Biological control of slugs and snails with parasitic nematode, Phasmarhabditis hermaprodita
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Slugs (Mollusca: Gastropoda) are considered as important pests of many agricultural and horticultural crops throughout the world.
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Recently, a slug parasitic nematode, P. hermaprodita has been commercialized as a biological molluscicide by MicroBio Ltd, UK and sold under the trade name "Nemaslug".
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Phasmarhabditis hermaprodita as been found to be associated with several different bacteria rather than one particular species but the association with a bacterium, Moraxella oslensis proved to be highly pathogenic to gray garden slug (Deroceras reticulatum) and preferred bacterium for mass production of this nematode in monoxenic culture.
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Like entomopathogenic nematodes, slug parasitic nematode infective juveniles or dauer juveniles move through soil, locate slugs and infect. They penetrate slugs through a natural opening at the backside of the mantle. Once inside, the dauer juveniles release bacterial cells, start feeding on multiplying bacteria and develop into self-fertilizing hermaphrodites. Nematode- bacteria complex can cause the death of the slug within 7-21 days after infection.
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Phasmarhabditis hermaprodita can attack and kill several species of slugs including Arion ater, A. intermedius, A. distinctus, A. silvaticus, D. reticulatum, D. caruanae, Tandonia budapestensis and T. sowerbyi.
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Phasmarhabditis hermaprodita can also parasitize several species of snails including Cernuella virgata, Cochlicella acuta, Helis aspersa, Monacha cantiana, Lymnaea stagnalis and Theba pisana.
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It has been demonstrated that slug parasitic nematodes when applied at the rate of 3x 109 infective juveniles/hectare can give better control of slugs than standard chemical molluscicide, Methiocarb pellets.
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For more information on insect and slug parasitic nematodes read a book "Nematodes As Biocontrol Agents" by Grewal, P.S. Ehlers, R.-U., Shapiro-Ilan, D. (eds.). CAB publishing, CAB International, Oxon.