2014), many of which are nonnative (Cameron, 2016). They are important in terms of causing economic damage to crops (South, 1992), as well as hosts for medically important parasites such as Angiostrongylus cantonensis (Barratt et al., 2016). The aim of our study was to discover whether three species of slug, Deroceras invadens Reise, Hutchinson, Schunack & Schlitt 2011, Arion hortensis Férussac 1819 and Ambigolimax valentianus (Férussac 1822), could be cultured and mated to produce offspring and whether these offspring would be viable enough to produce more progeny. Ultimately, by providing information on how to maintain and breed slugs through several generations, perhaps a 'model slug' could be developed, which could benefit an array of subjects including genetics, genomics and developmental biology.Preliminary observations in the laboratory showed that D. invadens and A. hortensis preferred to lay eggs in peat-free compost (SylvaGrow ® , Melcourt, UK) as compared to garden bed or turf soil. Observations also demonstrated differences in egg development for the three species at different temperatures. Specifically, D. invadens at 10 °C, and A. hortensis and A. valentianus at 15 °C produced the highest level of viable eggs, presumably due to differences in the ecological niches they inhabit. The slugs were collected from a garden in Maghull, Liverpool (UK OS grid reference SD373027). They were kept in nonairtight plastic boxes (35 x 23 x 22 cm) at 5 °C with moistened paper and fed lettuce ad libitum for 1 week before use to check for any signs of ill health. Compost (10-15% moisture content) was added to a
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